Internet Engineering Task Force                                MMUSIC WG
Internet Draft                                            H. Schulzrinne
                                                             Columbia U.
                                                                  A. Rao
                                                                   Cisco
                                                             R. Lanphier
                                                            RealNetworks
                                                           M. Westerlund
                                                                Ericsson

draft-ietf-mmusic-rfc2326bis-01.txt
June 06,

draft-ietf-mmusic-rfc2326bis-02.txt
November 01, 2002
Expires: December, 2002 April, 2003

                  Real Time Streaming Protocol (RTSP)

STATUS OF THIS MEMO

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference mate-
   rial or to cite them other than as "work in progress".

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   To view the list Internet-Draft Shadow Directories, see
   http://www.ietf.org/shadow.html.

Abstract

   This memorandum is a revision of RFC 2326, which is currently a Pro-
   posed Standard.

   The Real Time Streaming Protocol, or RTSP, is an application-level
   protocol for control over the delivery of data with real-time proper-
   ties. RTSP provides an extensible framework to enable controlled, on-
   demand delivery of real-time data, such as audio and video. Sources
   of data can include both live data feeds and stored clips. This pro-
   tocol is intended to control multiple data delivery sessions, provide
   a means for choosing delivery channels such as UDP, multicast UDP and
   TCP, and provide a means for choosing delivery mechanisms based upon
   RTP (RFC 1889).

1 Introduction

1.1 The Update of the Specification                                      |

   This is the draft to an update of the RTSP which currently is a pro-  |
   posed standard defined in  [21]. During the years since RTSP was pub- |
   lished many flaws has been found. This draft tries to address these.  |
   The work is not yet completed to get all known issues resolved.       |

   The goal is to progress RTSP to draft standard. If that is possible   |
   without first publishing it as a proposed standard is not yet deter-  |
   mined, as it depends on the changes necessary to make the protocol    |
   work.                                                                 |

   See the list of changes in chapter  F to see what has been addressed. |
   The currently open issues are listed in chapter  E                    |

   There is currently a list of reported bugs available at "http://rtsp- |
   spec.sourceforge.net". This list should be taken into account when    |
   reading this specification. A lot of these bugs are addressed but not |
   yet all. Please comment on unresolved ones to give your view.         |

   Another way of giving input on this work is to send e-mail to the     |
   MMUSIC WG's mailing list mmusic@ietf.org and the authors.             |

   Take special notice of the following:                                 |

     + The example section  14 has not yet been revised as the changes   |
       to protocol has not been completed.                               |

     + The BNF chapter  16 has neither been compiled completely.         |

1.2 Purpose

   The Real-Time Streaming Protocol (RTSP) establishes and controls
   either a single or several time-synchronized streams of continuous
   media such as audio and video. It does not typically deliver the con-
   tinuous streams itself, although interleaving of the continuous media
   stream with the control stream is possible (see Section 10.13). In
   other words, RTSP acts as a "network remote control" for multimedia
   servers.

   The set of streams to be controlled is defined by a presentation
   description. This memorandum does not define a format for a presenta-
   tion description.

   There is no necessity for a notion of an RTSP connection; instead, a
   server maintains a session labeled by an identifier. An RTSP session
   is in no way normally not tied to a transport-level connection such as a TCP
   connection. During an RTSP session, an RTSP client may open and close
   many reliable trans-
   port transport connections to the server to issue RTSP
   requests. Alternatively, it may use a connectionless transport protocol proto-
   col such as UDP.

   The streams controlled by RTSP may use RTP [1], but the operation of
   RTSP does not depend on the transport mechanism used to carry contin-
   uous media.

   The protocol is intentionally similar in syntax and operation to
   HTTP/1.1 [26] so that extension mechanisms to HTTP can in most cases
   also be added to RTSP. However, RTSP differs in a number of important
   aspects from HTTP:

     + RTSP introduces a number of new methods and has a different pro-
       tocol identifier.

     + An RTSP server needs to maintain state by default in almost all
       cases, as opposed to the stateless nature of HTTP.

     + Both an RTSP server and client can issue requests.

     + Data is usually carried out-of-band by a different protocol. (There
       Session descriptions is an
       exception to this.) one possible exception.

     + RTSP is defined to use ISO 10646 (UTF-8) rather than ISO 8859-1,
       consistent with current HTML internationalization efforts [3].

     + The Request-URI always contains the absolute URI. Because of
       backward compatibility with a historical blunder, HTTP/1.1 [26]
       carries only the absolute path in the request and puts the host
       name in a separate header field.

          This makes "virtual hosting" easier, where a single host
          with one IP address hosts several document trees.

   The protocol supports the following operations:

     Retrieval of media from media server: The client can request a pre-
          sentation description via HTTP or some other method. If the
          presentation is being multicast, the presentation description
          contains the multicast addresses and ports to be used for the
          continuous media.  If the presentation is to be sent only to
          the client via unicast, the client provides the destination
          for security reasons.

     Invitation of a media server to a conference: A media server can be
          "invited" to join an existing conference, either to play back
          media into the presentation or to record all or a subset of
          the media in a presentation. This mode is useful for dis-
          tributed teaching applications. Several parties in the confer-
          ence may take turns "pushing the remote control buttons".

     Addition of media to an existing presentation: Particularly for
          live presentations, it is useful if the server can tell the
          client about additional media becoming available.

   RTSP requests may be handled by proxies, tunnels and caches as in
   HTTP/1.1 [26].

1.2

1.3 Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [4].

1.3

1.4 Terminology

   Some of the terminology has been adopted from HTTP/1.1 [26]. Terms
   not listed here are defined as in HTTP/1.1.

     Aggregate control: The control of the multiple streams using a sin-
          gle timeline by the server. For audio/video feeds, this means
          that the client may issue a single play or pause message to
          control both the audio and video feeds.                        |

     Aggregate control URI: The URI that represents the whole aggregate. |
          Normally specified in the session description.

     Conference: a multiparty, multimedia presentation, where "multi"
          implies greater than or equal to one.

     Client: The client requests continuous media data service from the media server.    |

     Connection: A transport layer virtual circuit established between
          two programs for the purpose of communication.

     Container file: A file which may contain multiple media streams
          which often comprise a presentation when played together. RTSP
          servers may offer aggregate control on these files, though the
          concept of a container file is not embedded in the protocol.

     Continuous media: Data where there is a timing relationship between
          source and sink; that is, the sink must reproduce the timing
          relationship that existed at the source. The most common exam-
          ples of continuous media are audio and motion video. Continu-
          ous media can be real-time (interactive), where there is a
          "tight" timing relationship between source and sink, or
          streaming (playback), where the relationship is less strict.

     Entity: The information transferred as the payload of a request or
          response. An entity consists of metainformation in the form of
          entity-header fields and content in the form of an entity-
          body, as described in Section 8.

     Feature tag: A tag representing a certain set of functionality,
          i.e. a feature.

     Media initialization: Datatype/codec specific initialization.  This
          includes such things as clockrates, color tables, etc. Any
          transport-independent information which is required by a
          client for playback of a media stream occurs in the media ini-
          tialization phase of stream setup.

     Media parameter: Parameter specific to a media type that may be
          changed before or during stream playback.

     Media server: The server providing playback or recording services
          for one or more media streams. Different media streams within
          a presentation may originate from different media servers. A
          media server may reside on the same or a different host as the
          web server the presentation is invoked from.

     Media server indirection: Redirection of a media client to a dif-
          ferent media server.

     (Media) stream: A single media instance, e.g., an audio stream or a
          video stream as well as a single whiteboard or shared applica-
          tion group. When using RTP, a stream consists of all RTP and
          RTCP packets created by a source within an RTP session. This
          is equivalent to the definition of a DSM-CC stream([5]).

     Message: The basic unit of RTSP communication, consisting of a
          structured sequence of octets matching the syntax defined in
          Section 15 16 and transmitted via a connection or a connection-
          less protocol.

     Non-Aggregated Control: Control of a single media stream.  Only
          possible in RTSP sessions with a single media.

     Participant: Member of a conference. A participant may be a
          machine, e.g., a media record or playback server.

     Presentation: A set of one or more streams presented to the client
          as a complete media feed, using a presentation description as
          defined below. In most cases in the RTSP context, this implies
          aggregate control of those streams, but does not have to.

     Presentation description: A presentation description contains
          information about one or more media streams within a presenta-
          tion, such as the set of encodings, network addresses and
          information about the content. Other IETF protocols such as
          SDP (RFC 2327 [24]) use the term "session" for a live presen-
          tation. The presentation description may take several differ-
          ent formats, including but not limited to the session descrip-
          tion format SDP.

     Response: An RTSP response. If an HTTP response is meant, that is
          indicated explicitly.

     Request: An RTSP request. If an HTTP request is meant, that is
          indicated explicitly.

     RTSP session: A complete RTSP "transaction", e.g., the viewing of state established on a
          movie. A session typically consists of RTSP server by a client setting up with |
          an SETUP request. The RTSP session exist until it either time- |
          outs or is explicitly removed by a
          transport mechanism for the continuous TEARDOWN request.  The ses- |
          sion contains state about which media stream (SETUP),
          starting the stream with PLAY resources that can be    |
          played or RECORD, recorded, and closing the
          stream with TEARDOWN. their transport.

     Transport initialization: The negotiation of transport information
          (e.g., port numbers, transport protocols) between the client
          and the server.

1.4

1.5 Protocol Properties

   RTSP has the following properties:

     Extendable: New methods and parameters can be easily added to RTSP.

     Easy to parse: RTSP can be parsed by standard HTTP or MIME parsers.

     Secure: RTSP re-uses web security mechanisms, either at the trans-
          port level (TLS, RFC 2246 [27]) or within the protocol itself.
          All HTTP authentication mechanisms such as basic (RFC 2616
          [26]) and digest authentication (RFC 2069 [6]) are directly
          applicable.

     Transport-independent: RTSP may use either an unreliable datagram
          protocol (UDP) (RFC 768 [7]), a reliable datagram protocol
          (RDP, RFC 1151, not widely used [8]) or a reliable stream pro-
          tocol such as TCP (RFC 793 [9]) as it implements application-
          level reliability.

     Multi-server capable: Each media stream within a presentation can
          reside on a different server. The client automatically estab-
          lishes several concurrent control sessions with the different
          media servers.  Media synchronization is performed at the
          transport level.

     Control of recording devices: The protocol can control both record-
          ing and playback devices, as well as devices that can alter-
          nate between the two modes ("VCR").

     Separation of stream control and conference initiation: Stream con-
          trol is divorced from inviting a media server to a conference.
          In particular, SIP [10] or H.323 [28] may be used to invite a
          server to a conference.

     Suitable for professional applications: RTSP supports frame-level
          accuracy through SMPTE time stamps to allow remote digital
          editing.

     Presentation description neutral: The protocol does not impose a
          particular presentation description or metafile format and can
          convey the type of format to be used. However, the presenta-
          tion description must contain at least one RTSP URI.

     Proxy and firewall friendly: The protocol should be readily handled
          by both application and transport-layer (SOCKS [11]) fire-
          walls. A firewall may need to understand the SETUP method to
          open a "hole" for the UDP media stream.

     HTTP-friendly: Where sensible, RTSP reuses HTTP concepts, so that
          the existing infrastructure can be reused. This infrastructure
          includes PICS (Platform for Internet Content Selection
          [12,13]) for associating labels with content. However, RTSP
          does not just add methods to HTTP since the controlling
          continuous con-
          tinuous media requires server state in most cases.

     Appropriate server control: If a client can start a stream, it must
          be able to stop a stream. Servers should not start streaming
          to clients in such a way that clients cannot stop the stream.

     Transport negotiation: The client can negotiate the transport
          method prior to actually needing to process a continuous media
          stream.

     Capability negotiation: If basic features are disabled, there must
          be some clean mechanism for the client to determine which
          methods are not going to be implemented. This allows clients
          to present the appropriate user interface. For example, if
          seeking is not allowed, the user interface must be able to
          disallow moving a sliding position indicator.

     An earlier requirement in RTSP was multi-client capability.
     However, it was determined that a better approach was to make
     sure that the protocol is easily extensible to the multi-
     client scenario. Stream identifiers can be used by several
     control streams, so that "passing the remote" would be possi-
     ble. The protocol would not address how several clients nego-
     tiate access; this is left to either a "social protocol" or
     some other floor control mechanism.

1.5

1.6 Extending RTSP

   Since not all media servers have the same functionality, media
   servers by necessity will support different sets of requests. For
   example:

     + A server may only be capable of playback thus has no need to sup-
       port the RECORD request.

     + A server may not be capable of seeking (absolute positioning) if
       it is to support live events only.

     + Some servers may not support setting stream parameters and thus
       not support GET_PARAMETER and SET_PARAMETER.

   A server SHOULD implement all header fields described in Section 12.

   It is up to the creators of presentation descriptions not to ask the
   impossible of a server. This situation is similar in HTTP/1.1 [26],
   where the methods described in [H19.5] are not likely to be supported
   across all servers.

   RTSP can be extended in three ways, listed here in order of the mag-
   nitude of changes supported:

     + Existing methods can be extended with new parameters, as long as
       these parameters can be safely ignored by the recipient. (This is
       equivalent to adding new parameters to an HTML tag.) If the
       client needs negative acknowledgement when a method extension is
       not supported, a tag corresponding to the extension may be added
       in the Require: field (see Section 12.32).

     + New methods can be added. If the recipient of the message does
       not understand the request, it responds with error code 501 (Not
       Implemented) and the sender should not attempt to use this method
       again.  A client may also use the OPTIONS method to inquire about
       methods supported by the server. The server SHOULD list the meth-
       ods it supports using the Public response header.

     + A new version of the protocol can be defined, allowing almost all
       aspects (except the position of the protocol version number) to
       change.

1.6

1.7 Overall Operation

   Each presentation and media stream may be identified by an RTSP URL.
   The overall presentation and the properties of the media the presen-
   tation is made up of are defined by a presentation description file,
   the format of which is outside the scope of this specification.  The
   presentation description file may be obtained by the client using
   HTTP or other means such as email and may not necessarily be stored
   on the media server.

   For the purposes of this specification, a presentation description is
   assumed to describe one or more presentations, each of which main-
   tains a common time axis. For simplicity of exposition and without
   loss of generality, it is assumed that the presentation description
   contains exactly one such presentation. A presentation may contain
   several media streams.

   The presentation description file contains a description of the media
   streams making up the presentation, including their encodings, lan-
   guage, and other parameters that enable the client to choose the most
   appropriate combination of media. In this presentation description,
   each media stream that is individually controllable by RTSP is iden-
   tified by an RTSP URL, which points to the media server handling that
   particular media stream and names the stream stored on that server.
   Several media streams can be located on different servers; for exam-
   ple, audio and video streams can be split across servers for load
   sharing.  The description also enumerates which transport methods the
   server is capable of.

   Besides the media parameters, the network destination address and
   port need to be determined. Several modes of operation can be distin-
   guished:

     Unicast: The media is transmitted to the source of the RTSP
          request, with the port number chosen by the client. Alterna-
          tively, the media is transmitted on the same reliable stream
          as RTSP.

     Multicast, server chooses address: The media server picks the mul-
          ticast address and port. This is the typical case for a live
          or near-media-on-demand transmission.

     Multicast, client chooses address: If the server is to participate
          in an existing multicast conference, the multicast address,
          port and encryption key are given by the conference descrip-
          tion, established by means outside the scope of this specifi-
          cation.

1.7

1.8 RTSP States

   RTSP controls a stream which may be sent via a separate protocol,
   independent of the control channel. For example, RTSP control may
   occur on a TCP connection while the data flows via UDP. Thus, data
   delivery continues even if no RTSP requests are received by the media
   server. Also, during its lifetime, a single media stream may be con-
   trolled by RTSP requests issued sequentially on different TCP connec-
   tions. Therefore, the server needs to maintain "session state" to be
   able to correlate RTSP requests with a stream. The state transitions
   are described in Section Appendix A.

   Many methods in RTSP do not contribute to state. However, the follow-
   ing play a central role in defining the allocation and usage of
   stream resources on the server: SETUP, PLAY, RECORD, PAUSE, and TEAR-
   DOWN.

     SETUP: Causes the server to allocate resources for a stream and
          start
          create an RTSP session.

     PLAY and RECORD: Starts data transmission on a stream allocated via
          SETUP.

     PAUSE: Temporarily halts a stream without freeing server resources.

     TEARDOWN: Frees resources associated with the stream.  The RTSP
          session ceases to exist on the server.

          RTSP methods that contribute to state use the Session header
          field (Section 12.37) to identify the RTSP session whose state
          is being manipulated. The server generates session identifiers
          in response to SETUP requests (Section 10.4).

1.8

1.9 Relationship with Other Protocols

   RTSP has some overlap in functionality with HTTP. It also may inter-
   act with HTTP in that the initial contact with streaming content is
   often to be made through a web page. The current protocol specifica-
   tion aims to allow different hand-off points between a web server and
   the media server implementing RTSP. For example, the presentation
   description can be retrieved using HTTP or RTSP, which reduces
   roundtrips in web-browser-based scenarios, yet also allows for stan-
   dalone RTSP servers and clients which do not rely on HTTP at all.

   However, RTSP differs fundamentally from HTTP in that most data
   delivery takes place out-of-band in a different protocol. HTTP is an asymmet-
   ric
   asymmetric protocol where the client issues requests and the server
   responds. In RTSP, both the media client and media server can issue
   requests. RTSP requests are also not stateless; they may set parame-
   ters and continue to control a media stream long after the request
   has been acknowledged.

     Re-using HTTP functionality has advantages in at least two
     areas, namely security and proxies. The requirements are very
     similar, so having the ability to adopt HTTP work on caches,
     proxies and authentication is valuable.

   While most real-time media will use RTP as a transport protocol, RTSP
   is not tied to RTP.

   RTSP assumes the existence of a presentation description format that
   can express both static and temporal properties of a presentation
   containing several media streams.

2 Notational Conventions

   Since many of the definitions and syntax are identical to HTTP/1.1,
   this specification only points to the section where they are defined
   rather than copying it. For brevity, [HX.Y] is to be taken to refer
   to Section X.Y of the current HTTP/1.1 specification (RFC 2616 [26]).

   All the mechanisms specified in this document are described in both
   prose and an augmented Backus-Naur form (BNF) similar to that used in
   [H2.1]. It is described in detail in RFC 2234 [14], with the differ-
   ence that this RTSP specification maintains the "1#" "#" notation for
   comma-separated lists. lists from [H2.1].

   In this draft, we use indented and smaller-type paragraphs to provide
   background and motivation. This is intended to give readers who were
   not involved with the formulation of the specification an understand-
   ing
   understanding of why things are the way that they are in RTSP.

   b

3 Protocol Parameters

3.1 RTSP Version

   HTTP Specification Section [H3.1] applies, with HTTP replaced by
   RTSP. This specification defines version 1.0 of RTSP.

3.2 RTSP URL

   The "rtsp" and "rtspu" schemes are used to refer to network resources
   via the RTSP protocol. This section defines the scheme-specific syn-
   tax and semantics for RTSP URLs.                                      |

   rtsp_URL  =  ( "rtsp:" | / "rtspu:" / "rtsps" )                            ||
                "//" host [ ":" port ] [ abs_path ]                         ||
   host      =  <A legal Internet host domain name of IP address
                (in dotted decimal form), as  As defined by RFC 2732 [30]                                 ||
   abs_path  =  As defined by Section 2.1
                of RFC 1123 [15]> 2396 [22]                                 ||
   port      =  *DIGIT

   abs_path is defined in [H3.2.1].                                                      ||

     Note that fragment and query identifiers do not have a well-
     defined meaning at this time, with the interpretation left to
     the RTSP server.

   The scheme rtsp requires that commands are issued via a reliable pro-
   tocol (within the Internet, TCP), while the scheme rtspu identifies
   an unreliable protocol (within the Internet, UDP). The scheme rtsps
   identifies a reliable transport using TLS [27].

   If the port is empty or not given, port 554 is assumed.  The semantics seman-
   tics are that the identified resource can be controlled by RTSP at
   the server listening for TCP (scheme "rtsp") connections or UDP
   (scheme "rtspu") packets on that port of host, and the Request-URI
   for the resource is rtsp_URL.

   The use of IP addresses in URLs SHOULD be avoided whenever possible
   (see RFC 1924 [16]). Note: Using qualified domain names in any URL is
   one requirement for making it possible for RFC 2326 implementations
   of RTSP to use IPv6. This specification is updated to allow for lit-
   eral IPv6 addresses in RTSP URLs using the host specification in RFC
   2732 [30].

   A presentation or a stream is identified by a textual media identi-
   fier, using the character set and escape conventions [H3.2] of URLs
   (RFC 1738 [17]). 2396 [22]). URLs may refer to a stream or an aggregate of
   streams, i.e., a presentation. Accordingly, requests described in
   Section 10 can apply to either the whole presentation or an individ-
   ual stream within the presentation. Note that some request methods
   can only be applied to streams, not presentations and vice versa.

   For example, the RTSP URL:

     rtsp://media.example.com:554/twister/audiotrack

identifies the audio stream within the presentation "twister", which can
be controlled via RTSP requests issued over a TCP connection to port 554
of host media.example.com

   Also, the RTSP URL:

     rtsp://media.example.com:554/twister

identifies the presentation "twister", which may be composed of audio
and video streams.

     This does not imply a standard way to reference streams in
     URLs. The presentation description defines the hierarchical
     relationships in the presentation and the URLs for the indi-
     vidual streams. A presentation description may name a stream
     "a.mov" and the whole presentation "b.mov".

   The path components of the RTSP URL are opaque to the client and do
   not imply any particular file system structure for the server.

     This decoupling also allows presentation descriptions to be
     used with non-RTSP media control protocols simply by replacing
     the scheme in the URL.

3.3 Session Identifiers

   Session identifiers are opaque strings of arbitrary length. Linear
   white space must be URL-escaped. A session identifier MUST be chosen
   randomly and MUST be at least eight octets long to make guessing it
   more difficult. (See Section 16.) 17.)
   session-id  =  8*( ALPHA | / DIGIT | / safe )

3.4 SMPTE Relative Timestamps

   A SMPTE relative timestamp expresses time relative to the start of
   the clip. Relative timestamps are expressed as SMPTE time codes for
   frame-level access accuracy. The time code has the format
                  hours:minutes:seconds:frames.subframes,
   with the origin at the start of the clip. The default smpte format
   is"SMPTE 30 drop" format, with frame rate is 29.97 frames per second.
   Other SMPTE codes MAY be supported (such as "SMPTE 25") through the
   use of alternative use of "smpte time". For the "frames" field in the
   time value can assume the values 0 through 29. The difference between
   30 and 29.97 frames per second is handled by dropping the first two
   frame indices (values 00 and 01) of every minute, except every tenth
   minute. If the frame value is zero, it may be omitted. Subframes are
   measured in one-hundredth of a frame.

   smpte-range       =  smpte-type "=" smpte-range-spec                     ||
   smpte-range-spec  =  ( smpte-time "-" [ smpte-time ] ) |                   ||
                     /  ( "-" smpte-time )                                  ||
   smpte-type        =  "smpte" | / "smpte-30-drop" | / "smpte-25"              ||
                        ; other timecodes may be added                      ||
   smpte-time        =  1*2DIGIT ":" 1*2DIGIT ":" 1*2DIGIT                  ||
                        [ ":" 1*2DIGIT ] [ "." 1*2DIGIT ] ]                   ||

   Examples:

     smpte=10:12:33:20-
     smpte=10:07:33-
     smpte=10:07:00-10:07:33:05.01
     smpte-25=10:07:00-10:07:33:05.01

3.5 Normal Play Time

   Normal play time (NPT) indicates the stream absolute position rela-
   tive to the beginning of the presentation. presentation, not to be confused with
   the Network Time Protocol (NTP). The timestamp consists of a decimal
   fraction. The part left of the decimal may be expressed in either
   seconds or hours, minutes, and seconds. The part right of the decimal
   point measures fractions of a second.

   The beginning of a presentation corresponds to 0.0 seconds.  Negative
   values are not defined. The special constant now is defined as the
   current instant of a live event. It may MAY only be used only for live events. events,
   and SHALL NOT be used for on-demand content.

   NPT is defined as in DSM-CC: "Intuitively, NPT is the clock the
   viewer associates with a program. It is often digitally displayed on
   a VCR. NPT advances normally when in normal play mode (scale = 1),
   advances at a faster rate when in fast scan forward (high positive
   scale ratio), decrements when in scan reverse (high negative scale
   ratio) and is fixed in pause mode. NPT is (logically) equivalent to
   SMPTE time codes."  [5]

   npt-range       =  ["npt" "="] npt-range-spec
                      ; implementations SHOULD use npt= prefix, but SHOULD
                      ; be prepared to interoperate with RFC 2326
                      ; implementations which don't use it
   npt-range-spec  =  ( npt-time "-" [ npt-time ] ) | / ( "-" npt-time )
   npt-time        =  "now" | / npt-sec | / npt-hhmmss
   npt-sec         =  1*DIGIT [ "." *DIGIT ]
   npt-hhmmss      =  npt-hh ":" npt-mm ":" npt-ss [ "." *DIGIT ]
   npt-hh          =  1*DIGIT ; any positive number
   npt-mm          =  1*2DIGIT ; 0-59
   npt-ss          =  1*2DIGIT ; 0-59

   Examples:

     npt=123.45-125
     npt=12:05:35.3-
     npt=now-

     The syntax conforms to ISO 8601. The npt-sec notation is opti-
     mized for automatic generation, the ntp-hhmmss notation for
     consumption by human readers. The "now" constant allows
     clients to request to receive the live feed rather than the
     stored or time-delayed version. This is needed since neither
     absolute time nor zero time are appropriate for this case.

3.6 Absolute Time

   Absolute time is expressed as ISO 8601 timestamps, using UTC (GMT).
   Fractions of a second may be indicated.                               |
   utc-range       =  ["clock" "="]  "clock" "=" utc-range-spec                            ||
   utc-range-spec  =  ( utc-time "-" [ utc-time ] ) | / ( "-" utc-time )      ||
   utc-time        =  utc-date "T" utc-time "Z"                             ||
   utc-date        =  8DIGIT ; < YYYYMMDD >                                 ||
   utc-time        =  6DIGIT [ "." fraction ] ; < HHMMSS.fraction >         ||
   fraction        =  1*DIGIT                                               ||

   Example for November 8, 1996 at 14h37 and 20 and a quarter seconds
   UTC:

     19961108T143720.25Z

3.7 Option Tags

   Option tags are unique identifiers used to designate new options in
   RTSP. These tags are used in in Require (Section 12.32) and 12.32), Proxy-
   Require (Section 12.27) 12.27), and Supported (Section 12.38) header fields.

   Syntax:

   option-tag  =  token

   The creator of a new RTSP option should either prefix the option with
   a reverse domain name (e.g., "com.foo.mynewfeature" is an apt name
   for a feature whose inventor can be reached at "foo.com"), or regis-
   ter the new option with the Internet Assigned Numbers Authority
   (IANA).

3.7.1 Registering New Option Tags with
   (IANA), see IANA

   When registering a new RTSP option, the following information should
   be provided:

     + Name and description of option. The name may be of any length,
       but SHOULD be no more than twenty characters long. The name MUST
       not contain any spaces, control characters or periods.

     + Indication of who has change control over the option (for exam-
       ple, IETF, ISO, ITU-T, other international standardization bod-
       ies, a consortium or a particular company or group of companies);

     + A reference to a further description, if available, for example
       (in order of preference) an RFC, a published paper, a patent fil-
       ing, a technical report, documented source code or a computer
       manual;

     + For proprietary options, contact information (postal and email
       address); Section 18.

4 RTSP Message

   RTSP is a text-based protocol and uses the ISO 10646 character set in
   UTF-8 encoding (RFC 2279 [18]). Lines are terminated by CRLF, but
   receivers should be prepared to also interpret CR and LF by them-
   selves as line terminators.

     Text-based protocols make it easier to add optional parameters
     in a self-describing manner. Since the number of parameters
     and the frequency of commands is low, processing efficiency is
     not a concern. Text-based protocols, if done carefully, also
     allow easy implementation of research prototypes in scripting
     languages such as Tcl, Visual Basic and Perl.

   The 10646 character set avoids tricky character set switching, but is
   invisible to the application as long as US-ASCII is being used.  This
   is also the encoding used for RTCP. ISO 8859-1 translates directly
   into Unicode with a high-order octet of zero. ISO 8859-1 characters
   with the most-significant bit set are represented as 1100001x
   10xxxxxx. (See RFC 2279 [18])

   RTSP messages can be carried over any lower-layer transport protocol  |
   that is 8-bit clean. RTSP messages are vulnerable to bit errors and   |
   SHOULD NOT be subjected to them.

   Requests contain methods, the object the method is operating upon and
   parameters to further describe the method. Methods are idempotent,
   unless otherwise noted. Methods are also designed to require little
   or no state maintenance at the media server.

4.1 Message Types

   See [H4.1] [H4.1].

4.2 Message Headers

   See [H4.2] [H4.2].

4.3 Message Body

   See [H4.3]

4.4 Message Length

   When a message body is included with a message, the length of that
   body is determined by one of the following (in order of precedence):

     1.   Any response message which MUST NOT include a message body
          (such as the 1xx, 204, and 304 responses) is always terminated
          by the first empty line after the header fields, regardless of
          the entity-header fields present in the message. (Note: An
          empty line consists of only CRLF.)

     2.   If a Content-Length header field (section 12.14) is present,
          its value in bytes represents the length of the message-body.
          If this header field is not present, a value of zero is
          assumed.

   Note that RTSP does not (at present) support the HTTP/1.1 "chunked"
   transfer coding(see [H3.6.1]) and requires the presence of the Con-
   tent-Length header field.

     Given the moderate length of presentation descriptions
     returned, the server should always be able to determine its
     length, even if it is generated dynamically, making the chun-
     ked transfer encoding unnecessary.

5 General Header Fields

   See [H4.5], except that Pragma, Trailer, Transfer-Encoding, Upgrade,
   and Warning headers are not defined: defined. RTSP further defines the CSeq,
   and Timestamp:

   general-header  =  Cache-Control  ; Section 12.9
                   |
                   /  Connection     ; Section 12.10
                   |
                   /  CSeq           ; Section 12.17
                   |
                   /  Date           ; Section 12.18
                   |
                   /  Timestamp      ; Section 12.39
                   /  Via            ; Section 12.44

6 Request

   A request message from a client to a server or vice versa includes,
   within the first line of that message, the method to be applied to
   the resource, the identifier of the resource, and the protocol ver-
   sion in use.

   Request  =   Request-Line      ; Section 6.1
            *(  general-header    ; Section 5
            |
            /   request-header    ; Section 6.2
            |
            /   entity-header )   ; Section 8.1
                CRLF
                [ message-body ]  ; Section 4.3

6.1 Request Line

   Request-Line  =  Method SP Request-URI SP RTSP-Version CRLF

   Method  =  "DESCRIBE"        ; Section 10.2
           |
           /  "ANNOUNCE"        ; Section 10.3
           |
           /  "GET_PARAMETER"   ; Section 10.8
           |
           /  "OPTIONS"         ; Section 10.1
           |
           /  "PAUSE"           ; Section 10.6
           |
           /  "PLAY"            ; Section 10.5
           |
           /  "PING"            ; Section 10.12
           /  "RECORD"          ; Section 10.11
           |
           /  "REDIRECT"        ; Section 10.10
           |
           /  "SETUP"           ; Section 10.4
           |
           /  "SET_PARAMETER"   ; Section 10.9
           |
           /  "TEARDOWN"        ; Section 10.7
           |
           /  extension-method

   extension-method  =  token
   Request-URI       =  "*" | / absolute_URI
   RTSP-Version      =  "RTSP" "/" 1*DIGIT "." 1*DIGIT

6.2 Request Header Fields

   request-header  =  Accept             ; Section 12.1
                   |
                   /  Accept-Encoding    ; Section 12.2
                   |
                   /  Accept-Language    ; Section 12.3
                   |
                   /  Authorization      ; Section 12.6
                   |
                   /  Bandwidth          ; Section 12.7
                   |
                   /  Blocksize          ; Section 12.8
                   |
                   /  From               ; Section 12.20
                   |
                   /  If-Modified-Since  ; Section 12.23
                   |
                   /  Proxy-Require      ; Section 12.27
                   |
                   /  Range              ; Section 12.29
                   |
                   /  Referer            ; Section 12.30
                   |
                   /  Require            ; Section 12.32
                   |
                   /  Scale              ; Section 12.34
                   |
                   /  Session            ; Section 12.37
                   |
                   /  Speed              ; Section 12.35
                   |
                   /  Supported          ; Section 12.38
                   /  Transport          ; Section 12.40
                   |
                   /  User-Agent         ; Section 12.42

   Note that in contrast to HTTP/1.1 [26], RTSP requests always contain
   the absolute URL (that is, including the scheme, host and port)
   rather than just the absolute path.

     HTTP/1.1 requires servers to understand the absolute URL, but
     clients are supposed to use the Host request header. This is
     purely needed for backward-compatibility with HTTP/1.0
     servers, a consideration that does not apply to RTSP.

   The asterisk "*" in the Request-URI means that the request does not
   apply to a particular resource, but to the server or proxy itself,
   and is only allowed when the method used does not necessarily apply
   to a resource.

   One example would be:

     OPTIONS * RTSP/1.0

Which will determine the capabilities of the server or the proxy that
first receives the request. If one needs to address the server explic-
itly one needs to put in a absolute URL with the servers address.

     OPTIONS rtsp://example.com RTSP/1.0

7 Response

   [H6] applies except that HTTP-Version is replaced by RTSP-Version.
   Also, RTSP defines additional status codes and does not define some
   HTTP codes. The valid response codes and the methods they can be used
   with are defined in Table 1.

   After receiving and interpreting a request message, the recipient
   responds with an RTSP response message.

   Response  =   Status-Line       ; Section 7.1
             *(  general-header    ; Section 5
             |
             /   response-header   ; Section 7.1.2
             |
             /   entity-header )   ; Section 8.1
                 CRLF
                 [ message-body ]  ; Section 4.3

7.1 Status-Line

   The first line of a Response message is the Status-Line, consisting
   of the protocol version followed by a numeric status code, and the
   textual phrase associated with the status code, with each element
   separated by SP characters. No CR or LF is allowed except in the
   final CRLF sequence.

   Status-Line  =  RTSP-Version SP Status-Code SP Reason-Phrase CRLF

7.1.1 Status Code and Reason Phrase

   The Status-Code element is a 3-digit integer result code of the
   attempt to understand and satisfy the request. These codes are fully
   defined in Section 11. The Reason-Phrase is intended to give a short
   textual description of the Status-Code. The Status-Code is intended
   for use by automata and the Reason-Phrase is intended for the human
   user. The client is not required to examine or display the Reason-
   Phrase.

   The first digit of the Status-Code defines the class of response. The
   last two digits do not have any categorization role.  There are 5
   values for the first digit:

     + 1xx: Informational - Request received, continuing process

     + 2xx: Success - The action was successfully received, understood,
       and accepted

     + 3xx: Redirection - Further action must be taken in order to com-
       plete the request

     + 4xx: Client Error - The request contains bad syntax or cannot be
       fulfilled

     + 5xx: Server Error - The server failed to fulfill an apparently
       valid request

   The individual values of the numeric status codes defined for
   RTSP/1.0, and an example set of corresponding Reason-Phrase's, are
   presented below. The reason phrases listed here are only recommended
   -- they may be replaced by local equivalents without affecting the
   protocol. Note that RTSP adopts most HTTP/1.1 [26] status codes and
   adds RTSP-specific status codes starting at x50 to avoid conflicts
   with newly defined HTTP status codes.

     Status-Code  =  "100"          ; Continue
                  |
                  /  "200"          ; OK
                  |
                  /  "201"          ; Created
                  |
                  /  "250"          ; Low on Storage Space
                  |
                  /  "300"          ; Multiple Choices
                  |
                  /  "301"          ; Moved Permanently
                  |
                  /  "302"          ; Moved Temporarily
                  |
                  /  "303"          ; See Other
                  |
                  /  "304"          ; Not Modified
                  |
                  /  "305"          ; Use Proxy
                  |
                  /  "350"          ; Going Away
                  /  "351"          ; Load Balancing
                  /  "400"          ; Bad Request
                  |
                  /  "401"          ; Unauthorized
                  |
                  /  "402"          ; Payment Required
                  |
                  /  "403"          ; Forbidden
                  |
                  /  "404"          ; Not Found
                  |
                  /  "405"          ; Method Not Allowed
                  |
                  /  "406"          ; Not Acceptable
                  |
                  /  "407"          ; Proxy Authentication Required
                  |
                  /  "408"          ; Request Time-out
                  |
                  /  "410"          ; Gone
                  |
                  /  "411"          ; Length Required
                  |
                  /  "412"          ; Precondition Failed
                  |
                  /  "413"          ; Request Entity Too Large
                  |
                  /  "414"          ; Request-URI Too Large
                  |
                  /  "415"          ; Unsupported Media Type
                  |
                  /  "451"          ; Parameter Not Understood
                  |
                  /  "452"          ; reserved
                  |
                  /  "453"          ; Not Enough Bandwidth
                  |
                  /  "454"          ; Session Not Found
                  |
                  /  "455"          ; Method Not Valid in This State
                  |
                  /  "456"          ; Header Field Not Valid for Resource
                  |
                  /  "457"          ; Invalid Range
                  |
                  /  "458"          ; Parameter Is Read-Only
                  |
                  /  "459"          ; Aggregate operation not allowed
                  |
                  /  "460"          ; Only aggregate operation allowed
                  |
                  /  "461"          ; Unsupported transport
                  |
                  /  "462"          ; Destination unreachable
                  |
                  /  "500"          ; Internal Server Error
                  |
                  /  "501"          ; Not Implemented
                  |
                  /  "502"          ; Bad Gateway
                  |
                  /  "503"          ; Service Unavailable
                  |
                  /  "504"          ; Gateway Time-out
                  |
                  /  "505"          ; RTSP Version not supported
                  |
                  /  "551"          ; Option not supported
                  |
                  /  extension-code

     extension-code  =  3DIGIT
     Reason-Phrase   =  *<TEXT, excluding CR, LF>
   RTSP status codes are extensible. RTSP applications are not required
   to understand the meaning of all registered status codes, though such
   understanding is obviously desirable. However, applications MUST
   understand the class of any status code, as indicated by the first
   digit, and treat any unrecognized response as being equivalent to the
   x00 status code of that class, with the exception that an unrecog-
   nized response MUST NOT be cached. For example, if an unrecognized
   status code of 431 is received by the client, it can safely assume
   that there was something wrong with its request and treat the
   response as if it had received a 400 status code. In such cases, user
   agents SHOULD present to the user the entity returned with the
   response, since that entity is likely to include human-readable
   information which will explain the unusual status.

7.1.2 Response Header Fields

   The response-header fields allow the request recipient to pass addi-
   tional information about the response which cannot be placed in the
   Status-Line. These header fields give information about the server
   and about further access to the resource identified by the Request-
   URI.

   response-header  =  Accept-Ranges       ; Section
   12.4
                    /  Location            ; Section 12.25
                    |
                    /  Proxy-Authenticate  ; Section 12.26
                    |
                    /  Public              ; Section 12.28
                    |
                    /  Range               ; Section 12.29
                    |
                    /  Retry-After         ; Section 12.31
                    |
                    /  RTP-Info            ; Section 12.33
                    |
                    /  Scale               ; Section 12.34
                    |
                    /  Session             ; Section 12.37
                    |
                    /  Server              ; Section 12.36
                    |
                    /  Speed               ; Section 12.35
                    |
                    /  Transport           ; Section 12.40
                    |
                    /  Unsupported         ; Section 12.41
                    |
                    /  Vary                ; Section 12.43
                    |
                    /  WWW-Authenticate    ; Section 12.45

   Response-header field names can be extended reliably only in combina-
   tion with a change in the protocol version. However, new or experi-
   mental header fields MAY be given the semantics of response-header
   fields if all parties in the communication recognize them to be
   response-header fields. Unrecognized header fields are treated as
   entity-header fields.

        Code  reason
        --------------------------------------------------------
        100   Continue                          all
        --------------------------------------------------------
        200   OK                                all
        201   Created                           RECORD
        250   Low on Storage Space              RECORD
        --------------------------------------------------------
        300   Multiple Choices                  all
        301   Moved Permanently                 all
        302   Moved Temporarily   Found                             all
        303   See Other                         all
        305   Use Proxy                         all
        350   Going Away                        all
        351   Load Balancing                    all
        --------------------------------------------------------
        400   Bad Request                       all
        401   Unauthorized                      all
        402   Payment Required                  all
        403   Forbidden                         all
        404   Not Found                         all
        405   Method Not Allowed                all
        406   Not Acceptable                    all
        407   Proxy Authentication Required     all
        408   Request Timeout                   all
        410   Gone                              all
        411   Length Required                   all
        412   Precondition Failed               DESCRIBE, SETUP
        413   Request Entity Too Large          all
        414   Request-URI Too Long              all
        415   Unsupported Media Type            all
        451   Parameter Not Understood          SETUP          SET_PARAMETER
        452   reserved                          n/a
        453   Not Enough Bandwidth              SETUP
        454   Session Not Found                 all
        455   Method Not Valid In This State    all
        456   Header Field Not Valid            all
        457   Invalid Range                     PLAY                     PLAY, PAUSE
        458   Parameter Is Read-Only            SET_PARAMETER
        459   Aggregate Operation Not Allowed   all
        460   Only Aggregate Operation Allowed  all
        461   Unsupported Transport             all
        462   Destination Unreachable           all
        --------------------------------------------------------
        500   Internal Server Error             all
        501   Not Implemented                   all
        502   Bad Gateway                       all
        503   Service Unavailable               all
        504   Gateway Timeout                   all
        505   RTSP Version Not Supported        all
        551   Option not support                all

   Table 1: Status codes and their usage with RTSP methods

   entity-header fields.

8 Entity

   Request and Response messages MAY transfer an entity if not otherwise
   restricted by the request method or response status code. An entity
   consists of entity-header fields and an entity-body, although some
   responses will only include the entity-headers.

   In this section, both sender and recipient refer to either the client
   or the server, depending on who sends and who receives the entity.

8.1 Entity Header Fields

   Entity-header fields define optional metainformation meta-information about the
   entity-body or, if no body is present, about the resource identified
   by the request.

   entity-header     =  Allow             ; Section 12.5
                     |
                     /  Content-Base      ; Section 12.11
                     |
                     /  Content-Encoding  ; Section 12.12
                     |
                     /  Content-Language  ; Section 12.13
                     |
                     /  Content-Length    ; Section 12.14
                     |
                     /  Content-Location  ; Section 12.15
                     |
                     /  Content-Type      ; Section 12.16
                     |
                     /  Expires           ; Section 12.19
                     |
                     /  Last-Modified     ; Section 12.24
                     |
                     /  extension-header
   extension-header  =  message-header

   The extension-header mechanism allows additional entity-header fields
   to be defined without changing the protocol, but these fields cannot
   be assumed to be recognizable by the recipient. Unrecognized header
   fields SHOULD be ignored by the recipient and forwarded by proxies.

8.2 Entity Body

   See [H7.2] with the addition that a RTSP message with an entity body  |
   MUST include a Content-Type header.

9 Connections

   RTSP requests can be transmitted in several different ways:

     + persistent transport connections used for several request-
       response transactions;

     + one connection per request/response transaction;

     + connectionless mode.

   The type of transport connection is defined by the RTSP URI (Section
   3.2). For the scheme "rtsp", a persistent connection is assumed, while the
   scheme "rtspu" calls for RTSP requests to be sent without setting up
   a connection.

   Unlike HTTP, RTSP allows the media server to send requests to the
   media client. However, this is only supported for persistent connec-
   tions, as the media server otherwise has no reliable way of reaching
   the client.  Also, this is the only way that requests from media
   server to client are likely to traverse firewalls.

9.1 Pipelining

   A client that supports persistent connections or connectionless mode
   MAY "pipeline" its requests (i.e., send multiple requests without
   waiting for each response). A server MUST send its responses to those
   requests in the same order that the requests were received.

9.2 Reliability and Acknowledgements

   Requests are acknowledged by the receiver unless they are sent to a   |
   multicast group. If there is no acknowledgement, the sender may       |
   resend the same message after a timeout of one round-trip time (RTT). |
   The round-trip time is estimated as in TCP (RFC 1123) [15], with an   |
   initial round-trip value of 500 ms. An implementation MAY cache the   |
   last RTT measurement as the initial value for future connections.     |

   If a reliable transport protocol is used to carry RTSP, requests MUST |
   NOT be retransmitted; the RTSP application MUST instead rely on the   |
   underlying transport to provide reliability.                          |

     If both the underlying reliable transport such as TCP and the  |
     RTSP application retransmit requests, it is possible that each |
     packet loss results in two retransmissions. The receiver can-  |
     not typically take advantage of the application-layer retrans- |
     mission since the transport stack will not deliver the         |
     application-layer retransmission before the first attempt has  |
     reached the receiver. If the packet loss is caused by conges-  |
     tion, multiple retransmissions at different layers will exac-  |
     erbate the congestion.                                         |

   If RTSP is used over a small-RTT LAN, standard procedures for opti-   |
   mizing initial TCP round trip estimates, such as those used in T/TCP  |
   (RFC 1644) [19], can be beneficial.                                   |

   The Timestamp header (Section 12.39) is used to avoid the retransmis- |
   sion ambiguity problem [20] and obviates the need for Karn's algo-    |
   rithm.                                                                |

   Each request carries a sequence number in the CSeq header (Section    |
   12.17), which is MUST be incremented by one for each distinct request trans-
   mitted.    |
   transmitted. If a request is repeated because of lack of acknowledgement, acknowledge- |
   ment, the request MUST carry the original sequence number (i.e., the  |
   sequence number is not incremented).                                  |

   Systems implementing RTSP MUST support carrying RTSP over TCP and MAY |
   support UDP. The default port for the RTSP server is 554 for both UDP |
   and TCP.                                                              |

   A number of RTSP packets destined for the same control end point may  |
   be packed into a single lower-layer PDU or encapsulated into a TCP    |
   stream.  RTSP data MAY be interleaved with RTP and RTCP packets.      |
   Unlike HTTP, an RTSP message MUST contain a Content-Length header     |
   field whenever that message contains a payload. Otherwise, an RTSP    |
   packet is terminated with an empty line immediately following the     |
   last message header.

10 Method Definitions                                                  |

9.3 The method token indicates the method to usage of connections                                             |

   TCP can be performed used for both persistent connections and for one message   |
   exchange per connection, as presented above. This section gives fur-  |
   ther rules and recommendations on how to handle these connections so  |
   maximum interoperability and flexibility can be achieved.             |

   A server SHALL handle both persistent connections and one             |
   request/response transaction per connection. A persistent connection  |
   MAY be used for all transactions between the resource
   identified by server and client,       |
   including messages to multiple RTSP sessions. However the Request-URI case-sensitive. New methods may persistent  |
   connection MAY also be
   defined closed after a few message exchanges, e.g. the |
   initial setup and play command in a session. Later when the future. Method names may not start with client    |
   wishes to send a $ character
   (decimal 24) and must be new request, e.g.  pause, to the session a token. Methods are summarized in Table 2.

   Notes new con-  |
   nection is opened. This connection may either be for a single message |
   exchange or can be kept open for several messages, i.e. persistent.   |
   The client MAY close the connection at any time when no outstanding   |
   request/response transactions exist. The server SHOULD NOT close the  |
   connection unless at least one RTSP session timeout period has passed |
   without data traffic. A server MUST NOT close a connection directly   |
   after responding to a TEARDOWN request for the whole session.         |

   The client SHOULD NOT have more than one connection to the server at  |
   any given point. If a client or proxy handles multiple RTSP sessions  |
   on Table 2: PAUSE the same server, it is recommended, but not required RECOMMENDED to use only a single connec-    |
   tion.                                                                 |

   Older services which was implemented according to RFC 2326 sometimes  |
   requires the client to use persistent connection. The client closing  |
   the connection may result in that the server removes the session. To  |
   achieve interoperability with old servers any client is strongly REC- |
   OMMENDED to use persistent connections. To make it practically possi- |
   ble for a
   fully functional client to the rules outlined in this chapter a feature tag  |
   is defined.                                                           |

   con.non-persistent                                                       ||

   If a service requires the use of persistent connection a option tag   |
   is specified for usage in Require and Proxy-Require.                  |

   con.persistent                                                           ||

   A server implemented according to this specification MUST respond     |
   that it supports the feature tag above. A client MAY send a request   |
   including the Supported header in a request to determine support of   |
   non-persistent connections. A server supporting non-persistent con-   |
   nections MUST return the "con.non-persistent" feature tag in its      |
   response. If the client receives the feature tag in the response, it  |
   can be built certain that does the server handles non-persistent connections.    |

9.4 Use of Transport Layer Security                                      |

9.5 Use of IPv6                                                          |

   This specification has been updated so that it supports IPv6.  How-   |
   ever this support was not present in RFC 2326 therefore some interop- |
   erability issues exist. A RFC 2326 implementation can support this
   method, for example, for live feeds. If IPv6 as |
   long as no explicit IPv6 addresses are used within RTSP messages.     |
   This require that any RTSP URL pointing at a server does IPv6 host must use fully |
   qualified domain name and not support a
   particular method, it IPv6 address.  Further the Transport  |
   header must not use the parameters source and destination.            |

   Implementations according to this specification MUST return 501 (Not Implemented) understand IPv6  |
   addresses in URLs, and headers. By this requirement the option-tag    |
   "play.basic" and "record.basic" can be used to determine that a       |
   server or client
   SHOULD not try this is capable of handling IPv6 within RTSP.             |

10 Method Definitions

   The method again for this server.

10.1 OPTIONS token indicates the method to be performed on the resource |
   identified by the Request-URI case-sensitive. New methods may be      |
   defined in the future. Method names may not start with a $ character  |
   (decimal 24) and must be a token as defined by the ABNF. Methods are  |
   summarized in Table 2.                                                |

    method         direction   object  requirement
      -------------------------------------------------------------  Server req.    Client req.
    ----------------------------------------------------------------
    DESCRIBE       C->S        P,S     recommended    recommended
    ANNOUNCE       C->S, S->C  P,S     optional       optional
    GET_PARAMETER  C->S, S->C  P,S     optional       optional
    OPTIONS        C->S, S->C  P,S     required (S->C: optional)     R=Req, Sd=Opt  Sd=Req, R=Opt
    PAUSE          C->S        P,S     recommended    recommended
    PING           C->S, S->C  P,S     recommended    optional
    PLAY           C->S        P,S     required       required
    RECORD         C->S        P,S     optional       optional
    REDIRECT       S->C        P,S     optional       optional
    SETUP          C->S        S       required       required
    SET_PARAMETER  C->S, S->C  P,S     optional       optional
    TEARDOWN       C->S        P,S     required       required

   Table  2: Overview of RTSP methods, their direction, and what objects
   (P: presentation, S: stream) they operate on. Legend: R=Responde  to,
   Sd=Send, Opt: Optional, Req: Required, Rec: Recommended

   Notes on

   The behavior Table 2: PAUSE is recommended, but not required in that a
   fully functional server can be built that does not support this
   method, for example, for live feeds. If a server does not support a
   particular method, it MUST return 501 (Not Implemented) and a client
   SHOULD not try this method again for this server.

10.1 OPTIONS
   The behavior is equivalent to that described in [H9.2]. An OPTIONS    |
   request may be issued at any time, e.g., if the client is about to    |
   try a nonstandard request. It does not influence server the session state.   |
   The Public header MUST be included in responses to indicate which     |
   methods that are supported by the server. To specify which methods    |
   that are possible to use for the specified resource, the Allow MAY be |
   used. By including in the OPTIONS request a Supported header, the     |
   requester can determine which options the other part supports.        |

   The request URI determines which scope the options request has. By    |
   giving the URI of a certain media the capabilities regarding this     |
   media will be responded. By using the "*" URI the request regards the |
   server without any media relevance.

   Example:

     C->S:  OPTIONS * RTSP/1.0
            CSeq: 1
            User-Agent: PhonyClient 1.2
            Require: implicit-play
            Proxy-Require: gzipped-messages
            Supported: play-basic

     S->C:  RTSP/1.0 200 OK
            CSeq: 1
            Public: DESCRIBE, SETUP, TEARDOWN, PLAY, PAUSE
            Supported: play-basic, gzipped-messages, implicit-play
            Server: PhonyServer 1.0

   Note that these the option tags in Require and Proxy-Require are necessarily necessar-
   ily fictional features (one would hope that we would not purposefully
   overlook a truly useful feature just so that we could have a strong
   example in this section).

10.2 DESCRIBE

   The DESCRIBE method retrieves the description of a presentation or
   media object identified by the request URL from a server. It may use
   the Accept header to specify the description formats that the client
   understands. The server responds with a description of the requested
   resource. The DESCRIBE reply-response pair constitutes the media ini-
   tialization phase of RTSP.

   Example:

     C->S: DESCRIBE rtsp://server.example.com/fizzle/foo RTSP/1.0
           CSeq: 312
           User-Agent: PhonyClient 1.2
           Accept: application/sdp, application/rtsl, application/mheg

     S->C: RTSP/1.0 200 OK
           CSeq: 312
           Date: 23 Jan 1997 15:35:06 GMT
           Server: PhonyServer 1.0
           Content-Type: application/sdp
           Content-Length: 376

           v=0
           o=mhandley 2890844526 2890842807 IN IP4 126.16.64.4
           s=SDP Seminar
           i=A Seminar on the session description protocol
           u=http://www.cs.ucl.ac.uk/staff/M.Handley/sdp.03.ps
           e=mjh@isi.edu (Mark Handley)
           c=IN IP4 224.2.17.12/127
           t=2873397496 2873404696
           a=recvonly
           m=audio 3456 RTP/AVP 0
           m=video 2232 RTP/AVP 31
           m=whiteboard
           m=application 32416 UDP WB
           a=orient:portrait

   The DESCRIBE response MUST contain all media initialization informa-
   tion for the resource(s) that it describes. If a media client obtains
   a presentation description from a source other than DESCRIBE and that
   description contains a complete set of media initialization parame-
   ters, the client SHOULD use those parameters and not then request a
   description for the same media via RTSP.

   Additionally, servers SHOULD NOT use the DESCRIBE response as a means
   of media indirection.

     By forcing a DESCRIBE response to contain all media initial-
     ization for the set of streams that it describes, and discour-
     aging use of DESCRIBE for media indirection, we avoid looping
     problems that might result from other approaches.

   Media initialization is a requirement for any RTSP-based system, but
   the RTSP specification does not dictate that this must be done via
   the DESCRIBE method. There are three ways that an RTSP client may
   receive initialization information:

     + via RTSP's DESCRIBE method;

     + via some other protocol (HTTP, email attachment, etc.);

     + via the command line or standard input (thus working as a browser
       helper application launched with an SDP file or other media ini-
       tialization format).

   It is RECOMMENDED that minimal servers support the DESCRIBE method,
   and highly recommended that minimal clients support the ability to
   act as a "helper application" that accepts a media initialization
   file from standard input, command line, and/or other means that are
   appropriate to the operating environment of the client.

10.3 ANNOUNCE

   The ANNOUNCE method serves two purposes:

   When sent from client to server, ANNOUNCE posts the description of a
   presentation or media object identified by the request URL to a
   server.  When sent from server to client, ANNOUNCE updates the ses-
   sion description in real-time.

   If a new media stream is added to a presentation (e.g., during a live
   presentation), the whole presentation description should be sent
   again, rather than just the additional components, so that components
   can be deleted.

   Example:

     C->S: ANNOUNCE rtsp://server.example.com/fizzle/foo RTSP/1.0
           CSeq: 312
           Date: 23 Jan 1997 15:35:06 GMT
           Session: 47112344
           Content-Type: application/sdp
           Content-Length: 332

           v=0
           o=mhandley 2890844526 2890845468 IN IP4 126.16.64.4
           s=SDP Seminar
           i=A Seminar on the session description protocol
           u=http://www.cs.ucl.ac.uk/staff/M.Handley/sdp.03.ps
           e=mjh@isi.edu (Mark Handley)
           c=IN IP4 224.2.17.12/127
           t=2873397496 2873404696
           a=recvonly
           m=audio 3456 RTP/AVP 0
           m=video 2232 RTP/AVP 31

     S->C: RTSP/1.0 200 OK
           CSeq: 312
           Date: 23 Jan 1997 15:35:06 GMT
           Server: PhonyServer 1.0

10.4 SETUP

   The SETUP request for a URI specifies the transport mechanism to be
   used for the streamed media. A client can issue a SETUP request for a
   stream that is already set up or playing in the session to change
   transport parameters, which a server MAY allow. If it does not allow
   this, it MUST respond with error 455 (Method Not Valid In This
   State).

   A server MAY allow a client to do SETUP while in playing state to add |
   additional media streams. If not supported the server shall responde  |
   with error 455 (Method Not Allowed In This State). If supported the   |
   added media shall then start to play in sync with the already playing |
   media. To be able to sync the media with the already playing streams  |
   the SETUP response MUST include a RTP-Info header with the timestamp  |
   value, and a Range header with the corresponding normal play time. To |
   indicate support for this optional support the options-tag:           |
   "setup.playing" is defined.

   For the benefit of any intervening firewalls, a client must indicate
   the transport parame-
   ters parameters even if it has no influence over these
   parameters, for example, where the server advertises a fixed multicast multi-
   cast address.

     Since SETUP includes all transport initialization information,
     firewalls and other intermediate network devices (which need
     this information) are spared the more arduous task of parsing
     the DESCRIBE response, which has been reserved for media ini-
     tialization.

   The Transport header specifies the transport parameters acceptable to
   the client for data transmission; the response will contain the
   transport parameters selected by the server.

     C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0
           CSeq: 302
           Transport: RTP/AVP;unicast;client_port=4588-4589

     S->C: RTSP/1.0 200 OK
           CSeq: 302
           Date: 23 Jan 1997 15:35:06 GMT
           Server: PhonyServer 1.0
           Session: 47112344
           Transport: RTP/AVP;unicast;
             client_port=4588-4589;server_port=6256-6257

   The server generates session identifiers in response to SETUP
   requests. If a SETUP request to a server includes a session identi-
   fier, the server MUST bundle this setup request into the existing
   session (aggregated session) or return error 459 (Aggregate Operation
   Not Allowed) (see Section 11.4.10). 11.4.11).

   To control an aggregated session an aggregated control URI MUST be    |
   used. The aggregated control URI MUST be different from any of the    |
   media control URIs included in the aggregate. The aggregated URI      |
   SHOULD be specified by session description, as no general rule exist  |
   to derive it from the included media's.                               |

   A session will exist until it is torn down by a TEARDOWN request or   |
   times out. The server MAY remove a session that have had no liveness  |
   signs from the client in the specified timeout time. The default      |
   timeout time is 60 seconds, the server MAY set this to another value, |
   by in the SETUP response include a timeout value in the session       |
   header. For further discussion see chapter  12.37. Signs of client    |
   liveness are:                                                         |

     + RTCP sender or receiver reports from the client in any of the RTP |
       sessions part of the RTSP session.                                |

     + Any RTSP request which includes a Session header with the ses-    |
       sion's ID.                                                        |

10.5 PLAY

   The PLAY method tells the server to start sending data via the mecha-
   nism specified in SETUP. A client MUST NOT issue a PLAY request until
   any outstanding SETUP requests have been acknowledged as successful.

   The

   In an aggregated session the PLAY request positions the normal play time to the beginning of
   the range specified and delivers stream data until MUST contain an aggregated  |
   control URL. A server SHALL responde with error 460 (Only Aggregate   |
   Operation Allowed) if the end client PLAY request URI is for one of the
   range is reached. PLAY requests may be pipelined (queued); a server
   MUST queue PLAY requests to   |
   media. The media in an aggregate SHALL be executed played in order. That is, a PLAY
   request arriving while sync. If a previous client |
   want individual control of the media it must use separate RTSP ses-   |
   sions for each media.                                                 |

   The PLAY request is still active is
   delayed positions the normal play time to the beginning of   |
   the range specified by the Range header and delivers stream data      |
   until the first has been completed.

     This allows end of the range is reached. To allow for precise editing.  For example, regardless composi-  |
   tion multiple ranges MAY be specified.  The range values are valid if |
   all given ranges are part of any media. If a given range value points |
   outside of how
     closely spaced the two PLAY requests in media, the example below
     arrive, response SHALL be the server 457 (Invalid Range)   |
   error code.                                                           |

   The below example will first play seconds 10 through 15, then, immediately imme-  |
   diately following, seconds 20 to 25, and finally seconds 30 through   |
   the end.                                                              |

     C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0                  |
           CSeq: 835                                                     |
           Session: 12345678                                             |
           Range: npt=10-15

     C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0
           CSeq: 836
           Session: 12345678
           Range: npt=20-25

     C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0
           CSeq: 837
           Session: 12345678
           Range: npt=10-15, npt=20-25, npt=30-                          |

   See the description of the PAUSE request for further examples.

   A PLAY request without a Range header is legal. It starts playing a
   stream from the beginning unless the stream has been paused. If a
   stream has been paused via PAUSE, stream delivery resumes at the
   pause point.

   The Range header may also contain a time parameter. This parameter    |
   specifies a time in UTC at which the playback should start. If the    |
   message is received after the specified time, playback is started     |
   immediately. The time parameter may be used to aid in synchronization |
   of streams obtained from different sources. Note: The usage of time   |
   has two problems. First, at the time requested the RTSP state machine |
   may not accept the request. The client will not get any notification  |
   of the failure. Secondly, the server has difficulties to produce the  |
   synchronization information for the RTP-Info header ahead of the      |
   actually play-out. Due to these reasons it is RECOMMENDED that a      |
   client not issues more than one timed request and no request without  |
   timing , until it is performed. The server SHALL in responses to      |
   timed PLAY request give in the RTP-Info header, the sequence number   |
   of the next RTP packet that will be send for that media, the RTP      |
   timestamp value corresponding to the activation time of the request.  |
   Unless the session is in paused state and not plays a single media    |
   packet the RTP sequence number will be in error. The RTP timestamp    |
   should be correct unless another timestamp rate has been used in      |
   between the issuing of the request and activation.                    |

   For a on-demand stream, the server replies MUST reply with the actual range   |
   that will be played back. This may differ from the requested range if |
   alignment of the requested range to valid frame boundaries is         |
   required for the media source. If no range is specified in the        |
   request, the current start position is SHALL still be returned in the reply. The |
   unit of the range in the reply is the same as that in the request. If |
   the medias part of an aggregate has different lengths the PLAY        |
   request and any Range SHALL be performed as long it is valid for the  |
   longest media.  Media will be sent whenever it is available for the   |
   given play-out point.                                                 |

   After playing the desired range, the presentation is automatically NOT automati-    |
   cally paused, as if a media deliver simple stops. A PAUSE request had been MUST be     |
   issued before another PLAY request can issued. Note: This is one      |
   change resulting in a non-operability with RFC 2326 implementations.  |
   A client not issuing a PAUSE request before a new PLAY will be stuck  |
   in PLAYING state. A client desiring to play the media from the begin- |
   ning MUST send a PLAY request with a Range header pointing at the     |
   beginning, e.g. npt=0-.                                               |

   The following example plays the whole presentation starting at SMPTE
   time code 0:10:20 until the end of the clip. The playback is to start
   at 15:36 on 23 Jan 1997. Note: The RTP-Info headers has been broken
   into several lines to fit the page.

   C->S: PLAY rtsp://audio.example.com/twister.en RTSP/1.0
         CSeq: 833
         Session: 12345678
         Range: smpte=0:10:20-;time=19970123T153600Z

   S->C: RTSP/1.0 200 OK
         CSeq: 833
         Date: 23 Jan 1997 15:35:06 GMT
         Server: PhonyServer 1.0
         Range: smpte=0:10:22-;time=19970123T153600Z
           RTP-Info:url=rtsp://audio.example.com/twister.en;seq=14783;rtptime=2345962545
         RTP-Info:url=rtsp://example.com/twister.en;
            seq=14783;rtptime=2345962545
   For playing back a recording of a live presentation, it may be desir-
   able to use clock units:

     C->S: PLAY rtsp://audio.example.com/meeting.en RTSP/1.0
           CSeq: 835
           Session: 12345678
           Range: clock=19961108T142300Z-19961108T143520Z

     S->C: RTSP/1.0 200 OK
           CSeq: 835
           Date: 23 Jan 1997 15:35:06 GMT
           Server:PhonyServer 1.0
           Range: clock=19961108T142300Z-19961108T143520Z
           RTP-Info:url=rtsp://audio.example.com/meeting.en;seq=53745;rtptime=484589019
           RTP-Info:url=rtsp://example.com/meeting.en;
              seq=53745;rtptime=484589019

   A media server only supporting playback MUST support the npt format
   and MAY support the clock and smpte formats.

   All range specifiers in this specification allow for ranges with      |
   unspecified begin times (e.g. "npt=-30"). When used in a PLAY         |
   request, the server treats this as a request to start/resume playback |
   from the current pause point, ending at the end time specified in the |
   Range header.

10.6 PAUSE

   The PAUSE request causes the stream delivery to be interrupted
   (halted) temporarily. If the request URL names a stream, only play-
   back and recording of that stream pause point is halted. For example, for audio,
   this located later than the given end  |
   value, a 457 (Invalid Range) response SHALL be given.                 |

   The queued play functionality described in RFC 2326 [21] is equivalent removed   |
   and multiple ranges can be used to muting. achieve a similar performance. If  |
   a server receives a PLAY request while in the PLAY state, the server  |
   SHALL responde using the error code 455 (Method Not Valid In This     |
   State). This will signal the client that queued play are not sup-     |
   ported.                                                               |

   The use of PLAY for keep-alive signaling, i.e. PLAY request URL names without a presentation |
   range header, has also been decapitated.  Instead a client can use,   |
   PING, SET_PARAMETER or group OPTIONS for keep alive. A server receiving a   |
   PLAY keep alive SHALL respond with the 455 error code.                |

   When playing live media, indicated by the Transport headers mode      |
   parameter the session are in a live state. This live state will put   |
   some restrictions on the action available for a client. A PLAY        |
   request without a Range header will start media deliver at the cur-   |
   rent point in the live presentation, i.e. now. Any seeking in the     |
   media will be impossible. The only allowed usage of streams, delivery the Range header  |
   is npt=now-, and certain clock units. The usage of all currently active streams within npt=now- is unnec- |
   essary as it has the presentation exact same meaning as a request without Range    |
   header. The clock format can be used to specify start and stop times  |
   for media delivery in a live session.                                 |

10.6 PAUSE

   The PAUSE request causes the stream delivery to be interrupted        |
   (halted) temporarily. A PAUSE request MUST be done with the aggre-    |
   gated control URI for aggregated sessions, resulting in all media     |
   being halted, or group is halted. the media URI for non-aggregated sessions. Any       |
   attempt to do muting of a single media with an PAUSE request in an    |
   aggregated session SHALL be responded with error 460 (Only Aggregate  |
   Operation Allowed). After resuming playback or recording, synchronization synchro-    |
   nization of the tracks MUST be maintained. Any server resources are   |
   kept, though servers MAY close the session and free resources after   |
   being paused for the duration specified with the timeout parameter of |
   the Session header in the SETUP message.

   Example:

     C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0
           CSeq: 834
           Session: 12345678

     S->C: RTSP/1.0 200 OK
           CSeq: 834
           Date: 23 Jan 1997 15:35:06 GMT
           Range: npt=45.76

   The PAUSE request may contain a Range header specifying when the      |
   stream or presentation is to be halted. We refer to this point as the |
   "pause point". The header must MUST contain a single value, expressed as   |
   the beginning value an open range. For example, the following clip    |
   will be played from 10 seconds through 21 seconds of the clip's nor-  |
   mal play time: time, under the assumption that the PAUSE request reaches    |
   the server within 11 seconds of the PLAY request. Note that some      |
   lines has been broken in an non-correct way to fit the page:          |

     C->S: PLAY rtsp://example.com/fizzle/foo RTSP/1.0                   |
           CSeq: 834                                                     |
           Session: 12345678                                             |
           Range: npt=10-30                                              |
     S->C: RTSP/1.0 200 OK                                               |
           CSeq: 834                                                     |
           Date: 23 Jan 1997 15:35:06 GMT                                |
           Server: PhonyServer 1.0                                       |
           Range: npt=10-30                                              |
           RTP-Info:url=rtsp://example.com/fizzle/foo/audiotrack;seq=5712;rtptime=934207921,|
                   url=rtsp://example.com/fizzle/foo/videotrack;seq=57654;rtptime=2792482193|
           RTP-Info:url=rtsp://example.com/fizzle/audiotrack;            |
                   seq=5712;rtptime=934207921,                           |
                   url=rtsp://example.com/fizzle/videotrack;             |
                   seq=57654;rtptime=2792482193                          |
           Session: 12345678                                             |

     C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0                  |
           CSeq: 835                                                     |
           Session: 12345678                                             |
           Range: npt=21-                                                |

     S->C: RTSP/1.0 200 OK                                               |
           CSeq: 835                                                     |
           Date: 23 Jan 1997 15:35:09 GMT                                |
           Server: PhonyServer 1.0                                       |
           Range: npt=21-                                                |

   The normal play time for the stream is set to the pause point.
           Session: 12345678                                             |

   The pause request becomes effective the first time the server is encoun-
   tering      |
   encountering the time point specified in any of the currently pending PLAY
   requests. multiple ranges.  |
   If the Range header specifies a time outside any currently
   pending range from the PLAY requests,  |
   request, the error 457 (Invalid Range) is SHALL be returned. If a media  |
   unit (such as an audio or video frame) starts presentation at exactly |
   the pause point, it is not played or recorded. If the Range header is |
   missing, stream delivery is interrupted immediately on receipt of the |
   message and the pause point is set to the current nor-
   mal normal play time.

   A PAUSE request discards all queued PLAY requests.   |
   However, the pause point in the media stream MUST be maintained. A    |
   subsequent PLAY request without Range header resumes from the pause point.   |
   point and play until media end.                                       |

   The actual pause point after any PAUSE request SHALL be returned to   |
   the client by adding a Range header with what remains unplayed of the |
   PLAY request's ranges, i.e. including all the remaining ranges part   |
   of multiple range specification. If one desires to resume playing a   |
   ranged request, one simple included the Range header from the PAUSE   |
   response.                                                             |

   For example, if the server has have a play requests request for ranges 10 to 15    |
   and 20 to 29 pending and then receives a pause request for NPT 21, it |
   would start playing the second range and stop at NPT 21. If the pause |
   request is for NPT 12 and the server is playing at NPT 13 serving the |
   first play request, the server stops immediately. If the pause        |
   request is for NPT 16, the server returns a 457 error message. To     |
   prevent that the second range is played and the server stops after    |
   completing the first
   play range, a PAUSE request and discards the second play request. for 20 must be issued.    |

   As another example, if a server has received requests to play ranges  |
   10 to 15 and then 13 to 20 (that is, overlapping ranges), the PAUSE   |
   request for NPT=14 would take effect while the server plays the first |
   range, with the second PLAY request range effectively being ignored, assum-
   ing assuming the  |
   PAUSE request arrives before the server has started playing the second, sec-  |
   ond, overlapping range. Regardless of when the PAUSE request arrives, |
   it sets the NPT pause point to 14.                                        |

   If the server has already sent data beyond the time specified in the  |
   the PAUSE request Range header, a PLAY without range would still      |
   resume at that point in time, specified by the pause's range header,  |
   as it is assumed that the client has discarded data after that point. |
   This ensures continuous pause/play cycling without gaps.

10.7 TEARDOWN

   The TEARDOWN request stops the stream delivery for the given URI,     |
   freeing the resources associated with it. If the URI is the presenta-
   tion aggre-    |
   gated control URI for this presentation, any RTSP session identifier associ-
   ated  |
   associated with the session is no longer valid. Unless all transport param-
   eters are defined by The use of "*" as URI |
   in TEARDOWN will also result in that the session description, a SETUP is removed indepen-  |
   dent of the number of medias that was part of it. If the URI in the   |
   request has to
   be issued before was for a media within an aggregated session that media is    |
   removed from the aggregate. However the session and any other media   |
   stream yet not torn down remains, and any valid request, e.g. PLAY or |
   SETUP, can be played again.

   A issued. As an optional feature a server MAY keep the    |
   session in case the last remaining media is torn down with a TEARDOWN |
   request with an URI equal to the media URI. To Indicate what has been |
   performed, a server that after processing the any TEARDOWN request, still has a      |
   valid session MUST in the response return a session header.           |

   A server MAY choose to allow TEARDOWN of individual media while in    |
   PLAY state. When this is not allowed the response SHALL be 455        |
   (Method Not Valid In This State). If a server implements TEARDOWN and |
   SETUP in PLAY state it MUST signal this using the "setup.playing"     |
   option tag.                                                           |

   Example:

     C->S: TEARDOWN rtsp://example.com/fizzle/foo RTSP/1.0
           CSeq: 892
           Session: 12345678

     S->C: RTSP/1.0 200 OK
           CSeq: 892
           Server: PhonyServer 1.0

10.8 GET_PARAMETER

   The GET_PARAMETER request retrieves the value of a parameter of a     |
   presentation or stream specified in the URI. If the Session header is |
   present in a request, the value of a parameter MUST be retrieved in   |
   the sessions context. The content of the reply and response is left   |
   to the implementation.  GET_PARAMETER with no entity body may be used |
   to test client or server liveness ("ping").  Example:

     S->C: GET_PARAMETER rtsp://example.com/fizzle/foo RTSP/1.0
           CSeq: 431
           Content-Type: text/parameters
           Session: 12345678
           Content-Length: 15

           packets_received
           jitter

     C->S: RTSP/1.0 200 OK
           CSeq: 431
           Content-Length: 46
           Content-Type: text/parameters

           packets_received: 10
           jitter: 0.3838

     The "text/parameters" section is only an example type for
     parameter. This method is intentionally loosely defined with
     the intention that the reply content and response content will
     be defined after further experimentation.

10.9 SET_PARAMETER

   This method requests to set the value of a parameter for a presenta-
   tion or stream specified by the URI.

   A request SHOULD is RECOMMENDED to only contain a single parameter to allow  |
   the client to determine why a particular request failed. If the       |
   request contains several parameters, the server MUST only act on the  |
   request if all of the parameters can be set successfully. A server    |
   MUST allow a parame-
   ter parameter to be set repeatedly to the same value, but it |
   MAY disallow changing parameter values.  If the receiver of the       |
   request does not understand or can locate a parameter error 451       |
   (Parameter Not Understood) SHALL be used.  In the case a parameter is |
   not allowed to change the error code 458 (Parameter Is Read-Only).    |
   The response body SHOULD contain only the parameters that has errors. |
   Otherwise no body SHALL be returned.

   Note: transport parameters for the media stream MUST only be set with
   the SETUP command.

     Restricting setting transport parameters to SETUP is for the
     benefit of firewalls.

     The parameters are split in a fine-grained fashion so that
     there can be more meaningful error indications. However, it
     may make sense to allow the setting of several parameters if
     an atomic setting is desirable. Imagine device control where
     the client does not want the camera to pan unless it can also
     tilt to the right angle at the same time.

   Example:

     C->S: SET_PARAMETER rtsp://example.com/fizzle/foo RTSP/1.0
           CSeq: 421
           Content-length: 20
           Content-type: text/parameters

           barparam: barstuff

     S->C: RTSP/1.0 451 Parameter Not Understood
           CSeq: 421
           Content-length: 10
           Content-type: text/parameters

           barparam

     The "text/parameters" section is only an example type for
     parameter. This method is intentionally loosely defined with
     the intention that the reply content and response content will
     be defined after further experimentation.

10.10 REDIRECT

   A redirect request informs the client that it must MUST connect to another |
   server location. It contains REDIRECT SHALL only be sent to the client who cur-   |
   rently has a session at the server. The REDIRECT request MAY contain  |
   the mandatory header Location, which indicates that the client should issue     |
   requests for that URL. It may If the Location URL only contains a host       |
   address the client shall connect to the given host, while using the   |
   path from the URL on the current server.                              |

   The redirect request MAY contain the parameter header Range, which indicates    |
   when the redirection takes effect. If the client wants to continue to send or receive
   media for this URI, the client MUST issue Range contains a TEARDOWN request for time=      |
   value that is the
   current session and a SETUP for wall clock time that the new session redirection MUST at the designated
   host.

   This example request redirects traffic for this URI to    |
   latest take place. When the new server
   at time= parameter is present the given play time:

     S->C: REDIRECT rtsp://example.com/fizzle/foo RTSP/1.0
           CSeq: 732
           Location: rtsp://bigserver.com:8001
           Range: clock=19960213T143205Z-

10.11 RECORD

   This method initiates recording a range of media data according to      |
   value MUST be ignored.  However the presentation description. The timestamp reflects start range entered MUST be syntactical |
   correct and end
   time (UTC). SHALL point at the beginning of any on-demand content. If |
   no time range parameter is given, use part of the Range header then redirection SHALL  |
   take place when the media playout from the server reaches the given   |
   time. The range value MUST be a single value in the open ended form,  |
   e.g. npt=59-.                                                         |

   If a Session header is included in the REDIRECT request the client    |
   MUST redirect the indicated session. If no Session header is included |
   the client MUST redirect all sessions that it have on the server      |
   sending the request.                                                  |

   If the client wants to continue to send or receive media for this     |
   resource, the client MUST issue a TEARDOWN request for the current    |
   session. A new session must be established with the designated host.  |
   A client SHOULD issue a new DESCRIBE request with the URL given in    |
   the Location header, unless the URL only contains a host address. In  |
   the cases the Location only contains a host address the client MAY    |
   assume that the media on the server it is redirected to is identical. |
   Identical media means that all media configuration information from   |
   the old session still is valid except for the host address. In the    |
   case of absolute URLs in the location header the media redirected to  |
   can be either identical, slightly different or totally different.     |
   This is the reason why a new DESCRIBE request SHOULD be issued.       |

   This example request redirects traffic for this session to the new    |
   server at the given absolute time:                                    |

     S->C: REDIRECT rtsp://example.com/fizzle/foo RTSP/1.0               |
           CSeq: 732                                                     |
           Location: rtsp://bigserver.com:8001                           |
           Range: clock=19960213T143205Z-                                |
           Session: uZ3ci0K+Ld-M                                         |

10.11 RECORD

   This method initiates recording a range of media data according to
   the presentation description. The timestamp reflects start and end
   time (UTC). If no time range is given, use the start or end time pro-
   vided in the presentation description. If the session has already
   started, commence recording immediately.

   The server decides whether to store the recorded data under the
   request-URI or another URI. If the server does not use the request-
   URI, the response SHOULD be 201 (Created) and contain an entity which
   describes the status of the request and refers to the new resource,
   and a Location header.

   A media server supporting recording of live presentations MUST sup-
   port the clock range format; the smpte format does not make sense.

   In this example, the media server was previously invited to the con-
   ference indicated.

     C->S: RECORD rtsp://example.com/meeting/audio.en RTSP/1.0
           CSeq: 954
           Session: 12345678
           Conference: 128.16.64.19/32492374

     Note: this example needs work, or needs to be removed.  More
     thoughts on how it works together with ANNOUNCE is needed.
     Also notification on out of disk is needed. The use of aggre-
     gated and non-aggregated control needs to be clarified.

10.12 PING                                                               |

   This method is a bi-directional mechanism for server or client live-  |
   ness checking. It has no side effects. The issuer of the request MUST |
   include a session header with the session ID of the session that is   |
   being checked for liveness.                                           |
   Prior to using this method, an OPTIONS method MUST is RECOMMENDED to be    |
   issued in the   | direction which the PING method would be used. This     |
   method MUST NOT   | be used if support is not indicated by the Public     |
   header. Note: That an 501 (Not Implemented) response means that the   |
   keep-alive timer has not been updated.                                |

   When a proxy is in use, PING with a * indicates a single-hop liveness |
   check, whereas PING with a URL including an host address indicates an |
   end-to-end liveness       | check.                                            |

   Example:                                                              |

     C->S: PING * RTSP/1.0                                               |
           CSeq: 123                                                     |
           Session:12345678                                              |

     S->C: RTSP/1.0 200 OK                                               |
           CSeq: 123                                                     |
           Session:12345678                                              |

10.13 Embedded (Interleaved) Binary Data

   Certain firewall designs and other circumstances may force a server   |
   to interleave RTSP methods and stream data. This interleaving should  |
   generally be avoided unless necessary since it complicates client and |
   server operation and imposes additional overhead. Also head of line   |
   blocking may cause problems.  Interleaved binary data SHOULD only be  |
   used if RTSP is carried over TCP.

   Stream data such as RTP packets is encapsulated by an ASCII dollar
   sign (24 decimal), followed by a one-byte channel identifier, fol-
   lowed by the length of the encapsulated binary data as a binary, two-
   byte integer in network byte order. The stream data follows immedi-
   ately afterwards, without a CRLF, but including the upper-layer pro-
   tocol headers. Each $ block contains exactly one upper-layer protocol
   data unit, e.g., one RTP packet.

   The channel identifier is defined in the Transport header with the
   interleaved parameter(Section 12.40).

   When the transport choice is RTP, RTCP messages are also interleaved
   by the server over the TCP connection. As a default, RTCP packets are
   sent on the first available channel higher than the RTP channel. The
   client MAY explicitly request RTCP packets on another channel. This
   is done by specifying two channels in the interleaved parameter of
   the Transport header(Section 12.40).

     RTCP is needed for synchronization when two or more streams
     are interleaved in such a fashion. Also, this provides a con-
     venient way to tunnel RTP/RTCP packets through the TCP control
     connection when required by the network configuration and
     transfer them onto UDP when possible.

     C->S: SETUP rtsp://foo.com/bar.file RTSP/1.0
           CSeq: 2
           Transport: RTP/AVP/TCP;interleaved=0-1 RTP/AVP/TCP;unicast;interleaved=0-1

     S->C: RTSP/1.0 200 OK
           CSeq: 2
           Date: 05 Jun 1997 18:57:18 GMT
           Transport: RTP/AVP/TCP;interleaved=0-1 RTP/AVP/TCP;unicast;interleaved=0-1
           Session: 12345678

     C->S: PLAY rtsp://foo.com/bar.file RTSP/1.0
           CSeq: 3
           Session: 12345678

     S->C: RTSP/1.0 200 OK
           CSeq: 3
           Session: 12345678
           Date: 05 Jun 1997 18:59:15 GMT
           RTP-Info: url=rtsp://foo.com/bar.file;
             seq=232433;rtptime=972948234

     S->C: $000{2 byte length}{"length" bytes data, w/RTP header}
     S->C: $000{2 byte length}{"length" bytes data, w/RTP header}
     S->C: $001{2 byte length}{"length" bytes  RTCP packet}

11 Status Code Definitions

   Where applicable, HTTP status [H10] codes are reused. Status codes
   that have the same meaning are not repeated here. See Table 1 for a
   listing of which status codes may be returned by which requests. All
   error messages, 4xx and 5xx MAY return a body containing further
   information about the error.

11.1 Success 2xx 1xx

11.1.1 100 Continue

   See, [H10.1.1].

11.2 Success 2xx

11.2.1 250 Low on Storage Space

   The server returns this warning after receiving a RECORD request that
   it may not be able to fulfill completely due to insufficient storage
   space. If possible, the server should use the Range header to indi-
   cate what time period it may still be able to record. Since other
   processes on the server may be consuming storage space simultane-
   ously, a client should take this only as an estimate.

11.2

11.3 Redirection 3xx

   See [H10.3]. [H10.3] for definition of status code 300 to 305. However com-    |
   ments are given for some to how they apply to RTSP. Further a couple  |
   of new status codes are defined.                                      |

   Within RTSP, redirection may be used for load balancing or redirect-  |
   ing stream requests to a server topologically closer to the client.   |
   Mechanisms to determine topological proximity are beyond the scope of |
   this specification.

11.3 Client Error 4xx

11.4 400 Bad Request                                                   |

11.3.1 300 Multiple Choices                                              |

11.3.2 301 Moved Permanently                                             |

   The request could not be understood resource are moved permanently and resides now at the URI |
   given by the server due to malformed
   syntax. location header. The user client SHOULD NOT repeat redirect auto-   |
   matically to the request without modifica-
   tions [H10.4.1]. If given URI.                                           |

11.3.3 302 Found                                                         |

   The requested resource reside temporarily at the request does not have a CSeq header, URI given by the
   server     |
   Location header. The Location header MUST not include a be included.                |

11.3.4 303 See Other                                                     |

   This status code SHALL NOT be used in RTSP. However as it was allowed |
   to use in RFC 2326 it is possible that such response will be          |
   received.                                                             |

11.3.5 304 Not Modified                                                  |

11.3.6 305 Use Proxy                                                     |

   See [H10.3.6].                                                        |

11.3.7 350 Going Away                                                    |

   The server the request was directed at will not be available any      |
   more. This can be for a number of reasons, such as maintenance, or    |
   power failure. If there is a alternative server available the Loca-   |
   tion header SHOULD contain a URI to the same resource at that host.   |
   In case that no server is available the Location header MUST NOT be   |
   included.                                                             |

   In the case the client has an established session on the server giv-  |
   ing the 350 response code, it SHALL immediately do TEARDOWN on that   |
   session. It is RECOMMENDED that the server tries to send REDIRECT     |
   request if possible instead of waiting for a client request to        |
   responde to.                                                          |

11.3.8 351 Load Balancing                                                |

   The server the request was issued for is currently uneven loaded and  |
   request that further request is directed to another server.  The      |
   Location header MUST be included in the response and contain the URI  |
   of the other server. If the both server has the requested resource in |
   the same place only the Server part of the URI MAY be given. In all   |
   other cases an absolute URI MUST be given.

11.4 Client Error 4xx

11.4.1 400 Bad Request

   The request could not be understood by the server due to malformed
   syntax. The client SHOULD NOT repeat the request without modifica-
   tions [H10.4.1]. If the request does not have a CSeq header, the
   server MUST NOT include a CSeq in the response.

11.4.1

11.4.2 405 Method Not Allowed

   The method specified in the request is not allowed for the resource
   identified by the request URI. The response MUST include an Allow
   header containing a list of valid methods for the requested resource.
   This status code is also to be used if a request attempts to use a
   method not indicated during SETUP, e.g., if a RECORD request is
   issued even though the mode parameter in the Transport header only
   specified PLAY.

11.4.2

11.4.3 451 Parameter Not Understood

   The recipient of the request does not support one or more parameters  |
   contained in the request.

11.4.3 request.When returning this error message the sender |
   SHOULD return a entity body containing the offending parameter(s).

11.4.4 452 reserved

   This error code was removed from RFC 2326 [21] and is obsolete.

11.4.4

11.4.5 453 Not Enough Bandwidth

   The request was refused because there was insufficient bandwidth.
   This may, for example, be the result of a resource reservation fail-
   ure.

11.4.5

11.4.6 454 Session Not Found

   The RTSP session identifier in the Session header is missing,
   invalid, or has timed out.

11.4.6

11.4.7 455 Method Not Valid in This State

   The client or server cannot process this request in its current
   state.  The response SHOULD contain an Allow header to make error
   recovery easier.

11.4.7

11.4.8 456 Header Field Not Valid for Resource

   The server could not act on a required request header. For example,   |
   if PLAY contains the Range header field but the stream does not allow |
   seeking.

11.4.8 This error message may also be used for specifying when the  |
   time format in Range is impossible for the resource. In that case the |
   Accept-Ranges header SHOULD be returned to inform the client of which |
   format(s) that are allowed.

11.4.9 457 Invalid Range

   The Range value given is out of bounds, e.g., beyond the end of the
   presentation.

11.4.9

11.4.10 458 Parameter Is Read-Only

   The parameter to be set by SET_PARAMETER can be read but not modi-    |
   fied.

11.4.10 When returning this error message the sender SHOULD return a    |
   entity body containing the offending parameter(s).

11.4.11 459 Aggregate Operation Not Allowed

   The requested method may not be applied on the URL in question since
   it is an aggregate (presentation) URL. The method may be applied on a
   stream
   media URL.

11.4.11

11.4.12 460 Only Aggregate Operation Allowed

   The requested method may not be applied on the URL in question since  |
   it is not an aggregate control (presentation) URL. The method may be  |
   applied on the presentation aggregate control URL.

11.4.12

11.4.13 461 Unsupported Transport

   The Transport field did not contain a supported transport specifica-
   tion.

11.4.13

11.4.14 462 Destination Unreachable

   The data transmission channel could not be established because the
   client address could not be reached. This error will most likely be
   the result of a client attempt to place an invalid Destination param-
   eter in the Transport field.

11.5 Server Error 5xx

11.5.1 551 Option not supported

   An option given in the Require or the Proxy-Require fields was not
   supported. The Unsupported header should SHOULD be returned stating the
   option for which there is no support.

12 Header Field Definitions

   The general syntax for header fields is covered in Section 4.2 This   |
   section lists the full set of header fields along with notes on       | syn-
   tax, meaning, and usage.  Throughout this section, we use [HX.Y] to
   refer to Section X.Y of the current HTTP/1.1 specification RFC 2616
   [26].  Examples of each header field are given.

   Information about header fields in relation to methods and proxy pro-
   cessing is summarized in Table 4 and Table 5.

   The "where" column describes the request and response types in which
   the header field can be used. Values in this column are:

     R: header field may only appear in requests;

     r: header field may only appear in responses;

     2xx, 4xx, etc.: A numerical value or range indicates response codes
          with which the header field can be used;
             method        direction  object requirement acronym Body
   -----------------------------------------------------------
             -----------------------------------------------
             DESCRIBE      C->S       P,S    recommended    DES     r
             ANNOUNCE      C->S, S->C P,S    optional    ANN     R
             GET_PARAMETER C->S, S->C P,S    optional    GPR     R,r
             OPTIONS       C->S       P,S    required    OPT
                           S->C              optional
             PAUSE         C->S       P,S    recommended    PSE
             PING          C->S, S->C P,S    optional    PNG
             PLAY          C->S       P,S    required    PLY
             RECORD        C->S       P,S    optional    REC
             REDIRECT      S->C       P,S    optional    RDR
             SETUP         C->S       S      required      STP
             SET_PARAMETER C->S, S->C P,S    optional    SPR     R,r?     R,r
             TEARDOWN      C->S       P,S    required    TRD

   Table 3: Overview of RTSP methods, their direction, and what  objects
   (P:  presentation, S: stream) they operate on. Body notes if a method
   is allowed to carry  body  and  in  which  direction,  R  =  Request,
   r=response. Note:  There  has  been some usage of the body to convey
   more information in error messages It is allowed for  responses  containing  error
   codes. Some all error messages seem to mandate such usage.

   syntax, meaning, 4xx and usage.  Throughout this section, we use [HX.Y]   |
   to refer to Section X.Y of the current HTTP/1.1 specification RFC     |
   2616 [26].  Examples of each header field are given.                  |

   Information about header fields in relation 5xx to methods and proxy pro- |
   cessing is summarized in Table 4.                                     |

   The "where" column describes the request and response types in which  |
   the header field can be used. Values in this column are:              |

     R: header field may only appear in requests;                        |

     r: header field may only appear in responses;                       |

     2xx, 4xx, etc.: A numerical value or range indicates response codes |
          with which the header field can be used;                       |
   have a body

     c: header field is copied from the request to the response.         |

   An empty entry in the "where" column indicates that the header field  |
   may be present in all requests and responses.                         |

   The "proxy" column describes the operations a proxy may perform on a  |
   header field:                                                         |

     a: A proxy can add or concatenate the header field if not present.  |

     m: A proxy can modify an existing header field value.               |

     d: A proxy can delete a header field value.                         |

     r: A proxy must be able to read the header field, and thus this     |
          header field cannot be encrypted.                              |

   The rest of the columns relate to the presence of a header field in a |
   method. The method names when abbreviated, are abbreviated according to table 3:        |

     c: Conditional; requirements on the header field depend on the con- |
          text of the message.                                           |

     m: The header field is mandatory.                                   |

     m*: The header field SHOULD be sent, but clients/servers need to be |
          prepared to receive messages without that header field.        |

     o: The header field is optional.                                    |

     t: The header field SHOULD be sent, but clients/servers need to be  |
          prepared to receive messages without that header field.  If a  |
          stream-based protocol (such as TCP) is used as a transport,    |
          then the header field MUST be sent.                            |

     *: The header field is required if the message body is not empty.   |
          See sections 12.14, 12.16 and 4.3 for details.                 |

     -: The header field is not applicable.                              |

   "Optional" means that a Client/Server MAY include the header field in |
   a request or response, and a Client/Server MAY ignore the header      |
   field if present in the request or response (The exception to this    |
   rule is the Require header field discussed in 12.32). A "mandatory"   |
   header field MUST be present in a request, and MUST be understood by  |
   the Client/Server receiving the request. A mandatory response header  |
   field MUST be present in the response, and the header field MUST be   |
   understood by the Client/Server processing the response. "Not         |
   applicable" appli-
   cable" means that the header field MUST NOT be present in a      | request.
   If one is placed in a request by mistake, it MUST be ignored | by the
   Client/Server receiving the request. Similarly, a header field |
   labeled "not applicable" for a response means that the Client/Server  |
   MUST NOT place the header field in the response, and the              |
   Client/Server MUST ignore the header field in the response.           |

   A Client/Server SHOULD ignore extension header parameters that are    |
   not understood.                                                       |

   The From, Location, and RTP-Info header fields contain a URI. If the  |
   URI contains a comma, or semicolon, the URI MUST be enclosed in dou-  |
   ble quotas ("). Any URI parameters are contained within these quotas. |
   If the URI is not enclosed in double quotas, any semicolon- delimited |
   parameters are header-parameters, not URI parameters.                 |

12.1 Accept                                                              |

   The Accept request-header field can be used to specify certain pre-
   sentation description content types which are acceptable for the
   response.

     The "level" parameter for presentation descriptions is prop-
     erly defined as part of the MIME type registration, not here.

   See [H14.1] for syntax.

   Example of use:

     Accept: application/rtsl, application/sdp;level=2

12.2 Accept-Encoding

   See [H14.3]

12.3 Accept-Language

   See [H14.4]. Note that the language specified applies to the presen-
   tation description and any reason phrases, not the media content.

12.4 Accept-Ranges                                                       |

   Header              Where  Proxy DES OPT GPR SPR ANN STP PLY REC PSE SETUP PLAY PAUSE TRD RDR PNG
   ---------------------------------------------------------------------------------
   --------------------------------------------------------------
   Accept                R           o   -    -    -     -   -   -   -   -   -   -   -
   Accept-Encoding       R      r    o   -    -    -     -   -   -   -   -   -   -   -
   Accept-Language       R      r    o   -    -    -     -   -
   Accept-Ranges         r      r    -   -   -    o    -     -   -
   Accept-Ranges        456     r    -   -    -    o     o   -   -
   Allow                 r           -   o    -    -     -   -   -
   Allow                405          -   -    -   -   m   -   m    m     m   -   -   -
   Authorization         R           o   o    o    o     o   o   o   o   o   o   o   o
   Bandwidth             R           o   -   -   o   -    o    o     -   -   -   -   -
   Blocksize             R           o   -   -   o   -    o    o     -   -   -   -   -
   Cache-Control                r    -   -   -   -   -    o    -     -   -   -   -   -
   Connection                        o   o    o    o     o   o   o   o   o   o   o   -
   Content-Base          R           -   -   o   o   o   -   -   -   -   -   -   -
   Content-Base          r           o   -   o   o   -   -   -   -    -    -     -   -
   Content-Base         4xx          o   o    o    o     o   o   o   o   o   o   o   -
   Content-Encoding      R      r    -   -   o   o   o   -   -   -    -    -     -   -
   Content-Encoding      r      r    o   -   o   o   -   -   -   -    -    -     -   -
   Content-Encoding     4xx     r    o   o    o    o     o   o   o   o   o   o   o   -
   Content-Language      R      r    -   -   o   o   o   -   -   -    -    -     -   -
   Content-Language      r      r    o   -   o   o   -   -   -   -    -    -     -   -
   Content-Language     4xx     r    o   o    o    o     o   o   o   o   o   o   o   -
   Content-Length        R      r    -   -   *   *   *   -   -   -   -   -   -   -
   Content-Length        r      r    *   -   *   *   -   -   -   -    -    -     -   -
   Content-Length       4xx     r    *   *    *    *     *   *   *   *   *   *   *   -
   Content-Location      R           -   -   o   o   o   -   -   -   -   -   -   -
   Content-Location      r           o   -   o   o   -   -   -   -    -    -     -   -
   Content-Location     4xx          o   o    o    o     o   o   o   o   o   o   o   -
   Content-Type          R           -   -   *   *   *   -   -   -   -   -   -   -
   Content-Type          r           *   -   *   *   -   -   -   -    -    -     -   -
   Content-Type         4xx          *   *    *    *     *   *   *   *   *   *   *   -
   CSeq                 Rc           m   m    m    m     m   m   m   m   m   m   m   m
   Date                        am    o   o    o    o     o   o   o   o   o   o   o   o
   Expires               r      r    o   -    -    -     -   -   -   -   -   -   -   -
   From                  R      r    o   o    o    o     o   o   o   o   o   o   o   o
   Host                              o   o    o    o     o   o   o   o   o   o   o   o
   If-Match              R      r    -   -   -   -   -    o    -     -   -   -   -   -
   If-Modified-Since     R      r    o   -   -   -   -   o   -   -   -   -   -   -
   Last-Modified         R      r    -   -   -   -    o    -     -   -   -   -   -   -
   Last-Modified         r      r    o   -   o   -    -    -     -   -   -   -   -   -
   Location              R           -   -   -   -   -   -   -   -   -   -   m   -
   Location             3xx          m   -   -   -   -   m   -   -          o   -    o    -     -   -
   Proxy-Authenticate   407    amr   m   m    m    m     m   m   m   m   m   m   m   m
   Proxy-Require         R     ar    o   o    o    o     o   o   o   o   o   o   o   o
   Public                r    admr   -  m*    -    -     -   -   -   -   -   -   -   -
   Public               501   admr  m*  m*   m*    m*   m*   m*  m*  m*  m*  m*  m*  m*
   Range                 R           -   -    -   -   -   -   o   -    o   -     o   -
   Range                 r           -   -   -   -   -   -    c    m*    -   -   -   -   -
   Referer               R           o   o    o    o     o   o   o   o   o   o   o   -
   Require               R           o   o    o    o     o   o   o   o   o   o   o   o
   Retry-After        3xx,503        o   o    o   o   -   o   -   -   -    -     -   -
   RTP-Info              r           -   -   -   -   -   -    o    m     -   -   -   -   -
   Scale                             -   -    -   -   -   -   o    o     -   -   -   -
   Session               R           -   o    o   o   m   o   m   m   m    m     m   m
   Session               r           -   c   c   c   m   m    m    m     m   o   m   m
   Server                R           -   o   o   o   o   -    -    -     -   -   o   o
   Server                r           o   o    o    o     o   o   o   o   o   o   -   o
   Speed                             -   -    -   -   -   -    o     -   -   -   -   -
   Supported             R           o   o    o    o     o   o   o   o   o   o   o   o
   Supported             r           c   c    c    c     c   c   c   c   c   c   c   c
   Timestamp             R           o   o    o    o     o   o   o   o   o   o   o   o
   Timestamp             c           m   m    m    m     m   m   m   m   m   m   m   m
   Transport                         -   -   -   -   -    m    -     -   -   -   -   -
   Unsupported           r           c   c    c    c     c   c   c   c   c   c   c   c
   User-Agent            R          m*  m*   m*    m*   m*   m*  m*  m*  m*  m*   -   -
   User-Agent            r           -   -   -   -   -   -   -   -   -   -  m*   -
   Vary                  r           c   c    c    c     c   c   c   c   c   c   -   -
   Via                   R     amr   o   o    o    o     o   o   o   o   o   o   o   o
   Via                   c     dr    m   m    m    m     m   m   m   m   m   m   m   m
   WWW-Authenticate     401          m   m    m    m     m   m   m   m   m   m   m   m
   ---------------------------------------------------------------------------------
   --------------------------------------------------------------
   Header              Where  Proxy DES OPT GPR SPR ANN STP PLY REC PSE SETUP PLAY PAUSE TRD RDR PNG

   Table  4: Overview of RTSP header fields

12.5 Allow

   The Allow entity-header field lists the methods supported by the
   resource identified by the request-URI. The purpose of this field is related to strictly inform the recipient of valid methods associated with the
   resource. An Allow header field must be present in a 405 (Method Not
   Allowed) response. DESCRIBE,
   OPTIONS, SETUP, PLAY, PAUSE, and TEARDOWN.

   See [H14.1] for syntax.

   Example of use:

     Allow: SETUP, PLAY, RECORD, SET_PARAMETER

12.6 Authorization

     Accept: application/rtsl q=1.0, application/sdp;level=2

12.2 Accept-Encoding

   See [H14.8]

12.7 Bandwidth

   The Bandwidth request-header field describes [H14.3]

12.3 Accept-Language

   See [H14.4]. Note that the estimated bandwidth
   available language specified applies to the client, expressed as a positive integer presen-
   tation description and measured
   in bits per second. The bandwidth available to any reason phrases, not the client may change
   during an RTSP session, e.g., due to modem retraining. media content.

12.4 Accept-Ranges                                                       |
   Header              Where  Proxy GPR SPR ANN REC RDR PNG
   ---------------------------------------------------------
   Allow                405          -   -   m   m   -   -
   Authorization         R           o   o   o   o   o   o
   Bandwidth  =  "Bandwidth" ":" 1*DIGIT

   Example:

     Bandwidth: 4000

12.8 Blocksize

   The             R           -   o   -   -   -   -
   Blocksize request-header field is sent from the client to the
   media server asking the server for a particular media packet size.
   This packet size does not include lower-layer headers such as IP,
   UDP, or RTP. The server is free to use a blocksize which is lower
   than the one requested. The server MAY truncate this packet size to
   the closest multiple of the minimum, media-specific block size, or
   override it with the media-specific size if necessary. The block size
   MUST be a positive decimal number, measured in octets.             R           -   o   -   -   -   -
   Connection                        o   o   o   o   o   -
   Content-Base          R           o   o   o   -   -   -
   Content-Base          r           o   o   -   -   -   -
   Content-Base         4xx          o   o   o   o   o   -
   Content-Encoding      R      r    o   o   o   -   -   -
   Content-Encoding      r      r    o   o   -   -   -   -
   Content-Encoding     4xx     r    o   o   o   o   o   -
   Content-Language      R      r    o   o   o   -   -   -
   Content-Language      r      r    o   o   -   -   -   -
   Content-Language     4xx     r    o   o   o   o   o   -
   Content-Length        R      r    *   *   *   -   -   -
   Content-Length        r      r    *   *   -   -   -   -
   Content-Length       4xx     r    *   *   *   *   *   -
   Content-Location      R           o   o   o   -   -   -
   Content-Location      r           o   o   -   -   -   -
   Content-Location     4xx          o   o   o   o   o   -
   Content-Type          R           *   *   *   -   -   -
   Content-Type          r           *   *   -   -   -   -
   Content-Type         4xx          *   *   *   *   *   -
   CSeq                 Rc           m   m   m   m   m   m
   Date                        am    o   o   o   o   o   o
   From                  R      r    o   o   o   o   o   o
   Host                              o   o   o   o   o   o
   Last-Modified         R      r    -   -   o   -   -   -
   Last-Modified         r      r    o   -   -   -   -   -
   Location              R           -   -   -   -   m   -
   Proxy-Authenticate   407    amr   m   m   m   m   m   m
   Proxy-Require         R     ar    o   o   o   o   o   o
   Public               501   admr  m*  m*  m*  m*  m*  m*
   Range                 R           -   -   -   -   o   -
   Referer               R           o   o   o   o   o   -
   Require               R           o   o   o   o   o   o
   Retry-After        3xx,503        o   o   -   -   -   -
   Scale                             -   -   -   o   -   -
   Session               R           o   o   m   m   o   m
   Session               r           c   c   m   m   o   m
   Server                R           o   o   o   -   o   o
   Server                r           o   o   o   o   -   o
   Supported             R           o   o   o   o   o   o
   Supported             r           c   c   c   c   c   c
   Timestamp             R           o   o   o   o   o   o
   Timestamp             c           m   m   m   m   m   m
   Unsupported           r           c   c   c   c   c   c
   User-Agent            R          m*  m*  m*  m*   -  m*
   User-Agent            r           -   -   -   -  m*   -
   Vary                  r           c   c   c   c   -   -
   Via                   R     amr   o   o   o   o   o   o
   Via                   c     dr    m   m   m   m   m   m
   WWW-Authenticate     401          m   m   m   m   m   m
   ---------------------------------------------------------
   Header              Where  Proxy GPR SPR ANN REC RDR PNG

   Table 5: Overview of RTSP header fields related to methods GET_PARAM-
   ETER, SET_PARAMETER, ANNOUNCE, RECORD, REDIRECT, and PING.

   The Accept-Ranges response-header field allows the server to indicate |
   its acceptance of range requests and possible formats for a resource: |

   Accept-Ranges       =  "Accept-Ranges" ":"                               ||
   acceptable-ranges                                                        ||
   acceptable-ranges   =  1#range-unit / "none"                             ||
   range-unit          =  NPT / SMPTE / UTC / LIVE                          ||

   This header has the same syntax as [H14.5]. However new range-units   |
   are defined and byte-ranges SHALL NOT be used.  Inclusion of any of   |
   the three time formats indicates acceptance by the server for PLAY    |
   and PAUSE requests with this format.  Inclusion of the "LIVE" tag     |
   indicates that the resource has LIVE properties. The headers value is |
   valid for the resource specified by the URI in the request, this      |
   response corresponds to.                                              |

   A server is RECOMMENDED to use this header in SETUP responses to      |
   indicate to the client which range time formats the media supports.   |
   The header SHOULD also be included in "456" responses which is a      |
   result of use of unsupported range formats.                           |

12.5 Allow

   The Allow entity-header field lists the methods supported by the
   resource identified by the request-URI. The purpose of this field is
   to strictly inform the recipient of valid methods associated with the
   resource. An Allow header field MUST be present in a 405 (Method Not
   Allowed) response. See [H14.7] for syntax definition.

   Example of use:

     Allow: SETUP, PLAY, RECORD, SET_PARAMETER

12.6 Authorization

   See [H14.8]

12.7 Bandwidth

   The Bandwidth request-header field describes the estimated bandwidth
   available to the client, expressed as a positive integer and measured
   in bits per second. The bandwidth available to the client may change
   during an RTSP session, e.g., due to modem retraining.

   Bandwidth  =  "Bandwidth" ":" 1*DIGIT

   Example:

     Bandwidth: 4000

12.8 Blocksize

   The Blocksize request-header field is sent from the client to the
   media server asking the server for a particular media packet size.
   This packet size does not include lower-layer headers such as IP,
   UDP, or RTP. The server is free to use a blocksize which is lower
   than the one requested. The server MAY truncate this packet size to
   the closest multiple of the minimum, media-specific block size, or
   override it with the media-specific size if necessary. The block size
   MUST be a positive decimal number, measured in octets. The server
   only returns an error (400) if the value is syntactically invalid.    |

   Blocksize  =  "Blocksize" ":" 1*DIGIT

12.9 Cache-Control
   The Cache-Control general-header field is used to specify directives
   that MUST be obeyed by all caching mechanisms along the
   request/response chain.

   Cache directives must be passed through by a proxy or gateway appli-
   cation, regardless of their significance to that application, since
   the directives may be applicable to all recipients along the
   request/response chain. It is not possible to specify a cache-direc-
   tive for a specific cache.

   Cache-Control should only be specified in a SETUP request and its
   response. Note: Cache-Control does not govern the caching of
   responses as for HTTP, but rather of the stream identified by the
   SETUP request. Responses to RTSP requests are not cacheable, except
   for responses to DESCRIBE.

   Cache-Control             =  "Cache-Control" ":" 1#cache-directive
   cache-directive           =  cache-request-directive
                            /   cache-response-directive
   cache-request-directive   =  "no-cache"
                            /   "max-stale" ["=" delta-seconds]
                            /   "min-fresh" "=" delta-seconds
                            /   "only-if-cached"
                            /   cache-extension
   cache-response-directive  =  "public"
                            /   "private"
                            /   "no-cache"
                            /   "no-transform"
                            /   "must-revalidate"
                            /   "proxy-revalidate"
                            /   "max-age" "=" delta-seconds
                            /   cache-extension
   cache-extension           =  token [ "=" ( token / quoted-string ) ]
   delta-seconds             =  1*DIGIT

     no-cache: Indicates that the media stream MUST NOT be cached any-
          where. This allows an origin server to prevent caching even by
          caches that have been configured to return stale responses to
          client requests.

     public: Indicates that the media stream is cacheable by any cache.

     private: Indicates that the media stream is intended for a single
          user and MUST NOT be cached by a shared cache. A private (non-
          shared) cache may cache the media stream.

     no-transform: An intermediate cache (proxy) may find it useful to
          convert the media type of a certain stream. A proxy might, for
          example, convert between video formats to save cache space or
          to reduce the amount of traffic on a slow link. Serious opera-
          tional problems may occur, however, when these transformations
          have been applied to streams intended for certain kinds of
          applications. For example, applications for medical imaging,
          scientific data analysis and those using end-to-end authenti-
          cation all depend on receiving a stream that is bit-for-bit
          identical to the original entity-body. Therefore, if a
          response includes the no-transform directive, an intermediate
          cache or proxy MUST NOT change the encoding of the stream.
          Unlike HTTP, RTSP does not provide for partial transformation
          at this point, e.g., allowing translation into a different
          language.

     only-if-cached: In some cases, such as times of extremely poor net-
          work connectivity, a client may want a cache to return only
          those media streams that it currently has stored, and not to
          receive these from the origin server. To do this, the client
          may include the only-if-cached directive in a request. If it
          receives this directive, a cache SHOULD either respond using a
          cached media stream that is consistent with the other con-
          straints of the request, or respond with a 504 (Gateway Time-
          out) status. However, if a group of caches is being operated
          as a unified system with good internal connectivity, such a
          request MAY be forwarded within that group of caches.

     max-stale: Indicates that the client is willing to accept a media
          stream that has exceeded its expiration time. If max-stale is
          assigned a value, then the client is willing to accept a
          response that has exceeded its expiration time by no more than
          the specified number of seconds. If no value is assigned to
          max-stale, then the client is willing to accept a stale
          response of any age.

     min-fresh: Indicates that the client is willing to accept a media
          stream whose freshness lifetime is no less than its current
          age plus the specified time in seconds. That is, the client
          wants a response that will still be fresh for at least the
          specified number of seconds.

     must-revalidate: When the must-revalidate directive is present in a
          SETUP response received by a cache, that cache MUST NOT use
          the entry after it becomes stale to respond to a subsequent
          request without first revalidating it with the origin server.
          That is, the cache must do an end-to-end revalidation every
          time, if, based solely on the origin server's Expires, the
          cached response is stale.)

     proxy-revalidate: The proxy-revalidate directive has the same mean- |
          ing as the must-revalidate directive, except that it does not  |
          apply to non-shared user agent caches. It can be used on a     |
          response to an authenticated request to permit the user's      |
          cache to store and later return the response without needing   |
          to revalidate it (since it has already been authenticated once |
          by that user), while still requiring proxies that service many |
          users to revalidate each time (in order to make sure that each |
          user has been authenticated). Note that such authenticated     |
          responses also need the public cache control directive in      |
          order to allow them to be cached at all.                       |

     max-age: When an intermediate cache is forced, by means of a max-   |
          age=0 directive, to revalidate its own cache entry, and the    |
          client has supplied its own validator in the request, the sup- |
          plied validator might differ from the validator currently      |
          stored with the cache entry. In this case, the cache MAY use   |
          either validator in making its own request without affecting   |
          semantic transparency.                                         |

          However, the choice of validator might affect performance. The |
          best approach is for the intermediate cache to use its own     |
          validator when making its request. If the server replies with  |
          304 (Not Modified), then the cache can return its now vali-    |
          dated copy to the client with a 200 (OK) response. If the      |
          server replies with a new entity and cache validator, however, |
          the intermediate cache can compare the returned validator with |
          the one provided in the client's request, using the strong     |
          comparison function. If the client's validator is equal to the |
          origin server's, then the intermediate cache simply returns    |
          304 (Not Modified). Otherwise, it returns the new entity with  |
          a 200 (OK) response.

12.10 Connection

   See [H14.10]. The use of the connection option "close" in RTSP mes-   |
   sages SHOULD be limited to error messages when the server is unable   |
   to recover and therefore see it necessary to close the connection.    |
   The reason is that the client shall have the choice of continue using |
   a connection indefinitely as long as it sends valid messages.

12.11 Content-Base

   The Content-Base entity-header field may be used to specify the base  |
   URI for resolving relative URLs within the entity.

   Content-Base  =  "Content-Base" ":" absoluteURI

   If no Content-Base field is present, the base URI of an entity is
   defined either by its Content-Location (if that Content-Location URI
   is an absolute URI) or the URI used to initiate the request, in that
   order of precedence. Note, however, that the base URI of the contents
   within the entity-body may be redefined within that entity-body.

12.12 Content-Encoding

   See [H14.11]

12.13 Content-Language

   See [H14.12]

12.14 Content-Length

   The Content-Length general-header field contains the length of the
   content of the method (i.e. after the double CRLF following the last
   header). Unlike HTTP, it MUST be included in all messages that carry
   content beyond the header portion of the message. If it is missing, a
   default value of zero is assumed. It is interpreted according to
   [H14.13].

12.15 Content-Location

   See [H14.14]

12.16 Content-Type

   See [H14.17]. Note that the content types suitable for RTSP are
   likely to be restricted in practice to presentation descriptions and
   parameter-value types.

12.17 CSeq

   The CSeq general-header field specifies the sequence number for an    |
   RTSP request-response pair. This field MUST be present in all         |
   requests and responses. For every RTSP request containing the given   |
   sequence number, the corresponding response will have the same num-   |
   ber. Any retransmitted request must contain the same sequence number  |
   as the original (i.e. the sequence number is not incremented for      |
   retransmissions of the same request). For each new RTSP request the   |
   CSeq value SHALL be incremented by one. The initial sequence number   |
   MAY be any number. Each sequence number series is unique between each |
   requester and responder, i.e. the client has one series for its       |
   request to a server and the server has another when sending request   |
   to the client.  Each requester and responder is identified with its   |
   network address.

   CSeq  =  "Cseq" ":" 1*DIGIT

12.18 Date

   See [H14.18]. An RTSP message containing a body MUST include a Date   |
   header if the sending host has a clock. Servers SHOULD include a Date |
   header in all other RTSP messages.

12.19 Expires

   The Expires entity-header field gives a date and time after which the
   description or media-stream should be considered stale. The interpre-
   tation depends on the method:

     DESCRIBE response: The Expires header indicates a date and time
          after which the description should be considered stale.

   A stale cache entry may not normally be returned by a cache (either a
   proxy cache or an user agent cache) unless it is first validated with
   the origin server (or with an intermediate cache that has a fresh
   copy of the entity). See section 13 for further discussion of the
   expiration model.

   The presence of an Expires field does not imply that the original
   resource will change or cease to exist at, before, or after that
   time.

   The format is an absolute date and time as defined by HTTP-date in
   [H3.3]; it MUST be in RFC1123-date format:

   Expires  =  "Expires" ":" HTTP-date

   An example of its use is

     Expires: Thu, 01 Dec 1994 16:00:00 GMT
   RTSP/1.0 clients and caches MUST treat other invalid date formats,
   especially including the value "0", as having occurred in the past
   (i.e., already expired).

   To mark a response as "already expired," an origin server
   only returns should use  |
   an error (416) Expires date that is equal to the Date header value. To mark a     |
   response as "never expires," an origin server SHOULD use an Expires   |
   date approximately one year from the time the response is sent.       |
   RTSP/1.0 servers SHOULD NOT send Expires dates more than one year in  |
   the future.

   The presence of an Expires header field with a date value of some
   time in the future on a media stream that otherwise would by default
   be non-cacheable indicates that the media stream is cacheable, unless
   indicated otherwise by a Cache-Control header field (Section 12.9).

12.20 From

   See [H14.22].

12.21 Host

   The Host HTTP request header field [H14.23] is not needed for RTSP.
   It should be silently ignored if sent.

12.22 If-Match

   See [H14.24].

   The If-Match request-header field is especially useful for ensuring
   the integrity of the presentation description, in both the case where
   it is fetched via means external to RTSP (such as HTTP), or in the
   case where the server implementation is guaranteeing the integrity of
   the description between the time of the DESCRIBE message and the
   SETUP message.

   The identifier is an opaque identifier, and thus is not specific to
   any particular session description language.

12.23 If-Modified-Since

   The If-Modified-Since request-header field is used with the DESCRIBE
   and SETUP methods to make them conditional. If the requested variant
   has not been modified since the time specified in this field, a
   description will not be returned from the server (DESCRIBE) or a
   stream will not be set up (SETUP). Instead, a 304 (Not Modified)
   response will be returned without any message-body.

   If-Modified-Since  =  "If-Modified-Since" ":" HTTP-date

   An example of the field is:

     If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT

12.24 Last-Modified

   The Last-Modified entity-header field indicates the date and time at
   which the origin server believes the presentation description or
   media stream was last modified. See [H14.29]. For the methods
   DESCRIBE or ANNOUNCE, the header field indicates the last modifica-
   tion date and time of the description, for SETUP that of the media
   stream.

12.25 Location

   See [H14.30].

12.26 Proxy-Authenticate

   See [H14.33].

12.27 Proxy-Require

   The Proxy-Require request-header field is used to indicate proxy-sen- |
   sitive features that MUST be supported by the proxy. Any Proxy-       |
   Require header features that are not supported by the proxy MUST be   |
   negatively acknowledged by the proxy to the client using the Unsup-   |
   ported header. Servers should treat this field identically to the     |
   Require field, i.e. the value is syntactically invalid.

   Blocksize Proxy-Require requirements does also apply to |
   the server.                                                           |

   See Section 12.32 for more details on the mechanics of this message   |
   and a usage example.                                                  |

        Proxy-Require  =  "Blocksize"  "Proxy-Require" ":" 1*DIGIT

12.9 Cache-Control 1#option-tag                  ||

   Example of use:                                                       |

      Proxy-Require: con.non-persistent, record.basic                    |

12.28 Public

   The Cache-Control general-header Public response-header field is used to specify directives
   that MUST be obeyed by all caching mechanisms along lists the
   request/response chain.

   Cache directives must be passed through set of methods supported
   by a proxy or gateway appli-
   cation, regardless the server. The purpose of their significance this field is strictly to that application, since inform the directives
   recipient of the capabilities of the server regarding unusual meth-
   ods. The methods listed may or may not be applicable to all recipients along the
   request/response chain. It is not possible Request-
   URI; the Allow header field (section 14.7) MAY be used to specify a cache-direc-
   tive indicate
   methods allowed for a specific cache.

   Cache-Control should particular URI.

        Public  =  "Public" ":" 1#method

   Example of use:

      Public: OPTIONS, SETUP, PLAY, PAUSE, TEARDOWN

   This header field applies only to the server directly connected to
   the client (i.e., the nearest neighbor in a chain of connections).
   If the response passes through a proxy, the proxy MUST either remove
   the Public header field or replace it with one applicable to its own
   capabilities.

12.29 Range

   The Range request and response header field specifies a range of
   time. The range can be specified in a SETUP request number of units.  This specifi-
   cation defines the smpte (Section 3.4), npt (Section 3.5), and its
   response. Note: Cache-Control does clock
   (Section 3.6) range units. Within RTSP, byte ranges [H14.35.1] are
   not govern meaningful and MUST NOT be used. The header may also contain a
   time parameter in UTC, specifying the caching time at which the operation is
   to be made effective. Servers supporting the Range header MUST under-
   stand the NPT range format and SHOULD understand the SMPTE range for-
   mat. The Range response header indicates what range of
   responses as for HTTP, time is actu-
   ally being played or recorded. If the Range header is given in a time
   format that is not understood, the recipient should return 501 (Not
   Implemented).

   Ranges are half-open intervals, including the lower point, but rather of
   excluding the stream identified by upper point. In other words, a range of a-b starts
   exactly at time a, but stops just before b. Only the
   SETUP request. Responses to RTSP requests start time of a
   media unit such as a video or audio frame is relevant. As an example,
   assume that video frames are not cacheable, except
   for responses to DESCRIBE.

   Cache-Control             =  "Cache-Control" ":" 1#cache-directive
   cache-directive           =  cache-request-directive
                            |   cache-response-directive
   cache-request-directive   =  "no-cache"
                            |   "max-stale"
                            |   "min-fresh"
                            |   "only-if-cached"
                            |   cache-extension
   cache-response-directive  =  "public"
                            |   "private"
                            |   "no-cache"
                            |   "no-transform"
                            |   "must-revalidate"
                            |   "proxy-revalidate"
                            |   "max-age" "=" delta-seconds
                            |   cache-extension
   cache-extension generated every 40 ms. A range of
   10.0-10.1 would include a video frame starting at 10.0 or later time
   and would include a video frame starting at 10.08, even though it
   lasted beyond the interval. A range of 10.0-10.08, on the other hand,
   would exclude the frame at 10.08.

   Range             =  token  "Range" ":" 1#ranges-specifier [ ";" "time" "=" ( token | quoted-string ) utc-time ]

     no-cache: Indicates
   ranges-specifier  =  npt-range / utc-range / smpte-range

   Example:

     Range: clock=19960213T143205Z-;time=19970123T143720Z

     The notation is similar to that used for the media stream MUST NOT be cached any-
          where. This HTTP/1.1 [26]
     byte-range header. It allows an origin server clients to prevent caching even by
          caches that have been configured select an excerpt from
     the media object, and to return stale responses play from a given point to
          client requests.

     public: Indicates that the media stream is cacheable by any cache.

     private: Indicates that end as
     well as from the media stream is intended for current location to a single
          user and MUST NOT given point. The start
     of playback can be cached by a shared cache. A private (non-
          shared) cache may cache scheduled for any time in the media stream.

     no-transform: An intermediate cache (proxy) future,
     although a server may find it useful refuse to
          convert the media type of a certain stream. A proxy might, keep server resources for
          example, convert between video formats
     extended idle periods.

12.30 Referer

   See [H14.36]. The URL refers to save cache space or that of the presentation description,
   typically retrieved via HTTP.

12.31 Retry-After

   See [H14.37].

12.32 Require

   The Require request-header field is used by clients to reduce query the amount of traffic on a slow link. Serious opera-
          tional problems      |
   server about options that it may occur, however, when these transformations
          have been applied or may not support. The server MUST  |
   respond to streams intended for certain kinds of
          applications. For example, applications for medical imaging,
          scientific data analysis and those this header by using end-to-end authenti-
          cation all depend on receiving a stream that the Unsupported header to negatively  |
   acknowledge those options which are NOT supported. The response SHALL |
   use the error code 551 (Option Not Supported)

     This is bit-for-bit
          identical to make sure that the original entity-body. Therefore, client-server interaction will
     proceed without delay when all options are understood by both
     sides, and only slow down if options are not understood (as in
     the case above).  For a
          response includes well-matched client-server pair, the no-transform directive, an intermediate
          cache or proxy MUST NOT change
     interaction proceeds quickly, saving a round-trip often
     required by negotiation mechanisms. In addition, it also
     removes state ambiguity when the encoding of client requires features that
     the stream.
          Unlike HTTP, RTSP server does not provide for partial transformation
          at this point, e.g., allowing translation into a different
          language.

     only-if-cached: understand.

   Require  =  "Require" ":" 1#option-tag

   Example:

   C->S:   SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0
           CSeq: 302
           Require: funky-feature
           Funky-Parameter: funkystuff

   S->C:   RTSP/1.0 551 Option not supported
           CSeq: 302
           Unsupported: funky-feature

   C->S:   SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0
           CSeq: 303

   S->C:   RTSP/1.0 200 OK
           CSeq: 303

   In some cases, such as times of extremely poor net-
          work connectivity, a client may want a cache this example, "funky-feature" is the feature tag which indicates
   to return only
          those media streams the client that it currently has stored, the fictional Funky-Parameter field is required.
   The relationship between "funky-feature" and Funky-Parameter is not
   communicated via the RTSP exchange, since that relationship is an
   immutable property of "funky-feature" and thus should not be trans-
   mitted with every exchange.

   Proxies and other intermediary devices SHOULD ignore features that
   are not to
          receive these from the origin server. To do this, the client
          may include the only-if-cached directive understood in a request. If it
          receives this directive, a cache SHOULD either respond using field. If a
          cached media stream particular extension requires
   that is consistent with intermediate devices support it, the other con-
          straints of extension should be tagged
   in the request, or respond with a 504 (Gateway Time-
          out) status. However, if a group of caches Proxy-Require field instead (see Section 12.27).

12.33 RTP-Info

   The RTP-Info response-header field is being operated used to set RTP-specific param-
   eters in the PLAY response. For streams using RTP as a unified system with good internal connectivity, such a
          request MAY transport proto-
   col the RTP-Info header SHALL be forwarded within that group part of caches.

     max-stale: a 200 response to PLAY.

     url: Indicates that the client is willing to accept a media stream that has exceeded its expiration time. If max-stale is
          assigned a value, then URL which for which the client is willing to accept a
          response that has exceeded its expiration time by no more than following RTP
          parameters correspond.

     seq: Indicates the specified sequence number of seconds. If no value is assigned to
          max-stale, then the first packet of the
          stream. This allows clients to gracefully deal with packets
          when seeking. The client is willing uses this value to accept a stale
          response of any age.

     min-fresh: Indicates differentiate
          packets that originated before the client is willing seek from packets that
          originated after the seek.

     rtptime: Indicates the RTP timestamp corresponding to accept a media
          stream whose freshness lifetime is no less than its current
          age plus the specified time
          value in seconds. That is, the client
          wants a Range response that will still be fresh header. (Note: For aggregate con-
          trol, a particular stream may not actually generate a packet
          for at least the
          specified Range time value returned or implied. Thus, there is
          no guarantee that the packet with the sequence number of seconds.

     must-revalidate: When indi-
          cated by seq actually has the must-revalidate directive is present in a
          SETUP response received timestamp indicated by rtptime.)
          The client uses this value to calculate the mapping of RTP
          time to NPT.

          A mapping from RTP timestamps to NTP timestamps (wall
          clock) is available via RTCP. However, this information
          is not sufficient to generate a cache, mapping from RTP times-
          tamps to NPT. Furthermore, in order to ensure that cache MUST NOT use this
          information is available at the entry necessary time (immedi-
          ately at startup or after it becomes stale to respond to a subsequent
          request without first revalidating seek), and that it with the origin server.
          That is, is deliv-
          ered reliably, this mapping is placed in the cache must RTSP control
          channel.

          In order to compensate for drift for long, uninterrupted pre-
          sentations, RTSP clients should additionally map NPT to NTP,
          using initial RTCP sender reports to do an end-to-end revalidation every
          time, if, based solely on the origin server's Expires, mapping, and later
          reports to check drift against the mapping.

   Syntax:

   RTP-Info        =  "RTP-Info" ":" 1#rtsp-info-spec
   rtsp-info-spec  =  stream-url 1*parameter
   stream-url      =  quoted-url / unquoted-url
   unquoted-url    =  "url" "=" safe-url
                  /   ";" "mode" = <"> 1#Method <">
   quoted-url      =  "url" "=" <"> needquote-url <">
   safe-url        =  url
   needquote-url   =  url //That contains ; or ,
   url             =  ( absoluteURI / relativeURI )
   parameter       =  ";" "seq" "=" 1*DIGIT
                  /   ";" "rtptime" "=" 1*DIGIT

   Additional constraint: safe-url MUST NOT contain the
          cached response is stale.)

12.10 Connection

   See [H14.10]

12.11 Content-Base semicolon (";")
   or comma (",") characters. The Content-Base entity-header field may quoted-url form SHOULD only be used to specify the base
   URI for resolving relative URLs within
   when a URL does not meet the entity. This header field
   is described as Base safe-url constraint, in RFC 1808, which is expected order to be revised.

   Content-Base  =  "Content-Base" ":" ensure
   compatibility with implementations conformant to RFC 2326 [21].

   absoluteURI

   If no Content-Base field is present, the base URI of an entity is and relativeURI are defined either by its Content-Location (if that Content-Location URI
   is an absolute URI) in RFC 2396 [22] with RFC
   2732 [30] applied.

   Example:

   RTP-Info: url=rtsp://foo.com/bar.avi/streamid=0;seq=45102,
             url=rtsp://foo.com/bar.avi/streamid=1;seq=30211

12.34 Scale

   A scale value of 1 indicates normal play or record at the URI used normal for-
   ward viewing rate. If not 1, the value corresponds to initiate the request, in that
   order rate with
   respect to normal viewing rate. For example, a ratio of precedence. Note, however, that 2 indicates
   twice the base URI normal viewing rate ("fast forward") and a ratio of 0.5
   indicates half the contents
   within the entity-body may be redefined within that entity-body.

12.12 Content-Encoding

   See [H14.11]

12.13 Content-Language

   See [H14.12]

12.14 Content-Length

   The Content-Length general-header field contains the length normal viewing rate. In other words, a ratio of 2
   has normal play time increase at twice the
   content wallclock rate. For every
   second of elapsed (wallclock) time, 2 seconds of the method (i.e. after the double CRLF following the last
   header). Unlike HTTP, it MUST be included in all messages that carry content beyond will be
   delivered.  A negative value indicates reverse direction.

   Unless requested otherwise by the header portion of Speed parameter, the message. If it is missing, a
   default value data rate
   SHOULD not be changed. Implementation of zero is assumed. It is interpreted according to
   [H14.13].

12.15 Content-Location

   See [H14.14]

12.16 Content-Type

   See [H14.17]. Note that scale changes depends on the content types suitable for RTSP are
   likely to be restricted in practice to presentation descriptions
   server and
   parameter-value types.

12.17 CSeq

   The CSeq general-header field specifies the sequence number media type. For video, a server may, for an
   RTSP request-response pair. This field MUST be present in all
   requests and responses. example, deliver
   only key frames or selected key frames. For every RTSP request containing audio, it may time-scale
   the given
   sequence number, audio while preserving pitch or, less desirably, deliver frag-
   ments of audio.

   The server should try to approximate the corresponding response will have viewing rate, but may
   restrict the same num-
   ber. Any retransmitted request must range of scale values that it supports. The response
   MUST contain the same sequence number
   as actual scale value chosen by the original (i.e. server.  If the sequence number is     |
   server does not incremented for
   retransmissions of the same request).

   CSeq  =  "Cseq" ":" 1*DIGIT

12.18 Date

   See [H14.18].

12.19 Expires

   The Expires entity-header field gives a date and time after which the
   description or media-stream should be considered stale. The interpre-
   tation depends on the method:

     DESCRIBE response: The Expires header indicates a date and time
          after which implement the description should be considered stale.

   A stale cache entry may possibility to scale, it will not normally be returned by a cache (either       |
   return a
   proxy cache Scale header. A server supporting Scale operations for PLAY  |
   or an user agent cache) unless it is first validated RECORDSHALL indicate this with the origin server (or with an intermediate cache that has a fresh
   copy use of the entity). See section 13 for further discussion "play.scale" or      |
   "record.scale" option tags.

   Scale  =  "Scale" ":" [ "-" ] 1*DIGIT [ "." *DIGIT ]

   Example of the
   expiration model. playing in reverse at 3.5 times normal rate:

     Scale: -3.5

12.35 Speed

   The presence of an Expires Speed request-header field does not imply that requests the original
   resource will change or cease server to exist at, before, or after that
   time.

   The format is an absolute date deliver data to
   the client at a particular speed, contingent on the server's ability
   and time as defined desire to serve the media stream at the given speed.  Implementa-
   tion by HTTP-date in
   [H3.3]; it MUST be in RFC1123-date format:

   Expires  =  "Expires" ":" HTTP-date

   An example of its use the server is

     Expires: Thu, 01 Dec 1994 16:00:00 GMT

   RTSP/1.0 clients and caches MUST treat other invalid date formats,
   especially including OPTIONAL. The default is the bit rate of the
   stream.

   The parameter value "0", is expressed as having occurred in the past
   (i.e., already expired).

   To mark a response as "already expired," an origin server should use
   an Expires date decimal ratio, e.g., a value of |
   2.0 indicates that data is equal to the Date header value. To mark a
   response be delivered twice as "never expires," an origin server should use an Expires
   date approximately one year from the time the response fast as normal. A |
   speed of zero is sent.

   RTSP/1.0 servers should invalid. All speeds may not send Expires dates more than one year be possible to support.  |
   Therefore the actual used speed MUST be included in the future. response.     |
   The presence lack of an Expires header field with a date value response header is indication of some
   time in lack of support from   |
   the future on a media stream that otherwise would by default
   be non-cacheable indicates that server of this functionality. Support of the media stream is cacheable, unless speed functionality  |
   are indicated otherwise by a Cache-Control header field (Section 12.9).

12.20 From

   See [H14.22].

12.21 Host

   The Host HTTP request header the "play.speed" option tag.

   Speed = "Speed" ":" 1*DIGIT [ "." *DIGIT ]

   Example:

     Speed: 2.5

   Use of this field [H14.23] is not needed changes the bandwidth used for RTSP. data delivery. It is |
   meant for use in specific circumstances where preview of the presen-  |
   tation at a higher or lower rate is necessary. Implementors should    |
   keep in mind that bandwidth for the session may be silently ignored if sent.

12.22 If-Match

   See [H14.24].

   The If-Match request-header field negotiated before- |
   hand (by means other than RTSP), and therefore re-negotiation may be  |
   necessary. When data is especially useful for ensuring delivered over UDP, it is highly recommended  |
   that means such as RTCP be used to track packet loss rates. If the integrity    |
   data transport is performed over public best-effort networks the      |
   sender is responsible for performing congestion control of the presentation description,        |
   stream. This MAY result in both that the case where
   it communicated speed is fetched via means external impossible  |
   to RTSP (such as HTTP), or in the
   case where maintain.

12.36 Server

   See [H14.38], however the server implementation header syntax is guaranteeing the integrity of
   the description between the time of the DESCRIBE message here corrected.            |

   Server  =  "Server" ":" ( product / comment ) *(SP(product / comment))   ||

12.37 Session

   The Session request-header and response-header field identifies an
   RTSP session started by the media server in a SETUP message.

   The identifier is an opaque identifier, response and thus is not specific to
   any particular session description language.

12.23 If-Modified-Since con-
   cluded by TEARDOWN on the presentation URL. The If-Modified-Since request-header field session identifier is used with
   chosen by the DESCRIBE media server (see Section 3.3) and SETUP methods to make them conditional. If the requested variant
   has not been modified since the time specified in this field, a
   description will not MUST be returned from in
   the server (DESCRIBE) or SETUP response. Once a
   stream will not be set up (SETUP). Instead, client receives a 304 (Not Modified)
   response will be returned without Session identifier, it
   MUST return it for any message-body.

   If-Modified-Since request related to that session.

   Session  =  "If-Modified-Since"  "Session" ":" HTTP-date

   An example of the field is:

     If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT

12.24 Last-Modified session-id [ ";" "timeout" "=" delta-seconds ]

   The timeout parameter is only allowed in a response header.  The Last-Modified entity-header field indicates the date and time at
   which the origin
   server believes uses it to indicate to the presentation description or
   media stream was last modified. See [H14.29]. For client how long the methods
   DESCRIBE server is pre-
   pared to wait between RTSP commands or ANNOUNCE, the header field indicates the last modifica-
   tion date and time other signs of life before
   closing the description, for SETUP that session due to lack of the media
   stream.

12.25 Location

   See [H14.30].

12.26 Proxy-Authenticate

   See [H14.33].

12.27 Proxy-Require activity (see Section A).  The Proxy-Require request-header field
   timeout is used to indicate proxy-sen-
   sitive features that MUST be supported by measured in seconds, with a default of 60 seconds (1
   minute).

   The mechanisms for showing liveness of the proxy. Any Proxy-
   Require header features client is, any RTSP mes-
   sage with a Session header, or a RTCP message. It is RECOMMENDED that are
   a client does not supported by wait to the proxy MUST be
   negatively acknowledged by last second of the proxy timeout before try-
   ing to send a liveness message. Even for RTSP messages using reliable
   protocols, such as TCP, the client if not supported.
   Servers should treat this field identically message may take some time to arrive
   safely at the Require field.

   See Section 12.32 for more details on receiver. To show liveness between RTSP request with
   other effects, the mechanics following mechanisms can be used, in descending
   order of this message preference:

     RTCP: Is used to report transport statistics and a usage example.

12.28 Public SHALL also work as
          keep alive. The Public response-header field lists server can determine the set of methods supported client by used net-
          work address and port together with the server. The purpose of this field is strictly to inform fact that the
   recipient of client
          is reporting on the capabilities servers SSRC(s). A downside of the server regarding unusual meth-
   ods. The methods listed may or may not be applicable using RTCP
          is that it gives lower statistical guarantees to reach the Request-
   URI; the Allow header field (section 14.7) MAY
          server. However that probability is so little that it can be used to indicate
   methods allowed for
          ignored in most cases. For example, a particular URI.

        Public  =  "Public" ":" 1#method

   Example of use:

      Public: OPTIONS, MGET, MHEAD, GET, HEAD

   This header field applies only session with 60 seconds
          timeout and enough bitrate assigned to the server directly connected to RTCP messages, so
          the client (i.e., the nearest neighbor in sends a chain of connections).

   If message on average every 5 seconds.  That
          session have for a network with 5 % packet loss the response passes through probabil-
          ity to not get a proxy, liveness sign over to the proxy MUST either remove server in the Public header field or replace it time-
          out interval is 2.4*E-16. In sessions with one applicable to its own
   capabilities.

12.29 Range

   The Range request and response header field specifies a range shorter timeout
          times, or much higher packet loss, or small RTCP bandwidths
          SHOULD use any of
   time. the mechanisms below.

     PING: The range can be specified in a number use of units.  This specifi-
   cation defines the smpte (Section 3.4), npt (Section 3.5), and clock
   (Section 3.6) range units. Within RTSP, byte ranges [H14.35.1] are
   not meaningful and MUST NOT PING method is the best of the RTSP based
          methods.  It has no other effects than updating the timeout
          timer. In that way it will be used. a minimal message, that also
          does not cause any extra processing for the server. The header down-
          side is that it may also contain not be implemented. A client SHOULD use a
   time parameter in UTC, specifying
          OPTIONS request to verify support of the time PING at which the operation server.
          It is possible to detect support by sending a PING to be made effective. Servers supporting the Range header MUST under-
   stand the NPT range format and SHOULD understand the SMPTE range for-
   mat. The Range response header indicates what range of time is actu-
   ally being played or recorded.
          server. If a 200 (OK) message is received the Range header server supports
          it. In case a 501 (Not Implemented) is given received it does not
          support PING and there is no meaning in continue trying. Also
          the reception of a time
   format error message will also mean that the live-
          ness timer is not understood, the recipient should return 501 (Not
   Implemented).

   Ranges are half-open intervals, including the lower point, but
   excluding updated.

     SET_PARAMETER: When using SET_PARAMETER for keep alive, no body
          SHOULD be included. This method is basically as good as PING,
          however the upper point. In other words, a range implementation support of a-b starts
   exactly at time a, but stops just before b. Only the start time of a
   media unit such as a video or audio frame method is relevant. As an example,
   assume that video frames are generated every 40 ms. A range today lim-
          ited. The same considerations as for PING apply regarding
          checking of
   10.0-10.1 would include a video frame starting at 10.0 or later time support in server and would include a video frame starting at 10.08, even though proxies.

     OPTIONS: This method does also work. However it
   lasted beyond the interval. A range of 10.0-10.08, on causes the other hand,
   would exclude server
          to perform unnecessary processing and result in bigger
          responses than necessary for the frame at 10.08.

   Range             =  "Range" ":" 1#ranges-specifier [ ";" "time" "=" utc-time ]
   ranges-specifier  =  npt-range | utc-range | smpte-range

   Example:

     Range: clock=19960213T143205Z-;time=19970123T143720Z task. The notation reason for this is similar to
          that used for the HTTP/1.1 [26]
     byte-range header. It allows clients to select Public is always included creating overhead.

   Note that a session identifier identifies an excerpt from
     the media object, and to play from RTSP session across
   transport sessions or connections. Control messages for more than one
   RTSP URL may be sent within a given point to single RTSP session. Hence, it is pos-
   sible that clients use the end same session for controlling many streams
   constituting a presentation, as
     well long as all the streams come from the current location to a given point. The start
     of playback can be scheduled for any time
   same server. (See example in the future,
     although a server may refuse to keep server resources Section 14). However, multiple "user"
   sessions for
     extended idle periods.

12.30 Referer

   See [H14.36]. The the same URL refers to that of from the presentation description,
   typically retrieved via HTTP.

12.31 Retry-After

   See [H14.37].

12.32 Require same client MUST use different
   session identifiers.

     The Require request-header field session identifier is used by clients needed to query distinguish several deliv-
     ery requests for the
   server about options that it may or may not support. The server MUST
   respond to this header by using same URL coming from the Unsupported header to negatively
   acknowledge those options which are NOT supported.

     This same client.

   The response 454 (Session Not Found) is to make sure that returned if the client-server interaction will
     proceed without delay when session iden-
   tifier is invalid.

12.38 Supported                                                          |

   The Supported header field enumerates all options are understood the extensions supported by both
     sides, and only slow down if options are not understood (as in |
   the case above).  For client or server. When offered in a well-matched client-server pair, request, the
     interaction proceeds quickly, saving receiver MUST    |
   respond with its corresponding Supported header.                      |

   The Supported header field contains a round-trip often
     required list of option tags, described  |
   in Section 3.7, that are understood by negotiation mechanisms. In addition, it also
     removes state ambiguity when the client requires features that
     the server does not understand.

   Require  =  "Require" ":" 1#option-tag or server.          |

   Example:                                                              |

   optioSupported to=en"Supported" ":" [option-tag *("," option-tag)]       ||
   C->S:   SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0
           CSeq: 302
           Require: funky-feature
           Funky-Parameter: funkystuff

   S->C:   RTSP/1.0 551 Option not supported
           CSeq: 302
           Unsupported: funky-feature

   C->S:   SETUP rtsp://server.com/foo/bar/baz.rm          OPTIONS rtsp://example.com/ RTSP/1.0
           CSeq: 303                      ||
                  Supported: foo, bar, blech                                ||
   S->C:          RTSP/1.0 200 OK
           CSeq: 303
   In this example, "funky-feature" is                                           ||
                  Supported: bar, blech, baz                                ||

12.39 Timestamp

   The Timestamp general-header field describes when the feature tag which indicates client sent the |
   request to the server. The value of the timestamp is of significance  |
   only to the client and may use any timescale. The server MUST echo    |
   the exact same value and MAY, if it has accurate information about    |
   this, add a floating point number indicating the number of seconds    |
   that has elapsed since it has received the fictional Funky-Parameter field request. The timestamp is required.  |
   used by the client to compute the round-trip time to the server so    |
   that it can adjust the timeout value for retransmissions. It also     |
   resolves retransmission ambiguities for unreliable transport of RTSP.

   Timestamp  =  "Timestamp" ":" *(DIGIT) [ "." *(DIGIT) ] [ delay ]
   delay      =  *(DIGIT) [ "." *(DIGIT) ]

12.40 Transport

   The relationship between "funky-feature" Transport request- and Funky-Parameter is not
   communicated via the RTSP exchange, since that relationship response- header field indicates which     |
   transport protocol is an
   immutable property of "funky-feature" and thus should not to be trans-
   mitted with every exchange.

   Proxies used and other intermediary devices SHOULD ignore features that
   are configures its parameters such   |
   as destination address, compression, multicast time-to-live and des-  |
   tination port for a single stream. It sets those values not understood in this field. If already   |
   determined by a particular extension requires
   that intermediate devices support it, the extension should be tagged presentation description.

   Transports are comma separated, listed in the Proxy-Require field instead (see Section 12.27).

12.33 RTP-Info order of preference.
   Parameters may be added to each transport, separated by a semicolon.

   The RTP-Info response-header Transport header field is MAY also be used to set RTP-specific param-
   eters in the PLAY response.

     url: Indicates the stream URL which for which the following RTP change certain trans-
   port parameters. A server MAY refuse to change parameters correspond.

     seq: Indicates the sequence number of the first packet of the an
   existing stream. This allows clients to gracefully deal with packets
          when seeking.

   The client uses this value to differentiate
          packets that originated before the seek from packets that
          originated after the seek.

     rtptime: Indicates the RTP timestamp corresponding to the time
          value server MAY return a Transport response-header field in the Range
   response header. (Note: For aggregate con-
          trol, a particular stream may not to indicate the values actually generate chosen.

   A Transport request header field MAY contain a packet
          for list of transport      |
   options acceptable to the Range time value returned or implied. Thus, there is
          no guarantee client, in the form of multiple transport-  |
   spec entries. In that case, the packet with server MUST return the sequence number indi-
          cated by seq single option  |
   (transport-spec) which was actually has chosen.                           |

   A transport-spec transport option may only contain one of any given   |
   parameter within it. Parameters may be given in any order.  Addition- |
   ally, it may only contain the timestamp indicated by rtptime.) unicast or multicast transport          |
   parameter.

     The client uses this value to calculate the mapping of RTP
          time to NPT.

          A mapping from RTP timestamps to NTP timestamps (wall
          clock) is available via RTCP. However, this information Transport header field is not sufficient restricted to generate describing a mapping from sin-
     gle RTP times-
          tamps to NPT. Furthermore, in order to ensure that this
          information is available at the necessary time (immedi-
          ately at startup or after stream. (RTSP can also control multiple streams as a seek), and that
     single entity.) Making it is deliv-
          ered reliably, this mapping is placed in the part of RTSP control
          channel.

          In order to compensate rather than relying on
     a multitude of session description formats greatly simplifies
     designs of firewalls.

   The syntax for drift the transport specifier is

   transport/profile/lower-transport.

   The default value for long, uninterrupted pre-
          sentations, RTSP clients should additionally map NPT to NTP,
          using initial RTCP sender reports the "lower-transport" parameters is specific to do
   the mapping, profile. For RTP/AVP, the default is UDP.

   Below are the configuration parameters associated with transport:

   General parameters:

     unicast / multicast: This parameter is a mutually exclusive indica-
          tion of whether unicast or multicast delivery will be
          attempted. One of the two values MUST be specified. Clients
          that are capable of handling both unicast and later
          reports multicast trans-
          mission MUST indicate such capability by including two full
          transport-specs with separate parameters for each.

     destination: The address to check drift against the mapping.

   Syntax:

   RTP-Info        =  "RTP-Info" ":" 1#rtsp-info-spec
   rtsp-info-spec  =  stream-url 1*parameter
   stream-url      =  quoted-url which a stream will be sent.  The       | unquoted-url
   unquoted-url    =  "url" "=" safe-url
          client may specify the destination address with the destina-   |   ";" "mode" = <"> 1#Method <">
   quoted-url      =  "url" "=" <"> needquote-url <">
   safe-url        =  url
   needquote-url   =  url
   url             =  ( absoluteURI
          tion parameter. To avoid becoming the unwitting perpetrator of | relativeURI )
   parameter       =  ";" "seq" "=" 1*DIGIT
          a remote-controlled denial-of-service attack, a server SHOULD  |   ";" "rtptime" "=" 1*DIGIT

   Additional constraint: safe-url MUST NOT contain
          authenticate the semicolon (";")
   or comma (",") characters. The quoted-url form client and SHOULD only be used
   when log such attempts before    |
          allowing the client to direct a URL does media stream to an address not meet |
          chosen by the safe-url constraint, in order to ensure
   compatibility with server. This is particularly important if RTSP   |
          commands are issued via UDP, but implementations conformant cannot rely   |
          on TCP as reliable means of client identification by itself.   |
          IPv6 addresses is RECOMMENDED to be given as fully qualified   |
          domain to make it backwards compatible with RFC 2326 [21].

   absoluteURI and relativeURI are defined implemen- |
          tations.                                                       |

     source: If the source address for the stream is different than can  |
          be derived from the RTSP endpoint address (the server in RFC 2396 [22].

   Example:

   RTP-Info: url=rtsp://foo.com/bar.avi/streamid=0;seq=45102,
             url=rtsp://foo.com/bar.avi/streamid=1;seq=30211

12.34 Scale

   A scale value of 1 indicates normal play play- |
          back or record at the normal for-
   ward viewing rate. If not 1, the value corresponds to client in recording), the rate source address SHOULD be |
          specified. To maintain backwards compatibility with
   respect to normal viewing rate. For example, RFC 2326,  |
          any IPv6 host's address must be given as a ratio of 2 indicates
   twice the normal viewing rate ("fast forward") and fully qualified     |
          domain name.

          This information may also be available through SDP.  How-
          ever, since this is more a ratio feature of 0.5
   indicates half transport than
          media initialization, the normal viewing rate. In other words, a ratio of 2
   has normal play time increase at twice authoritative source for this
          information should be in the wallclock rate. For every
   second of elapsed (wallclock) time, 2 seconds SETUP response.

     layers: The number of content will multicast layers to be
   delivered.  A negative value indicates reverse direction.

   Unless requested otherwise by used for this media
          stream. The layers are sent to consecutive addresses starting
          at the Speed parameter, destination address.

     mode: The mode parameter indicates the data rate
   SHOULD not methods to be changed. Implementation of scale changes depends on the
   server and media type. For video, a server may, supported for example, deliver
   only key frames or selected key frames. For audio, it may time-scale
          this session. Valid values are PLAY and RECORD. If not pro-
          vided, the audio while preserving pitch or, less desirably, deliver frag-
   ments of audio.

   The server default is PLAY.

     append: If the mode parameter includes RECORD, the append parameter
          indicates that the media data should try append to approximate the viewing rate, but may
   restrict existing
          resource rather than overwrite it.  If appending is requested
          and the range of scale values that server does not support this, it supports. The response MUST contain refuse the actual scale value chosen
          request rather than overwrite the resource identified by the server.

   If
          URI. The append parameter is ignored if the request contains a Range parameter, mode parameter
          does not contain RECORD.                                       |

     interleaved: The interleaved parameter implies mixing the new scale value will
   take effect at that time.

   Scale  =  "Scale" ":" [ "-" ] 1*DIGIT [ "." *DIGIT ]

   Example of playing media     |
          stream with the control stream in reverse at 3.5 times normal rate:

     Scale: -3.5

12.35 Speed whatever protocol is being   |
          used by the control stream, using the mechanism defined in     |
          Section 10.13. The Speed request-header field requests argument provides the server to deliver data channel number to be  |
          used in the client at $ statement and MUST be present. This parameter    |
          MAY be specified as a particular speed, contingent on range, e.g., interleaved=4-5 in cases    |
          where the server's ability
   and desire to serve transport choice for the media stream at the given speed.  Implementa-
   tion by requires it,   |
          e.g.  for RTP with RTCP.

          This allows RTP/RTCP to be handled similarly to the server is OPTIONAL. The default way
          that it is done with UDP, i.e., one channel for RTP and
          the bit rate of the
   stream.

   The other for RTCP.

   Multicast-specific:

     ttl: multicast time-to-live.

   RTP-specific:

     port: This parameter value provides the RTP/RTCP port pair for a multi-
          cast session. It is expressed specified as a decimal ratio, range, e.g., a value of
   2.0 indicates that port=3456-3457

     client_port: This parameter provides the unicast RTP/RTCP port pair
          on the client where media data and control information is to
          be delivered twice as fast as normal. A
   speed of zero sent. It is invalid. If specified as a range, e.g., port=3456-3457
     server_port: This parameter provides the request contains unicast RTP/RTCP port pair
          on the server where media data and control information is to
          be sent. It is specified as a Range parameter, range, e.g., port=3456-3457

     client_rtcp_port: This parameter allows to specify the new speed value client's     |
          RTCP port number individually from the RTP port. This will take effect at that time.

   Speed = "Speed" ":" 1*DIGIT [ "." *DIGIT ]

   Example:

     Speed: 2.5

   Use     |
          allow the usage of NAT traversal techniques like STUN  [31].   |
          However as it introduce after RFC 2326 it may result interop-  |
          erability problems. Before using this field changes parameter the bandwidth used for data delivery. It is
   meant for use in specific circumstances where preview server     |
          MUST signal support of either the presen-
   tation at a higher "play.basic" or lower rate is necessary. Implementors should
   keep in mind that bandwidth for the session may be negotiated before-
   hand (by means other than RTSP), and therefore re-negotiation may be
   necessary. When data is delivered over UDP, it is highly recommended
   that means such as RTCP be used          |
          "record.basic" option tags.                                    |

     client_rtcp_port: This parameter allows to track packet loss rates.

12.36 Server

   See [H14.38]

12.37 Session

   The Session request-header and response-header field identifies an
   RTSP session started by specify the server's     |
          RTCP port number individually from the RTP port. This will     |
          allow the media server usage of NAT traversal techniques like STUN  [31].   |
          However as it introduce after RFC 2326 it may result interop-  |
          erability problems. This parameter MUST only be included in a SETUP response and con-
   cluded by TEARDOWN on  |
          response, when the presentation URL. request's transport header included the     |
          "client_rtcp_port" parameter.                                  |

     ssrc: The session identifier is
   chosen ssrc parameter indicates the RTP SSRC [23] value that     |
          should be (request) or will be (response) used by the media server (see Section 3.3) and MUST    |
          server. This parameter is only valid for unicast transmission. |
          It identifies the synchronization source to be returned in associated with |
          the SETUP response. Once a client receives media stream, and is expressed as an eight digit hexideci- |
          mal value. In cases that a Session identifier, it
   MUST return sender will use multiple SSRC it for any request related to that session.

   Session    |
          SHOULD NOT use this parameter.

   Transport           =  "Session"  "Transport" ":" session-id 1#transport-spec
   transport-spec      =  transport-id *parameter
   transport-id        =  transport-protocol "/" profile ["/" lower-transport]
                          ; no LWS is allowed inside transport-id
   transport-protocol  =  "RTP" / token
   profile             =  "AVP" / token
   lower-transport     =  "TCP" / "UDP" / token
   parameter           =  ";" ( "unicast" / "multicast" )
                      /   ";" "source" "=" address
                      /   ";" "destination" [ "=" address ]
                      /   ";" "timeout" "interleaved" "=" delta-seconds channel [ "-" channel ]

   The timeout parameter is only allowed
                      /   ";" "append"
                      /   ";" "ttl" "=" ttl
                      /   ";" "layers" "=" 1*DIGIT
                      /   ";" "port" "=" port [ "-" port ]
                      /   ";" "client_port" "=" port [ "-" port ]
                      /   ";" "server_port" "=" port [ "-" port ]
                      /   ";" "client_rtcp_port" "=" port
                      /   ";" "server_rtcp_port" "=" port
                      /   ";" "ssrc" "=" ssrc
                      /   ";" "mode" "=" mode-spec
   ttl                 =  1*3(DIGIT)
   port                =  1*5(DIGIT)
   ssrc                =  8*8(HEX)
   channel             =  1*3(DIGIT)
   address             =  host ;As defined in RFC 2732 [30]
   mode-spec           =  <"> 1#mode <"> / mode
   mode                =  "PLAY" / "RECORD" / token

   Below is a usage example, showing a response header.  The
   server uses it to indicate to the client how long the server is pre-
   pared to wait between RTSP commands before closing advertising the session due capability
   to
   lack of activity (see Section A). The timeout is measured in seconds,
   with a default of 60 seconds (1 minute).

   Note that a session identifier identifies an RTSP session across
   transport sessions handle multicast or connections. Control messages for more than one
   RTSP URL may be sent within a single RTSP session. Hence, it unicast, preferring multicast. Since this is pos-
   sible that clients use the same session for controlling many streams
   constituting a presentation, as long as all
   unicast-only stream, the streams come from server responds with the
   same server. (See example in Section 14). However, multiple "user"
   sessions proper transport
   parameters for the same URL from the same client MUST use different
   session identifiers. unicast.

     C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0
           CSeq: 302
           Transport: RTP/AVP;multicast;mode="PLAY",
               RTP/AVP;unicast;client_port=3456-3457;mode="PLAY"

     S->C: RTSP/1.0 200 OK
           CSeq: 302
           Date: 23 Jan 1997 15:35:06 GMT
           Session: 47112344
           Transport: RTP/AVP;unicast;client_port=3456-3457;
               server_port=6256-6257;mode="PLAY"

12.41 Unsupported

   The session identifier is needed to distinguish several deliv-
     ery requests for Unsupported response-header field lists the same URL coming from features not sup-
   ported by the same client.

   The response 454 (Session Not Found) is returned if server. In the session iden-
   tifier is invalid.

12.38 Supported                                                          |

   The Supported header case where the feature was specified via
   the Proxy-Require field enumerates all (Section 12.27), if there is a proxy on the extensions supported by |
   path between the client or server. When offered in a request, and the receiver server, the proxy MUST    |
   respond send a
   response message with its cooresponding Supported header.                      |

   The Supported header field contains a list status code of option tags, described  |
   in 551 (Option Not Supported).
   The request SHALL NOT be forwarded.

   See Section 3.7, that are understood by 12.32 for a usage example.

   Unsupported  =  "Unsupported" ":" 1#option-tag

12.42 User-Agent

   See [H14.43] for explanation, however the client or server. syntax is clarified due to  |
   Example:
   an error in RFC 2616. A Client SHOULD include this header in all RTSP |

   C->S OPTIONS rtsp://example.com/ RTSP/1.0                                ||
   Supported: foo, bar, blech
   messages it sends.                                                    |

   User-Agent           =  "User-Agent" ":" ( product / comment ) 0*(SP     ||

   SuppoS->C:RTSP/1.0e200 OKz
   (product / comment)                                                      ||

12.39 Timestamp

   The Timestamp general-header field describes when the client sent the
   request to

12.43 Vary

   See [H14.44]

12.44 Via

   See [H14.45].

12.45 WWW-Authenticate

   See [H14.47].

13 Caching

   In HTTP, response-request pairs are cached. RTSP differs signifi-
   cantly in that respect. Responses are not cacheable, with the server. The value excep-
   tion of the timestamp is of significance
   only to presentation description returned by DESCRIBE or included
   with ANNOUNCE. (Since the client responses for anything but DESCRIBE and may use
   GET_PARAMETER do not return any timescale. The server MUST echo
   the exact same value and MAY, if it has accurate information about
   this, add a floating point number indicating the number of seconds
   that has elapsed since data, caching is not really an issue
   for these requests.) However, it has received the request. The timestamp is
   used by desirable for the client continuous
   media data, typically delivered out-of-band with respect to compute the round-trip time RTSP, to
   be cached, as well as the server so
   that session description.

   On receiving a SETUP or PLAY request, a proxy ascertains whether it can adjust
   has an up-to-date copy of the timeout value for retransmissions.

   Timestamp  =  "Timestamp" ":" *(DIGIT) [ "." *(DIGIT) ] [ delay ]
   delay      =  *(DIGIT) [ "." *(DIGIT) ]

12.40 Transport

   The Transport request-header field indicates which transport protocol
   is to be used continuous media content and configures its parameters such as destination
   address, compression, multicast time-to-live and destination port for
   a single stream. It sets those values not already determined by a
   presentation
   description.

   Transports are comma separated, listed in order of preference.
   Parameters may be added to each transport, separated It can determine whether the copy is up-to-date by issu-
   ing a semicolon.

   The Transport SETUP or DESCRIBE request, respectively, and comparing the
   Last-Modified header field MAY also be used to change certain trans-
   port parameters. A server MAY refuse to change parameters with that of an
   existing stream.

   The server MAY return a Transport response-header field in the
   response to indicate cached copy. If the values actually chosen.

   A Transport request header field may contain a list of copy is not
   up-to-date, it modifies the SETUP transport
   options acceptable parameters as appropriate
   and forwards the request to the client, in origin server. Subsequent control
   commands such as PLAY or PAUSE then pass the form of multiple transport-
   spec entries. In that case, proxy unmodified. The
   proxy delivers the server MUST return continuous media data to the client, while possi-
   bly making a single option
   (transport-spec) which was actually chosen.

   A transport-spec transport option may only contain one of any given   |
   parameter within it. Parameters may be local copy for later reuse. The exact behavior allowed
   to the cache is given by the cache-response directives described in
   Section 12.9. A cache MUST answer any order.  Addition- |
   ally, DESCRIBE requests if it may only contain the unicast or multicast transport parame-  |
   ter.

     The Transport header field is restricted cur-
   rently serving the stream to describing a sin-
     gle RTP stream. (RTSP can also control multiple streams the requestor, as a
     single entity.) Making it part of RTSP rather than relying on
     a multitude is possible that
   low-level details of session the stream description formats greatly simplifies
     designs of firewalls.

   The syntax for may have changed on the transport specifier is

   transport/profile/lower-transport.

   The default value for
   origin-server.

   Note that an RTSP cache, unlike the "lower-transport" parameters HTTP cache, is specific to of the profile. For RTP/AVP, "cut-
   through" variety. Rather than retrieving the default is UDP.

   Below are whole resource from the configuration parameters associated with transport:

   General parameters:

     unicast | multicast: This parameter is a mutually exclusive indica-
          tion of whether unicast or multicast delivery will be
          attempted. One of
   origin server, the two values MUST be specified. Clients
          that are capable of handling both unicast and multicast trans-
          mission MUST indicate such capability cache simply copies the streaming data as it
   passes by including two full
          transport-specs with separate parameters for each.

     destination: The address on its way to which a stream will be sent.  The       |
          client may specify the destination address with the destina-   |
          tion parameter. client. Thus, it does not introduce addi-
   tional latency.

   To avoid becoming the unwitting perpetrator of |
          a remote-controlled denial-of-service attack, client, an RTSP proxy cache appears like a regular media
   server, to the media origin server SHOULD  |
          authenticate like a client. Just as an HTTP
   cache has to store the client content type, content language, and SHOULD log such attempts before    |
          allowing so on for
   the client to direct objects it caches, a media stream cache has to an address not |
          chosen by store the server. This is particularly important if RTSP   |
          commands presentation
   description.  Typically, a cache eliminates all transport-references
   (that is, multicast information) from the presentation description,
   since these are issued via UDP, but implementations cannot rely   |
          on TCP as reliable means independent of client identification by itself.

     source: If the source address for the stream is different than can
          be derived data delivery from the RTSP endpoint address (the server in play-
          back or cache to
   the client in recording), client.  Information on the source address MAY be
          specified.

          This information may also be available through SDP.  How-
          ever, since this is more a feature of transport than
          media initialization, encodings remains the authoritative source for this
          information should be in same. If the SETUP response.

     layers: The number of multicast layers
   cache is able to be used for this translate the cached media
          stream. data, it would create a
   new presentation description with all the encoding possibilities it
   can offer.

14 Examples

   The layers are sent following examples refer to consecutive addresses starting
          at the destination address.

     mode: stream description formats that are
   not standards, such as RTSL. The mode parameter indicates the methods following examples are not to be supported
   used as a reference for
          this session. Valid values are PLAY those formats.

14.1 Media on Demand (Unicast)

   Client C requests a movie from media servers A (audio.example.com )
   and RECORD. If not pro-
          vided, the default V (video.example.com ). The media description is PLAY.

     append: If stored on a web
   server W. The media description contains descriptions of the mode parameter includes RECORD, presen-
   tation and all its streams, including the append parameter
          indicates codecs that are available,
   dynamic RTP payload types, the media data should append to the existing
          resource rather than overwrite it.  If appending is requested protocol stack, and content informa-
   tion such as language or copyright restrictions. It may also give an
   indication about the server does not support this, it MUST refuse the
          request rather than overwrite timeline of the resource identified by movie.

   In this example, the
          URI. The append parameter client is ignored if only interested in the mode parameter
          does not contain RECORD.

     interleaved: The interleaved parameter implies mixing last part of
   the media
          stream movie.

   C->W: GET /twister.sdp HTTP/1.1
         Host: www.example.com
         Accept: application/sdp

   W->C: HTTP/1.0 200 OK
         Content-Type: application/sdp
         v=0
         o=- 2890844526 2890842807 IN IP4 192.16.24.202
         s=RTSP Session
         m=audio 0 RTP/AVP 0
         a=control:rtsp://audio.example.com/twister/audio.en
         m=video 0 RTP/AVP 31
         a=control:rtsp://video.example.com/twister/video

   C->A: SETUP rtsp://audio.example.com/twister/audio.en RTSP/1.0
         CSeq: 1
         Transport: RTP/AVP/UDP;unicast;client_port=3056-3057

   A->C: RTSP/1.0 200 OK
         CSeq: 1
         Session: 12345678
         Transport: RTP/AVP/UDP;unicast;client_port=3056-3057;
                    server_port=5000-5001

   C->V: SETUP rtsp://video.example.com/twister/video RTSP/1.0
         CSeq: 1
         Transport: RTP/AVP/UDP;unicast;client_port=3058-3059

   V->C: RTSP/1.0 200 OK
         CSeq: 1
         Session: 23456789
         Transport: RTP/AVP/UDP;unicast;client_port=3058-3059;
                    server_port=5002-5003

   C->V: PLAY rtsp://video.example.com/twister/video RTSP/1.0
         CSeq: 2
         Session: 23456789
         Range: smpte=0:10:00-

   V->C: RTSP/1.0 200 OK
         CSeq: 2
         Session: 23456789
         Range: smpte=0:10:00-0:20:00
         RTP-Info: url=rtsp://video.example.com/twister/video;
       seq=12312232;rtptime=78712811

   C->A: PLAY rtsp://audio.example.com/twister/audio.en RTSP/1.0
         CSeq: 2
         Session: 12345678
         Range: smpte=0:10:00-

   A->C: RTSP/1.0 200 OK
         CSeq: 2
         Session: 12345678
         Range: smpte=0:10:00-0:20:00
         RTP-Info: url=rtsp://audio.example.com/twister/audio.en;
       seq=876655;rtptime=1032181

   C->A: TEARDOWN rtsp://audio.example.com/twister/audio.en RTSP/1.0
         CSeq: 3
         Session: 12345678

   A->C: RTSP/1.0 200 OK
         CSeq: 3

   C->V: TEARDOWN rtsp://video.example.com/twister/video RTSP/1.0
         CSeq: 3
         Session: 23456789

   V->C: RTSP/1.0 200 OK
         CSeq: 3

   Even though the audio and video track are on two different servers,
   and may start at slightly different times and may drift with respect
   to each other, the control stream in whatever protocol is being
          used by client can synchronize the control stream, two using the mechanism defined standard RTP
   methods, in
          Section 10.13. The argument provides particular the channel number to be
          used time scale contained in the $ statement. This parameter may be specified as RTCP sender
   reports.

14.2 Streaming of a
          range, e.g., interleaved=4-5 Container file

   For purposes of this example, a container file is a storage entity in cases where the transport
          choice for the
   which multiple continuous media stream requires it.

          This allows RTP/RTCP to be handled similarly types pertaining to the way
          that it is done with UDP, i.e., one channel for RTP and
          the other for RTCP.

   Multicast-specific:

     ttl: multicast time-to-live.

   RTP-specific:

     port: This parameter provides same end-user
   presentation are present. In effect, the RTP/RTCP port pair for a multi-
          cast session. It is specified as container file represents an
   RTSP presentation, with each of its components being RTSP streams.
   Container files are a range, e.g., port=3456-3457

     client_port: This parameter provides the unicast RTP/RTCP port pair
          on widely used means to store such presentations.
   While the client where media data and control information components are transported as independent streams, it is
   desirable to
          be sent. It is specified as maintain a range, e.g., port=3456-3457
     server_port: This parameter provides common context for those streams at the unicast RTP/RTCP port pair
          on
   server end.

     This enables the server where media data and control information is to
          be sent. It is specified as keep a range, e.g., port=3456-3457

     ssrc: The ssrc parameter indicates single storage handle open
     easily. It also allows treating all the RTP SSRC [23] value that
          should be (request) or will be (response) used streams equally in
     case of any prioritization of streams by the media server. This parameter is only valid for unicast transmission.

   It identifies is also possible that the synchronization source presentation author may wish to be associated with prevent
   selective retrieval of the streams by the client in order to preserve
   the artistic effect of the combined media stream, and presentation. Similarly, in
   such a tightly bound presentation, it is expressed as desirable to be able to con-
   trol all the streams via a single control message using an eight digit hexideci-
          mal value.

   Transport           =  "Transport" ":" 1#transport-spec
   transport-spec      =  transport-id *parameter
   transport-id        =  transport-protocol "/" profile ["/" lower-transport]
                          ; no LWS is allowed inside transport-id
   transport-protocol  =  "RTP" | token
   profile             =  "AVP" | token
   lower-transport     =  "TCP" | "UDP" | token
   parameter           =  ";" ( "unicast" | "multicast" )
                      |   ";" "source" [ "=" address ]
                      |   ";" "destination" [ "=" address ]
                      |   ";" "interleaved" "=" channel [ "-" channel ]
                      |   ";" "append"
                      |   ";" "ttl" "=" ttl
                      |   ";" "layers" "=" 1*DIGIT
                      |   ";" "port" "=" port [ "-" port ]
                      |   ";" "client_port" "=" port [ "-" port ]
                      |   ";" "server_port" "=" port [ "-" port ]
                      |   ";" "source" "=" address
                      |   ";" "ssrc" "=" ssrc
                      |   ";" "mode" "=" mode-spec
   ttl                 =  1*3(DIGIT)
   port                =  1*5(DIGIT)
   ssrc                =  8*8(HEX)
   channel             =  1*3(DIGIT)
   address             =  host
   mode-spec           =  <"> 1#mode <"> | mode
   mode                =  "PLAY" | "RECORD" | token

   Below aggregate
   URL.

   The following is an example of using a usage example, showing a client advertising the capability single RTSP session to handle multicast or unicast, preferring multicast. Since this is a
   unicast-only stream, control
   multiple streams. It also illustrates the use of aggregate URLs.

   Client C requests a presentation from media server responds with M. The movie is
   stored in a container file. The client has obtained an RTSP URL to
   the proper transport
   parameters for unicast.

     C->S: container file.

   C->M: DESCRIBE rtsp://foo/twister RTSP/1.0
         CSeq: 1

   M->C: RTSP/1.0 200 OK
         CSeq: 1
         Content-Type: application/sdp
         Content-Length: 164

         v=0
         o=- 2890844256 2890842807 IN IP4 172.16.2.93
         s=RTSP Session
         i=An Example of RTSP Session Usage
         a=control:rtsp://foo/twister
         t=0 0
         m=audio 0 RTP/AVP 0
         a=control:rtsp://foo/twister/audio
         m=video 0 RTP/AVP 26
         a=control:rtsp://foo/twister/video

   C->M: SETUP rtsp://example.com/foo/bar/baz.rm rtsp://foo/twister/audio RTSP/1.0
         CSeq: 2
         Transport: RTP/AVP;unicast;client_port=8000-8001

   M->C: RTSP/1.0 200 OK
         CSeq: 2
         Transport: RTP/AVP;unicast;client_port=8000-8001;
                    server_port=9000-9001
         Session: 12345678

   C->M: SETUP rtsp://foo/twister/video RTSP/1.0
         CSeq: 3
         Transport: RTP/AVP;unicast;client_port=8002-8003
         Session: 12345678

   M->C: RTSP/1.0 200 OK
         CSeq: 3
         Transport: RTP/AVP;unicast;client_port=8002-8003;
                    server_port=9004-9005
         Session: 12345678
   C->M: PLAY rtsp://foo/twister RTSP/1.0
         CSeq: 4
         Range: npt=0-
         Session: 12345678

   M->C: RTSP/1.0 200 OK
         CSeq: 4
         Session: 12345678
         RTP-Info: url=rtsp://foo/twister/video;
       seq=9810092;rtptime=3450012

   C->M: PAUSE rtsp://foo/twister/video RTSP/1.0
         CSeq: 302
           Transport: RTP/AVP;multicast;mode="PLAY",
               RTP/AVP;unicast;client_port=3456-3457;mode="PLAY"

     S->C: 5
         Session: 12345678

   M->C: RTSP/1.0 460 Only aggregate operation allowed
         CSeq: 5

   C->M: PAUSE rtsp://foo/twister RTSP/1.0
         CSeq: 6
         Session: 12345678

   M->C: RTSP/1.0 200 OK
         CSeq: 302
           Date: 23 Jan 1997 15:35:06 GMT 6
         Session: 47112344 12345678

   C->M: SETUP rtsp://foo/twister RTSP/1.0
         CSeq: 7
         Transport: RTP/AVP;unicast;client_port=3456-3457;
               server_port=6256-6257;mode="PLAY"

12.41 Unsupported

   The Unsupported response-header field lists the features RTP/AVP;unicast;client_port=10000

   M->C: RTSP/1.0 459 Aggregate operation not sup-
   ported by the server. allowed
         CSeq: 7

   In the case where the feature was specified via
   the Proxy-Require field (Section 12.32), if there is a proxy on the
   path between first instance of failure, the client and the server, the proxy MUST insert a
   response message with a status code tries to pause one
   stream (in this case video) of 551 (Option Not Supported).

   See Section 12.32 the presentation. This is disallowed
   for a usage example.

   Unsupported  =  "Unsupported" ":" 1#option-tag

12.42 User-Agent

   See [H14.43]

12.43 Vary

   See [H14.44]

12.44 Via

   See [H14.45].

12.45 WWW-Authenticate

   See [H14.47].

13 Caching

   In HTTP, response-request pairs are cached. RTSP differs signifi-
   cantly in that respect. Responses are not cacheable, with the excep-
   tion of the presentation description returned by DESCRIBE or included
   with ANNOUNCE. (Since the responses for anything but DESCRIBE and
   GET_PARAMETER do not return any data, caching is server. In the second instance, the
   aggregate URL may not really an issue be used for these requests.) However, it SETUP and one control message is desirable for the continuous
   media data, typically delivered out-of-band with respect to RTSP,
   required per stream to
   be cached, as well as set up transport parameters.

     This keeps the session description.

   On receiving a SETUP or PLAY request, a proxy ascertains whether it
   has an up-to-date copy syntax of the continuous media content Transport header simple and its
   description. It can determine whether the copy is up-to-date
     allows easy parsing of transport information by issu-
   ing firewalls.

14.3 Single Stream Container Files
   Some RTSP servers may treat all files as though they are "container
   files", yet other servers may not support such a SETUP or DESCRIBE request, respectively, and comparing the
   Last-Modified header with that concept. Because of
   this, clients SHOULD use the cached copy. If the copy is not
   up-to-date, it modifies the SETUP transport parameters as appropriate
   and forwards rules set forth in the session descrip-
   tion for request URLs, rather than assuming that a consistent URL may
   always be used throughout. Here's an example of how a multi-stream
   server might expect a single-stream file to the origin server. Subsequent control
   commands such as be served:

       C->S  DESCRIBE rtsp://foo.com/test.wav RTSP/1.0
             Accept: application/x-rtsp-mh, application/sdp
             CSeq: 1

       S->C  RTSP/1.0 200 OK
             CSeq: 1
             Content-base: rtsp://foo.com/test.wav/
             Content-type: application/sdp
             Content-length: 48

             v=0
             o=- 872653257 872653257 IN IP4 172.16.2.187
             s=mu-law wave file
             i=audio test
             t=0 0
             m=audio 0 RTP/AVP 0
             a=control:streamid=0

       C->S  SETUP rtsp://foo.com/test.wav/streamid=0 RTSP/1.0
             Transport: RTP/AVP/UDP;unicast;
                        client_port=6970-6971;mode="PLAY"
             CSeq: 2

       S->C  RTSP/1.0 200 OK
             Transport: RTP/AVP/UDP;unicast;client_port=6970-6971;
                        server_port=6970-6971;mode="PLAY"
             CSeq: 2
             Session: 2034820394

       C->S  PLAY or PAUSE then pass rtsp://foo.com/test.wav RTSP/1.0
             CSeq: 3
             Session: 2034820394

       S->C  RTSP/1.0 200 OK
             CSeq: 3
             Session: 2034820394
             RTP-Info: url=rtsp://foo.com/test.wav/streamid=0;
               seq=981888;rtptime=3781123
   Note the proxy unmodified. The
   proxy delivers different URL in the continuous media data to SETUP command, and then the client, while possi-
   bly making a local copy for later reuse. The exact behavior allowed switch back
   to the cache is given by the cache-response directives described aggregate URL in
   Section 12.9. A cache MUST answer any DESCRIBE requests if it the PLAY command. This makes complete sense
   when there are multiple streams with aggregate control, but is cur-
   rently serving less
   than intuitive in the stream to special case where the requestor, as number of streams is
   one.

   In this special case, it is possible recommended that
   low-level details servers be forgiving of the stream description may have changed on the
   origin-server.

   Note
   implementations that an RTSP cache, unlike the HTTP cache, is of the "cut-
   through" variety. Rather than retrieving the whole resource from the
   origin server, the cache simply copies the streaming data as it
   passes by on its way to the client. Thus, it does not introduce addi-
   tional latency.

   To the client, an RTSP proxy cache appears like a regular media
   server, to send:

       C->S  PLAY rtsp://foo.com/test.wav/streamid=0 RTSP/1.0
             CSeq: 3

   In the media origin worst case, servers should send back:

       S->C  RTSP/1.0 460 Only aggregate operation allowed
             CSeq: 3

   One would also hope that server like a client. Just as an HTTP
   cache has to store the content type, content language, and so on for
   the objects it caches, a media cache has to store the presentation
   description.  Typically, a cache eliminates all transport-references
   (that is, multicast information) from the presentation description,
   since these implementations are independent also forgiving of
   the data delivery from the cache to
   the client.  Information on the encodings remains the same. If the
   cache following:

       C->S  SETUP rtsp://foo.com/test.wav RTSP/1.0
             Transport: rtp/avp/udp;client_port=6970-6971;mode="PLAY"
             CSeq: 2

   Since there is able to translate the cached media data, it would create only a
   new presentation description with all the encoding possibilities it
   can offer.

14 Examples

   The following examples refer to single stream description formats that are
   not standards, such as RTSL. The following examples are in this file, it's not to be
   used as a reference for those formats.

14.1 ambiguous
   what this means.

14.4 Live Media on Demand (Unicast)
   Client C requests a movie from media servers A (audio.example.com )
   and V (video.example.com ). Presentation Using Multicast

   The media description is stored on a web server W. The media description contains descriptions of M chooses the presen-
   tation multicast address and all its streams, including the codecs port. Here, we
   assume that are available,
   dynamic RTP payload types, the protocol stack, and content informa-
   tion such as language or copyright restrictions. It may also give an
   indication about web server only contains a pointer to the timeline of full
   description, while the movie.

   In this example, media server M maintains the full description.

   C->W: GET /concert.sdp HTTP/1.1
         Host: www.example.com

   W->C: HTTP/1.1 200 OK
         Content-Type: application/x-rtsl
         <session>
           <track src="rtsp://live.example.com/concert/audio">
         </session>

   C->M: DESCRIBE rtsp://live.example.com/concert/audio RTSP/1.0
         CSeq: 1

   M->C: RTSP/1.0 200 OK
         CSeq: 1
         Content-Type: application/sdp
         Content-Length: 44

         v=0
         o=- 2890844526 2890842807 IN IP4 192.16.24.202
         s=RTSP Session
         m=audio 3456 RTP/AVP 0
         c=IN IP4 224.2.0.1/16
         a=control:rtsp://live.example.com/concert/audio

   C->M: SETUP rtsp://live.example.com/concert/audio RTSP/1.0
         CSeq: 2
         Transport: RTP/AVP;multicast

   M->C: RTSP/1.0 200 OK
         CSeq: 2
         Transport: RTP/AVP;multicast;destination=224.2.0.1;
                    port=3456-3457;ttl=16
         Session: 0456804596

   C->M: PLAY rtsp://live.example.com/concert/audio RTSP/1.0
         CSeq: 3
         Session: 0456804596

   M->C: RTSP/1.0 200 OK
         CSeq: 3
         Session: 0456804596

14.5 Recording

   The conference participant client is only interested in C asks the media server M to record
   the last part audio and video portions of a meeting. The client uses the movie.

   C->W: GET /twister.sdp HTTP/1.1
         Host: www.example.com
         Accept: application/sdp

   W->C: HTTP/1.0 200 OK
   ANNOUNCE method to provide meta-information about the recorded ses-
   sion to the server.

   C->M: ANNOUNCE rtsp://server.example.com/meeting RTSP/1.0
         CSeq: 90
         Content-Type: application/sdp
         Content-Length: 121

         v=0
         o=- 2890844526 2890842807
         o=camera1 3080117314 3080118787 IN IP4 192.16.24.202
         s=RTSP Session 195.27.192.36
         s=IETF Meeting, Munich - 1
         i=The thirty-ninth IETF meeting will be held in Munich, Germany
         u=http://www.ietf.org/meetings/Munich.html
         e=IETF Channel 1 <ietf39-mbone@uni-koeln.de>
         p=IETF Channel 1 +49-172-2312 451
         c=IN IP4 224.0.1.11/127
         t=3080271600 3080703600
         a=tool:sdr v2.4a6
         a=type:test
         m=audio 0 21010 RTP/AVP 0
         a=control:rtsp://audio.example.com/twister/audio.en 5
         c=IN IP4 224.0.1.11/127
         a=ptime:40
         m=video 0 61010 RTP/AVP 31
         a=control:rtsp://video.example.com/twister/video

   C->A: SETUP rtsp://audio.example.com/twister/audio.en RTSP/1.0
         CSeq: 1
         Transport: RTP/AVP/UDP;unicast;client_port=3056-3057

   A->C:
         c=IN IP4 224.0.1.12/127

   M->C: RTSP/1.0 200 OK
         CSeq: 1
         Session: 12345678
         Transport: RTP/AVP/UDP;unicast;client_port=3056-3057;
                    server_port=5000-5001

   C->V: 90

   C->M: SETUP rtsp://video.example.com/twister/video rtsp://server.example.com/meeting/audiotrack RTSP/1.0
         CSeq: 1 91
         Transport: RTP/AVP/UDP;unicast;client_port=3058-3059

   V->C: RTP/AVP;multicast;destination=224.0.1.11;
                    port=21010-21011;mode=record;ttl=127

   M->C: RTSP/1.0 200 OK
         CSeq: 1 91
         Session: 23456789 50887676
         Transport: RTP/AVP/UDP;unicast;client_port=3058-3059;
                    server_port=5002-5003

   C->V: PLAY rtsp://video.example.com/twister/video RTP/AVP;multicast;destination=224.0.1.11;
                    port=21010-21011;mode=record;ttl=127

   C->M: SETUP rtsp://server.example.com/meeting/videotrack RTSP/1.0
         CSeq: 2 92
         Session: 23456789
         Range: smpte=0:10:00-

   V->C: 50887676
         Transport: RTP/AVP;multicast;destination=224.0.1.12;
                    port=61010-61011;mode=record;ttl=127

   M->C: RTSP/1.0 200 OK
         CSeq: 2
         Session: 23456789
         Range: smpte=0:10:00-0:20:00
         RTP-Info: url=rtsp://video.example.com/twister/video;
        seq=12312232;rtptime=78712811

   C->A: PLAY rtsp://audio.example.com/twister/audio.en RTSP/1.0
         CSeq: 2
         Session: 12345678
         Range: smpte=0:10:00-

   A->C: 92
         Transport: RTP/AVP;multicast;destination=224.0.1.12;
                    port=61010-61011;mode=record;ttl=127

   C->M: RECORD rtsp://server.example.com/meeting RTSP/1.0 200 OK
         CSeq: 2 93
         Session: 12345678 50887676
         Range: smpte=0:10:00-0:20:00
         RTP-Info: url=rtsp://audio.example.com/twister/audio.en;
        seq=876655;rtptime=1032181

   C->A: TEARDOWN rtsp://audio.example.com/twister/audio.en RTSP/1.0
         CSeq: 3
         Session: 12345678

   A->C: RTSP/1.0 200 OK
         CSeq: 3

   C->V: TEARDOWN rtsp://video.example.com/twister/video RTSP/1.0
         CSeq: 3
         Session: 23456789

   V->C: clock=19961110T1925-19961110T2015

   M->C: RTSP/1.0 200 OK
         CSeq: 3

   Even though the audio and video track are on two different servers,
   and may start at slightly different times 93

15 RTSP and may drift with respect
   to each other, the client can synchronize the two using standard RTP
   methods, in particular the time scale contained in the RTCP sender
   reports.

14.2 Streaming of a Container file
   For purposes of this example, a container file NATs

15.1 Introduction

   Today there is Network Address Translators (NAT)  [32] everywhere and
   a storage entity protocol must make sure that it can work over them in
   which multiple continuous media types pertaining to the same end-user
   presentation are present. In effect, the container file represents an
   RTSP presentation, some fashion.
   The problem with each of its components being RTSP streams.
   Container files are a widely used means to store such presentations.
   While the components are transported as independent streams, it is
   desirable to maintain a common context for those streams at the
   server end.

     This enables the server to keep a single storage handle open
     easily. It also allows treating all the streams equally in
     case of any prioritization of streams by the server.

   It is also possible that it carries information about network
   addresses and ports inside it self. When the presentation author may wish to prevent
   selective retrieval of the media streams by the client who's
   addresses referred in order RTSP are changed to preserve
   the artistic effect of the combined media presentation. Similarly, in
   such a tightly bound presentation, protocol stops working.

15.2 STUN

   To make STUN work together with RTP/RTCP it is desirable to will be able needed to con-
   trol all have
   the streams via a single control message using an aggregate
   URL.

   The following is an example of using a single RTSP session possibility to control
   multiple streams. It also illustrates signal the use RTCP ports independent of aggregate URLs.

   Client C requests the RTP port
   for a presentation from media server M. stream. To accommodate this two new Transport header parameters
   are defined, server_rtcp_port and client_rtcp_port.

15.3 Application Level Gateways

15.4 TCP Tunneling

16 Syntax

   The movie RTSP syntax is
   stored described in a container file. The client has obtained an RTSP URL to augmented Backus-Naur form (BNF)
   as defined in RFC 2234 [14]. Also the container file.

   C->M: DESCRIBE rtsp://foo/twister RTSP/1.0
         CSeq: 1

   M->C: RTSP/1.0 200 OK
         CSeq: 1
         Content-Type: application/sdp
         Content-Length: 164

         v=0
         o=- 2890844256 2890842807 IN IP4 172.16.2.93
         s=RTSP Session
         i=An Example "#" rule from RFC 2616 [26] is
   also defined and used in this syntax description.

16.1 Base Syntax

   OCTET           =  <any 8-bit sequence of RTSP Session Usage
         a=control:rtsp://foo/twister
         t=0 0
         m=audio 0 RTP/AVP data>
   CHAR            =  <any US-ASCII character (octets 0
         a=control:rtsp://foo/twister/audio
         m=video - 127)>
   UPALPHA         =  <any US-ASCII uppercase letter "A".."Z">
   LOALPHA         =  <any US-ASCII lowercase letter "a".."z">
   ALPHA           =  UPALPHA / LOALPHA
   DIGIT           =  <any US-ASCII digit "0".."9">
   CTL             =  <any US-ASCII control character
                      (octets 0 RTP/AVP 26
         a=control:rtsp://foo/twister/video
   C->M: SETUP rtsp://foo/twister/audio RTSP/1.0
         CSeq: 2
         Transport: RTP/AVP;unicast;client_port=8000-8001

   M->C: RTSP/1.0 200 OK
         CSeq: 2
         Transport: RTP/AVP;unicast;client_port=8000-8001;
                    server_port=9000-9001
         Session: 12345678

   C->M: SETUP rtsp://foo/twister/video RTSP/1.0
         CSeq: 3
         Transport: RTP/AVP;unicast;client_port=8002-8003
         Session: 12345678

   M->C: RTSP/1.0 200 OK
         CSeq: 3
         Transport: RTP/AVP;unicast;client_port=8002-8003;
                    server_port=9004-9005
         Session: 12345678

   C->M: PLAY rtsp://foo/twister RTSP/1.0
         CSeq: 4
         Range: npt=0-
         Session: 12345678

   M->C: - 31) and DEL (127)>
   CR              =  <US-ASCII CR, carriage return (13)>
   LF              =  <US-ASCII LF, linefeed (10)>
   SP              =  <US-ASCII SP, space (32)>
   HT              =  <US-ASCII HT, horizontal-tab (9)>
   <">             =  <US-ASCII double-quote mark (34)>
   BACKSLASH       =  <US-ASCII backslash (92)>
   CRLF            =  CR LF
   LWS             =  [CRLF] 1*( SP / HT )
   TEXT            =  <any OCTET except CTLs>
   tspecials       =  "(" / ")" / "<" / ">" / "@"
                  /   "," / ";" / ":" / BACKSLASH / <">
                  /   "/" / "[" / "]" / "?" / "="
                  /   "{" / "}" / SP / HT
   token           =  1*<any CHAR except CTLs or tspecials>
   quoted-string   =  ( <"> *(qdtext) <"> )
   qdtext          =  <any TEXT except <">>
   quoted-pair     =  BACKSLASH CHAR
   message-header  =  field-name ":" [ field-value ] CRLF
   field-name      =  token
   field-value     =  *( field-content / LWS )
   field-content   =  <the OCTETs making up the field-value and
                     consisting
                     of either *TEXT or combinations of token, tspecials,
                     and quoted-string>
   safe            =  "$" / "-" / "_" / "." / "+"
   extra           =  "!" / "*" / "'" / "(" / ")" / ","
   hex             =  DIGIT / "A" / "B" / "C" / "D" / "E" / "F" /
                      "a" / "b" / "c" / "d" / "e" / "f"
   escape          =  "%" hex hex
   reserved        =  ";" / "/" / "?" / ":" / "@" / "&" / "="
   unreserved      =  alpha / digit / safe / extra
   xchar           =  unreserved / reserved / escape

16.2 RTSP Protocol Definition

   generRTSP-message=  st=rtRequest / Response ; RTSP/1.0 200 messages
                       *(message-header CRLF)
                       CRLF
                       [ message-body ]
   start-line       =  Request-Line / Status-Line
        Request  g=nerRequest-Line ; Sec;iSection 6.1
             /   request-header    ; Section 6.2
             /   entity-header )   ; Section 8.1
                 CRLF
                 [ message-body ]  ; Section 4.3
   Response  =   Status-Line       ; Section 7.1
             *(  general-header    ; Section 5
             /   response-header   ; Section 7.1.2
             /   entity-header )   ; Section 8.1
                 CRLF
                 [ message-body ]  ; Section 4.3

   Request-Line  =  Method SP Request-URI SP RTSP-Version CRLF
   Status-Line   =  RTSP-Version SP Status-Code SP Reason-Phrase CRLF

   Method  =  "DESCRIBE"        ; Section 10.2
           /  "ANNOUNCE"        ; Section 10.3
           /  "GET_PARAMETER"   ; Section 10.8
           /  "OPTIONS"         ; Section 10.1
           /  "PAUSE"           ; Section 10.6
           /  "PLAY"            ; Section 10.5
           /  "PING"            ; Section 10.12
           /  "RECORD"          ; Section 10.11
           /  "REDIRECT"        ; Section 10.10
           /  "SETUP"           ; Section 10.4
           /  "SET_PARAMETER"   ; Section 10.9
           /  "TEARDOWN"        ; Section 10.7
           /  extension-method

   extension-method  =  token
   Request-URI       =  "*" / absolute_URI
   RTSP-Version      =  "RTSP" "/" 1*DIGIT "." 1*DIGIT

     Status-Code  =  "100"           ; Continue
                  /  "200"           ; OK
         CSeq: 4
         Session: 12345678
         RTP-Info: url=rtsp://foo/twister/video;
        seq=9810092;rtptime=3450012

   C->M: PAUSE rtsp://foo/twister/video RTSP/1.0
         CSeq: 5
         Session: 12345678

   M->C: RTSP/1.0 460
                  /  "201"           ; Created
                  /  "250"           ; Low on Storage Space
                  /  "300"           ; Multiple Choices
                  /  "301"           ; Moved Permanently
                  /  "302"           ; Moved Temporarily
                  /  "303"           ; See Other
                  /  "304"           ; Not Modified
                  /  "305"           ; Use Proxy
                  /  "400"           ; Bad Request
                  /  "401"           ; Unauthorized
                  /  "402"           ; Payment Required
                  /  "403"           ; Forbidden
                  /  "404"           ; Not Found
                  /  "405"           ; Method Not Allowed
                  /  "406"           ; Not Acceptable
                  /  "407"           ; Proxy Authentication Required
                  /  "408"           ; Request Time-out
                  /  "410"           ; Gone
                  /  "411"           ; Length Required
                  /  "412"           ; Precondition Failed
                  /  "413"           ; Request Entity Too Large
                  /  "414"           ; Request-URI Too Large
                  /  "415"           ; Unsupported Media Type
                  /  "451"           ; Parameter Not Understood
                  /  "452"           ; reserved
                  /  "453"           ; Not Enough Bandwidth
                  /  "454"           ; Session Not Found
                  /  "455"           ; Method Not Valid in This State
                  /  "456"           ; Header Field Not Valid for Resource
                  /  "457"           ; Invalid Range
                  /  "458"           ; Parameter Is Read-Only
                  /  "459"           ; Aggregate operation not allowed
                  /  "460"           ; Only aggregate operation allowed
         CSeq: 5

   C->M: PAUSE rtsp://foo/twister RTSP/1.0
         CSeq: 6
         Session: 12345678

   M->C: RTSP/1.0 200 OK
         CSeq: 6
         Session: 12345678

   C->M: SETUP rtsp://foo/twister RTSP/1.0
         CSeq: 7
         Transport: RTP/AVP;unicast;client_port=10000

   M->C: RTSP/1.0 459 Aggregate operation
                  /  "461"           ; Unsupported transport
                  /  "462"           ; Destination unreachable
                  /  "500"           ; Internal Server Error
                  /  "501"           ; Not Implemented
                  /  "502"           ; Bad Gateway
                  /  "503"           ; Service Unavailable
                  /  "504"           ; Gateway Time-out
                  /  "505"           ; RTSP Version not allowed
         CSeq: 7

   In the first instance of failure, the client tries supported
                  /  "551"           ; Option not supported
                  /  extension-code

     extension-code  =  3DIGIT
     Reason-Phrase   =  *<TEXT, excluding CR, LF>
   general-header  =  Cache-Control      ; Section 12.9
                   /  Connection         ; Section 12.10
                   /  CSeq               ; Section 12.17
                   /  Date               ; Section 12.18
                   /  Timestamp          ; Section 12.39
                   /  Via                ; Section 12.44
   request-header  =  Accept             ; Section 12.1
                   /  Accept-Encoding    ; Section 12.2
                   /  Accept-Language    ; Section 12.3
                   /  Authorization      ; Section 12.6
                   /  Bandwidth          ; Section 12.7
                   /  Blocksize          ; Section 12.8
                   /  From               ; Section 12.20
                   /  If-Modified-Since  ; Section 12.23
                   /  Proxy-Require      ; Section 12.27
                   /  Range              ; Section 12.29
                   /  Referer            ; Section 12.30
                   /  Require            ; Section 12.32
                   /  Scale              ; Section 12.34
                   /  Session            ; Section 12.37
                   /  Speed              ; Section 12.35
                   /  Supported          ; Section 12.38
                   /  Transport          ; Section 12.40
                   /  User-Agent         ; Section 12.42

   response-header  =  Accept-Ranges       ; Section 12.4
                    /  Location            ; Section 12.25
                    /  Proxy-Authenticate  ; Section 12.26
                    /  Public              ; Section 12.28
                    /  Range               ; Section 12.29
                    /  Retry-After         ; Section 12.31
                    /  RTP-Info            ; Section 12.33
                    /  Scale               ; Section 12.34
                    /  Session             ; Section 12.37
                    /  Server              ; Section 12.36
                    /  Speed               ; Section 12.35
                    /  Transport           ; Section 12.40
                    /  Unsupported         ; Section 12.41
                    /  Vary                ; Section 12.43
                    /  WWW-Authenticate    ; Section 12.45

   rtsp_URL          =  ( "rtsp:" / "rtspu:" / "rtsps" )
                        "//" host [ ":" port ] [ abs_path ]
   host              =  As defined by RFC 2732 [30]
   abs_path          =  As defined by RFC 2396 [22]
   port              =  *DIGIT
   smpte-range       =  smpte-type "=" smpte-range-spec
   smpte-range-spec  =  ( smpte-time "-" [ smpte-time ] ) / ( "-" smpte-time )
   smpte-type        =  "smpte" / "smpte-30-drop" / "smpte-25"
                        ; other timecodes may be added
   smpte-time        =  1*2DIGIT ":" 1*2DIGIT ":" 1*2DIGIT
                        [ ":" 1*2DIGIT [ "." 1*2DIGIT ] ]

   npt-range       =  ["npt" "="] npt-range-spec
                      ; implementations SHOULD use npt= prefix, but SHOULD
                      ; be prepared to pause one
   stream (in this case video) interoperate with RFC 2326
                      ; implementations which don't use it
   npt-range-spec  =  ( npt-time "-" [ npt-time ] ) / ( "-" npt-time )
   npt-time        =  "now" / npt-sec / npt-hhmmss
   npt-sec         =  1*DIGIT [ "." *DIGIT ]
   npt-hhmmss      =  npt-hh ":" npt-mm ":" npt-ss [ "." *DIGIT ]
   npt-hh          =  1*DIGIT ; any positive number
   npt-mm          =  1*2DIGIT ; 0-59
   npt-ss          =  1*2DIGIT ; 0-59
   utc-range       =  "clock" "=" utc-range-spec
   utc-range-spec  =  ( utc-time "-" [ utc-time ] ) / ( "-" utc-time )
   utc-time        =  utc-date "T" utc-time "Z"
   utc-date        =  8DIGIT ; < YYYYMMDD >
   utc-time        =  6DIGIT [ "." fraction ]; < HHMMSS.fraction >
   fraction        =  1*DIGIT

   option-tag  =  token

17 Security Considerations

   Because of the presentation. This is disallowed
   for that presentation by the server. In similarity in syntax and usage between RTSP servers
   and HTTP servers, the second instance, security considerations outlined in [H15]
   apply.  Specifically, please note the
   aggregate URL may not be used for SETUP following:

     Authentication Mechanisms: RTSP and one control message is
   required per stream to set up transport parameters.

     This keeps HTTP share common authentica-
          tion schemes, and thus should follow the syntax same prescriptions
          with regards to authentication . See chapter 15.1 of the Transport header simple [2] for
          client authentication issues, and
     allows easy parsing chapter 15.2 of transport information by firewalls.

14.3 Single Stream Container Files

   Some [2] for
          issues regarding support for multiple authentication mecha-
          nisms. Also see [H15.6].

     Abuse of Server Log Information: RTSP and HTTP servers may treat all files as though they are "container
   files", yet other servers may not support such a concept. Because will presum-
          ably have similar logging mechanisms, and thus should be
          equally guarded in protecting the contents of
   this, clients SHOULD use those logs, thus
          protecting the rules set forth in privacy of the session descrip-
   tion users of the servers. See
          [H15.1.1] for request URLs, rather than assuming HTTP server recommendations regarding server
          logs.

     Transfer of Sensitive Information: There is no reason to believe
          that a consistent URL information transferred via RTSP may
   always be used throughout. Here's an example any less sensi-
          tive than that normally transmitted via HTTP. Therefore, all
          of how a multi-stream
   server might expect a single-stream file the precautions regarding the protection of data privacy
          and user privacy apply to be served:

       C->S  DESCRIBE rtsp://foo.com/test.wav RTSP/1.0
             Accept: application/x-rtsp-mh, application/sdp
             CSeq: 1

       S->C  RTSP/1.0 200 OK
             CSeq: 1
             Content-base: rtsp://foo.com/test.wav/
             Content-type: application/sdp
             Content-length: 48

             v=0
             o=- 872653257 872653257 IN IP4 172.16.2.187
             s=mu-law wave implementors of RTSP clients,
          servers, and proxies. See [H15.1.2] for further details.

     Attacks Based On File and Path Names: Though RTSP URLs are opaque
          handles that do not necessarily have file
             i=audio test
             t=0 0
             m=audio 0 RTP/AVP 0
             a=control:streamid=0

       C->S  SETUP rtsp://foo.com/test.wav/streamid=0 RTSP/1.0
             Transport: RTP/AVP/UDP;unicast;
                        client_port=6970-6971;mode="PLAY"
             CSeq: 2

       S->C  RTSP/1.0 200 OK
             Transport: RTP/AVP/UDP;unicast;client_port=6970-6971;
                        server_port=6970-6971;mode="PLAY"
             CSeq: 2
             Session: 2034820394

       C->S  PLAY rtsp://foo.com/test.wav RTSP/1.0
             CSeq: 3
             Session: 2034820394

       S->C  RTSP/1.0 200 OK
             CSeq: 3
             Session: 2034820394
             RTP-Info: url=rtsp://foo.com/test.wav/streamid=0;
               seq=981888;rtptime=3781123

   Note system semantics, it
          is anticipated that many implementations will translate por-
          tions of the different URL request URLs directly to file system calls. In
          such cases, file systems SHOULD follow the precautions out-
          lined in [H15.5], such as checking for ".." in path compo-
          nents.

     Personal Information: RTSP clients are often privy to the SETUP command, same
          information that HTTP clients are (user name, location, etc.)
          and then the switch back thus should be equally. See [H15.1] for further recommen-
          dations.

     Privacy Issues Connected to Accept Headers: Since may of the aggregate URL same
          "Accept" headers exist in RTSP as in HTTP, the PLAY command. This makes complete sense
   when there are multiple streams same caveats
          outlined in [H15.1.4] with aggregate control, but is regards to their use should be fol-
          lowed.

     DNS Spoofing: Presumably, given the longer connection times typi-
          cally associated to RTSP sessions relative to HTTP sessions,
          RTSP client DNS optimizations should be less
   than intuitive prevalent.
          Nonetheless, the recommendations provided in [H15.3] are still
          relevant to any implementation which attempts to rely on a
          DNS-to-IP mapping to hold beyond a single use of the special case where mapping.

     Location Headers and Spoofing: If a single server supports multiple
          organizations that do not trust one another, then it must
          check the number values of streams is
   one.

   In this special case, it is recommended Location and Content-Location header
          fields in responses that servers be forgiving are generated under control of
   implementations said
          organizations to make sure that send:

       C->S  PLAY rtsp://foo.com/test.wav/streamid=0 RTSP/1.0
             CSeq: 3 they do not attempt to invali-
          date resources over which they have no authority. ([H15.4])

   In addition to the worst case, servers should send back:

       S->C  RTSP/1.0 460 Only aggregate operation allowed
             CSeq: 3

   One would also hope that server implementations are recommendations in the current HTTP specification
   (RFC 2616 [26], as of this writing) and also forgiving of the following:

       C->S  SETUP rtsp://foo.com/test.wav RTSP/1.0
             Transport: rtp/avp/udp;client_port=6970-6971;mode="PLAY"
             CSeq: 2

   Since there is only a single stream in this file, it's not ambiguous
   what this means.

14.4 Live Media Presentation Using Multicast previous RFC2068
   [2], future HTTP specifications may provide additional guidance on
   security issues.

   The media server M chooses the multicast address and port. Here, we
   assume that following are added considerations for RTSP implementations.

     Concentrated denial-of-service attack: The protocol offers the web server only contains
          opportunity for a pointer remote-controlled denial-of-service attack.

          The attacker may initiate traffic flows to one or more IP
          addresses by specifying them as the full
   description, while destination in SETUP
          requests. While the media server M maintains attacker's IP address may be known in this
          case, this is not always useful in prevention of more attacks
          or ascertaining the full description.

   C->W: GET /concert.sdp HTTP/1.1
         Host: www.example.com

   W->C: HTTP/1.1 200 OK
         Content-Type: application/x-rtsl

         <session>
           <track src="rtsp://live.example.com/concert/audio">
         </session>

   C->M: DESCRIBE rtsp://live.example.com/concert/audio RTSP/1.0
         CSeq: 1

   M->C: RTSP/1.0 200 OK
         CSeq: 1
         Content-Type: application/sdp
         Content-Length: 44

         v=0
         o=- 2890844526 2890842807 IN IP4 192.16.24.202
         s=RTSP Session
         m=audio 3456 RTP/AVP 0
         c=IN IP4 224.2.0.1/16
         a=control:rtsp://live.example.com/concert/audio

   C->M: SETUP rtsp://live.example.com/concert/audio RTSP/1.0
         CSeq: 2
         Transport: RTP/AVP;multicast

   M->C: RTSP/1.0 200 OK
         CSeq: 2
         Transport: RTP/AVP;multicast;destination=224.2.0.1;
                    port=3456-3457;ttl=16
         Session: 0456804596

   C->M: PLAY rtsp://live.example.com/concert/audio RTSP/1.0
         CSeq: 3
         Session: 0456804596

   M->C: RTSP/1.0 200 OK
         CSeq: 3
         Session: 0456804596

14.5 Recording

   The conference participant client C asks attackers identity. Thus, an RTSP server
          SHOULD only allow client-specified destinations for RTSP-ini-
          tiated traffic flows if the media server M to record has verified the audio and video portions client's
          identity, either against a database of known users using RTSP
          authentication mechanisms (preferably digest authentication or
          stronger), or other secure means.                              |

     Session hijacking: Since there is no or little relation between a meeting. The   |
          transport layer connection and an RTSP session, it is possible |
          for a malicious client uses the
   ANNOUNCE method to provide meta-information about the recorded ses-
   sion issue requests with random session   |
          identifiers which would affect unsuspecting clients. The       |
          server SHOULD use a large, random and non-sequential session   |
          identifier to minimize the server.

   C->M: ANNOUNCE rtsp://server.example.com/meeting RTSP/1.0
         CSeq: 90
         Content-Type: application/sdp
         Content-Length: 121

         v=0
         o=camera1 3080117314 3080118787 IN IP4 195.27.192.36
         s=IETF Meeting, Munich - 1
         i=The thirty-ninth IETF meeting will possibility of this kind of attack.

     Authentication: Servers SHOULD implement both basic and digest [6]
          authentication. In environments requiring tighter security for
          the control messages, transport layer mechanisms such as TLS
          (RFC 2246 [27]) SHOULD be held in Munich, Germany
         u=http://www.ietf.org/meetings/Munich.html
         e=IETF Channel 1 <ietf39-mbone@uni-koeln.de>
         p=IETF Channel 1 +49-172-2312 451
         c=IN IP4 224.0.1.11/127
         t=3080271600 3080703600
         a=tool:sdr v2.4a6
         a=type:test
         m=audio 21010 RTP/AVP 5
         c=IN IP4 224.0.1.11/127
         a=ptime:40
         m=video 61010 RTP/AVP 31
         c=IN IP4 224.0.1.12/127

   M->C: RTSP/1.0 200 OK
         CSeq: 90

   C->M: SETUP rtsp://server.example.com/meeting/audiotrack RTSP/1.0
         CSeq: 91
         Transport: RTP/AVP;multicast;destination=224.0.1.11;
                    port=21010-21011;mode=record;ttl=127

   M->C: RTSP/1.0 200 OK
         CSeq: 91
         Session: 50887676
         Transport: RTP/AVP;multicast;destination=224.0.1.11;
                    port=21010-21011;mode=record;ttl=127

   C->M: SETUP rtsp://server.example.com/meeting/videotrack RTSP/1.0
         CSeq: 92
         Session: 50887676
         Transport: RTP/AVP;multicast;destination=224.0.1.12;
                    port=61010-61011;mode=record;ttl=127

   M->C: RTSP/1.0 200 OK
         CSeq: 92
         Transport: RTP/AVP;multicast;destination=224.0.1.12;
                    port=61010-61011;mode=record;ttl=127

   C->M: RECORD rtsp://server.example.com/meeting RTSP/1.0
         CSeq: 93
         Session: 50887676
         Range: clock=19961110T1925-19961110T2015

   M->C: RTSP/1.0 200 OK
         CSeq: 93

15 Syntax

   The used.

     Stream issues: RTSP syntax is described only provides for stream control. Stream deliv-
          ery issues are not covered in an augmented Backus-Naur form (BNF)
   as used this section, nor in RFC 2068 [2].

15.1 Base Syntax

   OCTET           =  <any 8-bit sequence the rest of data>
   CHAR            =  <any US-ASCII character (octets 0 - 127)>
   UPALPHA         =  <any US-ASCII uppercase letter "A".."Z">
   LOALPHA         =  <any US-ASCII lowercase letter "a".."z">
   ALPHA           =  UPALPHA | LOALPHA
   DIGIT           =  <any US-ASCII digit "0".."9">
   CTL             =  <any US-ASCII control character
                      (octets 0 - 31) and DEL (127)>
   CR              =  <US-ASCII CR, carriage return (13)>
   LF              =  <US-ASCII LF, linefeed (10)>
   SP              =  <US-ASCII SP, space (32)>
   HT              =  <US-ASCII HT, horizontal-tab (9)>
   <">             =  <US-ASCII double-quote mark (34)>
   BACKSLASH       =  <US-ASCII backslash (92)>
   CRLF            =  CR LF
   LWS             =  [CRLF] 1*( SP | HT )
   TEXT            =  <any OCTET except CTLs>
   tspecials       =  "(" | ")" | "<" | ">" | "@"
                  |   "," | ";" | ":" | BACKSLASH | <">
                  |   "/" | "[" | "]" | "?" | "="
                  |   "{" | "}" | SP | HT
   token           =  1*<any CHAR except CTLs or tspecials>
   quoted-string   =  ( <"> *(qdtext) <"> )
   qdtext          =  <any TEXT except <">>
   quoted-pair     =  BACKSLASH CHAR
   message-header  =  field-name ":" [ field-value ] CRLF
   field-name      =  token
   field-value     =  *( field-content | LWS )
   field-content   =  <the OCTETs making
          this draft. RTSP implementations will most likely rely on
          other protocols such as RTP, IP multicast, RSVP and IGMP, and
          should address security considerations brought up the field-value in those and
                     consisting
          other applicable specifications.

     Persistently suspicious behavior: RTSP servers SHOULD return error
          code 403 (Forbidden) upon receiving a single instance of either *TEXT or combinations
          behavior which is deemed a security risk. RTSP servers SHOULD
          also be aware of token, tspecials, attempts to probe the server for weaknesses
          and quoted-string>
   safe            =  "$" | "-" | "_" | "." | "+"
   extra           =  "!" | "*" | "'" | "(" | ")" | ","
   hex             =  DIGIT entry points and MAY arbitrarily disconnect and ignore
          further requests clients which are deemed to be in violation
          of local security policy.

18 IANA Considerations
   This section set up a number of registers for RTSP that should be     | "A"
   maintained by IANA. For each registry there is a description on what  | "B"
   it shall contain, what specification is needed when adding a entry    | "C"
   with IANA, and finally the entries that this document needs to regis- | "D"
   ter. See also the section 1.6 "Extending RTSP".                       | "E"

   The sections describing how to register an item uses some of the      | "F"
   requirements level described in RFC 2434 [29], namely " First Come,   |
                      "a"
   First Served", "Specification Required", and "Standards Action".      | "b"

   A registration request to IANA MUST contain the following informa-    | "c"
   tion:                                                                 | "d"

     + A name of the item to register according to the rules specified   | "e"
       by the intended registry.                                         | "f"
   escape          =  "%" hex hex
   reserved        =  ";"

     + Indication of who has change control over the option (for exam-   | "/"
       ple, IETF, ISO, ITU-T, other international standardization bod-   | "?"
       ies, a consortium or a particular company or group of companies); | ":"

     + A reference to a further description, if available, for example   | "@"
       (in order of preference) an RFC, a published standard, a pub-     | "&"
       lished paper, a patent filing, a technical report, documented     | "="
   unreserved      =  alpha
       source code or a computer manual;                                 | digit

     + For proprietary options, contact information (postal and email    | safe
       address);                                                         | extra
   xchar           =  unreserved

18.1 Option-tags                                                         | reserved

18.1.1 Description                                                       | escape

16 Security Considerations

   Because of the similarity in syntax

   When a client and usage between RTSP servers server try to determine what part and HTTP servers, the security considerations outlined in [H15]
   apply.  Specifically, please note functionality |
   of the following:

     Authentication Mechanisms: RTSP specification and HTTP share common authentica-
          tion schemes, and thus should follow the same prescriptions
          with regards to authentication. See chapter 15.1 of [2] for
          client authentication issues, and chapter 15.2 of [2] for
          issues regarding support any future extensions that its counter  |
   part implements there is need for multiple authentication mecha-
          nisms.

     Abuse a namespace.  This registry con-    |
   tains named entries representing certain functionality.               |

   The usage of Server Log Information: RTSP and HTTP servers will presum-
          ably have similar logging mechanisms, and thus should be
          equally guarded option-tags is explained in protecting the contents of those logs, thus
          protecting the privacy of the users of the servers. See
          [H15.1.1] for HTTP server recommendations regarding server
          logs.

     Transfer section 3.7 and 10.1.        |

18.1.2 Registering New Option Tags with IANA                             |

   The registering of Sensitive Information: There option tags is no reason to believe
          that information transferred via RTSP done on a first come, first served  |
   basis.                                                                |

   The name of the option MUST follow these rules: The name may be of    |
   any less sensi-
          tive length, but SHOULD be no more than that normally transmitted via HTTP. Therefore, all
          of the precautions regarding the protection of data privacy
          and user privacy apply to implementors of RTSP clients,
          servers, and proxies. See [H15.1.2] for further details.

     Attacks Based On File and Path Names: Though RTSP URLs are opaque
          handles that do twenty characters long.  The   |
   name MUST not necessarily contain any spaces, or control characters. Any propri-  |
   etary option SHALL have file system semantics, it
          is anticipated that many implementations will translate por-
          tions as the first part of the request URLs directly to file system calls. In
          such cases, file systems SHOULD follow name a vendor tag,   |
   which identifies the precautions out-
          lined in [H15.5], such as checking for ".." in path compo-
          nents.

     Personal Information: RTSP clients organization.                                    |

18.1.3 Registered entries                                                |

   The following options tags are often privy in this specification defined and      |
   hereby registered. The change control belongs to the same
          information that HTTP clients are (user name, location, etc.) Authors and thus should be equally. See [H15.1] the  |
   IETF MMUSIC WG.                                                       |

     play.basic: The minimal implementation for further recommen-
          dations.

     Privacy Issues Connected playback operations      |
          according to Accept Headers: Since may section D.                                        |

     play.scale: Support of scale operations for media playback.         |

     play.speed: Support of the same
          "Accept" headers exist in RTSP as in HTTP, the same caveats
          outlined in [H15.1.4] with regards to their use should be fol-
          lowed.

     DNS Spoofing: Presumably, given the longer connection times typi-
          cally associated to RTSP sessions relative to HTTP sessions,
          RTSP client DNS optimizations should be less prevalent.
          Nonetheless, the recommendations provided in [H15.3] are still
          relevant to any speed functionality for playback.        |

     record.basic: The minimal implementation which attempts to rely on a
          DNS-to-IP mapping for record operations      |
          according to hold beyond a single section D.                                        |

     record.setup: The use of the mapping.

     Location Headers and Spoofing: If a single server supports multiple
          organizations that do not trust one another, then it must
          check the values of Location setup and Content-Location header
          fields teardown in responses that are generated under control record state.        |

     record.scale: Support of said
          organizations to make sure that they do not attempt to invali-
          date resources over which they have no authority. ([H15.4])

   In addition to the recommendations scale operations for media recording.      |

     setup.playing: The use of teardown and setup in the current HTTP specification
   (RFC 2616 [26], as play state.         |

     con.non-persistent: Support and use of this writing) non-persistent connections,  |
          see chapter  9.3.                                              |

     con.persistent: Support and also use of persistent connections, see      |
          chapter  9.3.                                                  |

18.2 RTSP Methods                                                        |

18.2.1 Description                                                       |

   What a method is, is described in section 10.  Extending the previous RFC2068
   [2], future HTTP specifications may provide additional guidance on
   security issues. protocol |
   with new methods allow for totally new functionality.                 |

18.2.2 Registering New Methods with IANA                                 |

   A new method MUST be registered through an IETF standard track docu-  |
   ment. The following are added considerations reason is that new methods may radically change the proto-  |
   cols behavior and purpose.                                            |

   A specification for a new RTSP implementations.

     Concentrated denial-of-service attack: The protocol offers method MUST consist of the
          opportunity following   |
   items:                                                                |

     + A method name which follows the BNF rules for methods.            |
     + A clear specification on what action and response a remote-controlled denial-of-service attack.

          The attacker may initiate traffic flows to one or more IP
          addresses by specifying them as request with  |
       the destination in SETUP
          requests. While method will result in. Which directions the attacker's IP address may be known in this
          case, this method is not always useful in prevention of more attacks used,   |
       C->S or ascertaining S->C or both. How the attackers identity. Thus, an RTSP server
          SHOULD only allow client-specified destinations for RTSP-ini-
          tiated traffic flows use of headers, if any, modifies    |
       the server has verified the client's
          identity, either against a database behavior and effect of known users using RTSP
          authentication mechanisms (preferably digest authentication or
          stronger), the method.                            |

     + A list or other secure means.

     Session hijacking: Since there is no relation between a transport
          layer connection and an RTSP session, it is possible for a
          malicious client to issue requests with random session identi-
          fiers table specifying which would affect unsuspecting clients. The server
          SHOULD use a large, random and non-sequential session identi-
          fier to minimize the possibility of this kind of attack.

     Authentication: Servers SHOULD implement both basic and digest [6]
          authentication. In environments requiring tighter security for the control messages, transport layer mechanisms such as TLS
          (RFC 2246 [27]) SHOULD be used.

     Stream issues: RTSP only provides for stream control. Stream deliv-
          ery issues registered headers that   |
       are not covered in this section, nor in allowed to use with the rest of
          this draft. RTSP implementations will most likely rely on
          other protocols such as RTP, IP multicast, RSVP and IGMP, and
          should address security considerations brought up method in those request or/and response.    |

     + Describe how the method relates to network proxies.               |

18.2.3 Registered Entries                                                |

   This specification, RFCXXXX, registers 12 methods: DESCRIBE,          |
   ANNOUNCE, GET_PARAMETER, OPTIONS, PAUSE, PING, PLAY, RECORD, REDI-    |
   RECT, SETUP, SET_PARAMETER, and
          other applicable specifications.

     Persistently suspicious behavior: TEARDOWN.                             |

18.3 RTSP servers SHOULD return error Status Codes                                                   |

18.3.1 Description                                                       |

   A status code 403 (Forbidden) upon receiving a single instance of
          behavior which is deemed a security risk. the three digit numbers used to convey information   |
   in RTSP servers SHOULD
          also response messages, see  7.  The number space is limited and   |
   care should be aware of attempts taken not to probe fill the server space.                           |

18.3.2 Registering New Status Codes with IANA                            |

   A new status code can only be registered by an IETF standards track   |
   document. A specification for weaknesses
          and entry points and MAY arbitrarily disconnect a new status code MUST specify the fol- |
   lowing:                                                               |

     + The requested number.                                             |

     + A description what the status code means and ignore
          further requests clients which are deemed to be in violation the expected behav-  |
       ior of local security policy.

17 IANA Considerations
   This section set up a number the sender and receiver of the code.                       |

18.3.3 Registered Entries                                                |

   RFCXXX, registers for the numbered status code defined in the BNF entry   |
   "Status-Code" except "extension-code" in section 7.1.1.               |

18.4 RTSP that should Headers                                                        |

18.4.1 Description                                                       |

   By specifying new headers a method(s) can be
   maintained enhanced in many differ- |
   ent ways. An unknown header will be ignored by IANA. For each registry there the receiving entity.  |
   If the new header is vital for a description on what
   it shall contain, what specification is needed when adding certain functionality, a entry
   with IANA, and finally option tag  |
   for the entries that this document needs functionality can be created and demanded to regis-
   ter. See also be used by the section 1.5 "Extending RTSP".

   The sections describing how to register an item uses some   |
   counter-part with the inclusion of a Require header carrying the
   requirements level described in RFC 2434 [29], namely " First Come,
   First Served", "Specification Required", and "Standards Action".      |
   option tag.                                                           |

18.4.2 Registering New Headers with IANA                                 |

   A registration request public available specification is required to IANA register a header.    |
   The specification SHOULD be a standards document, preferable an IETF  |
   RFC.                                                                  |

   The specification MUST contain the following informa-
   tion: information:             |

     + A The name of the item to register according to the rules specified
       by the intended registry. header.                                           |

     + Indication A BNF specification of who has change control over the option (for exam-
       ple, IETF, ISO, ITU-T, other international standardization bod-
       ies, a consortium header syntax.                         |

     + A list or a particular company table specifying when the header may be used, encom-    |
       passing all methods, their request or group of companies); response, the direction     |
       (C->S or S->C).                                                   |

     + How the header shall be handled by proxies.                       |

     + A reference to a further description, if available, for example
       (in order description of preference) an RFC, a published paper, a patent fil-
       ing, a technical report, documented source code or a computer
       manual;

     + For proprietary options, contact information (postal and email
       address);

17.1 Option-tags

17.1.1 Description

   When a client and server try to determine what part and functionality the purpose of the RTSP specification and any future extensions that its counter
   part implements there is need for a namespace.  This registry con-
   tains named header.                       |

18.4.3 Registered entries representing certain functionality.

   The usage of option-tags is explained                                                |

   All headers specified in section 3.7 12 in RFCXXXX are to be registered.  |

18.5 Parameters                                                          |

18.5.1 Description                                                       |

   A Parameter allow the counterpart to set something with the owner of  |
   the parameter. Both the client and 10.1.

17.1.2 the server can have parameters.    |

18.5.2 Registering New Option Tags Parameters with IANA

   The registering of option tags                              |

   Any Parameter is done registered on a first come, first served basis.  The |
   following rules apply for parameters:                                 |

     + The parameter name of the option MUST follow these rules: is a BNF token. The name may be of
   any length, but SHOULD not be no more    |
       than twenty 20 characters long.  The
   name MUST not contain any spaces, control characters or periods. Any proprietary option SHOULD have as the first part of the name a vendor
   tag, which identifies the company/person.

17.1.3 Registered entries

   The following options tags are in this specification defined and
   hereby registered. The change control belongs to the Authors and the
   IETF MMUSIC WG.

     play-basic: The minimal implementation for playback operations
          according to section D.

     record-basic: The minimal implementation for record operations
          according to section D.

     play-setup: The use of teardown and setup in play state.

     record-setup: The use of setup and teardown in record state.

17.2 RTSP Methods

17.2.1 Description

   What parameter should start   |
       the name with a method is, is described vendor tag, as clearly as possible identifying    |
       the company or person.                                            |

     + Any non proprietary parameter MUST in section 10.  Extending the protocol
   with new methods allow for totally new functionality.

17.2.2 Registering New Methods form of BNF specify     |
       what value types that are associated with IANA

   A the parameter.          |

18.5.3 Registered entries                                                |

   For the moment no known parameters are defined in RFC XXXX.           |

18.6 MIME type registration                                              |

   One new method can only MIME type is registered, text/parameters. To be registered through an IETF standards action. defined.      |

18.7 Transport Header registries                                         |

   The reason is that new methods may radically change the protocols
   behavior and purpose.

   A specification for transport header contains a new RTSP method MUST consist number of parameters which have pos-  |
   sibilities for future extensions. Therefore registries for these must |
   be defined.                                                           |

18.7.1 Transport Protocols                                               |

   A registry for the parameter transport-protocol shall be defined with |
   the following
   items: rules:                                                  |

     + Registering requires public available standards specification.    |

     + A method name which follows contact person or organization with address and email.          |

     + A value definition that are following the BNF rules for methods. token definition.   |

     + A clear specification on what action and response a request with describing text that explains how the method will result in. Which directions registered value are used |
       in RTSP.                                                          |

   This specification register 1 value:                                  |

     + Use of the method RTP  [23] protocol for media transport. The usage is used,
       C->S or S->C or both. How   |
       explained in RFC XXXX, appendix B.                                |

18.7.2 Profile                                                           |

   A registry for the use of headers, if any, modifies parameter profile shall be defined with the behavior fol-   |
   lowing rules:                                                         |

     + Registering requires public available standards specification.    |

     + A contact person or organization with address and effect of email.          |

     + A value definition that are following the method. BNF token definition.   |

     + A list or table specifying which definition of which Transport protocol(s) that this profile is  |
       valid for.                                                        |
     + A describing text that explains how the registered headers that value are allowed to use with the method used |
       in request or/and response. RTSP.                                                          |

     + Describe how the method relates to network proxies.

17.2.3 Registered entries
   This specification, RFCXXXX, registers 12 methods: DESCRIBE,
   ANNOUNCE, GET_PARAMETER, OPTIONS, PAUSE, PING, PLAY, RECORD, REDI-
   RECT, SETUP, SET_PARAMETER, The "RTP profile for audio and TEARDOWN.

17.3 RTSP Headers

17.3.1 Description

   By specifying new headers a method(s) can be enhanced in many differ-
   ent ways. An unknown header will video conferences with minimal     |
       control"  [1] MUST only be ignored by the receiving entity.
   If used when the new header transport headers trans- |
       port-protocol is vital for a certain functionality, a option tag "RTP".                                           |

18.7.3 Lower Transport                                                   |

   A registry for the functionality can be created and demanded to parameter lower-transport shall be used by the
   counter-part defined with    |
   the inclusion of a Require header carrying the
   option tag.

   Unregistered headers SHALL have a name starting with "X-" to signal
   that it is a experimental header.

17.3.2 following rules:                                                  |

     + Registering New Headers requires public available standards specification.    |

     + A contact person or organization with IANA address and email.          |

     + A specification is required to register a header.

   The specification MUST contain the value definition that are following information: the BNF token definition.   |

     + The header name following A describing text that explains how the BNF definition. registered value are used |
       in RTSP.                                                          |

     + A BNF specification Indicates the use of how information (if any) is carried in the
       header. "User datagram protocol"  [7] for media  |
       transport.                                                        |

     + Indicates the use Transmission control protocol  [9] for media    |
       transport.                                                        |

18.7.4 Transport modes                                                   |

   A list or table specifying when registry for the header may transport parameter mode shall be used, encom-
       passing all methods, their request or response, defined with the direction
       (C->S |
   following rules:                                                      |

     + Registering requires a IETF standard tracks document.             |

     + A contact person or S->C). organization with address and email.          |

     + How A value definition that are following the header shall be handled by proxies. BNF token definition.   |

     + A description of the purpose of describing text that explains how the header.

17.3.3 Registered entries

   All headers specified in section 12 registered value are used |
       in RTSP.                                                          |

     + See RFC XXXX are to XXXX.                                                     |

     + See RFC XXXX.                                                     |

18.8 Cache Directive Extensions                                          |
   There exist a number of cache directives which can be registered.

17.4 Parameters

17.4.1 Description

   A Parameter allow sent in the counterpart to set something     |
   Cache-Control header. A registry for this cache directives shall be   |
   defined with the owner of
   the parameter. Both the client and the server can have parameters.

17.4.2 Registering New Parameters with IANA

   Any Parameter is registered on a first come, first served basis.  The following rules apply for parameters: rules:                                     |

     + The parameter name is Registering requires a BNF token. The name SHOULD not be more
       than 20 characters long. Any proprietary parameter should start
       the IETF standard tracks document.             |

     + A registration shall name with a vendor tag, as clearly as possible identify the
       company or contact person.                       |

     + Any non proprietary parameter MUST in Name of the form directive and a definition of BNF specify
       what value types that are associated with the parameter.

17.4.3 Registered entries

   For value, if any.      |

     + A describing text that explains how the moment no known parameters are defined in RFC XXXX. cache directive is used   |
       for RTSP controlled media streams.                                |

A RTSP Protocol State Machine

   The RTSP session state machine describe the behavior of the protocol  |
   from RTSP session initialization through RTSP session termination.    |

   State machine is defined on a per session basis which is uniquely     |
   identified by the RTSP session identifier. The session may contain    |
   zero or more media streams depending on state. If a single media      |
   stream is part of the session it is in non-aggregated control. If two |
   or more is part of the session it is in aggregated control.           |

   This state machine is one possible representation that helps explain  |
   how the protocol works and when different requests are allowed.  We   |
   find it a reasonable representation but does not mandate it, and      |
   other representations can be created.                                 |

A.1 States                                                               |

   The state machine contains five states, described below. For each     |
   state there exist a table which shows which requests and events that  |
   is allowed and if they will result in a state change.                 |

     Init: Initial state no session exist.                               |

     Ready-nm: Ready state without any medias.                           |

     Ready: Session is ready to start playing or recording.              |

     Play: Session is playing, i.e. sending media stream data in the     |
          direction S->C.                                                |

     Record: Session is recording, i.e. sending media stream data in the |
          direction C->S.                                                |

A.2 State variables                                                      |

   This representation of the state machine needs more than its state to |
   work. A small number of variables are also needed and is explained    |
   below.                                                                |

     NRM: The number of media streams part of this session.              |

     RP: Resume point, the point in the presentation time line at which  |
          a request to continue will resume from. A time format for the  |
          variable is not mandated.                                      |

A.3 Abbreviations                                                        |

   To make the state tables more compact a number of abbreviations are   |
   used, which are explained below.                                      |

     IFI: IF Implemented.                                                |

     md: Media                                                           |

     PP: Pause Point, the point in the presentation time line at which   |
          the presentation was paused.                                   |

     Prs: Presentation, the complete multimedia presentation.

     IFI: IF Implemented.            |

     RedP: Redirect Point, the point in the presentation time line at    |
          which a REDIRECT was specified to occur.                       |

     SES: Session.                                                       |

A.4 State Tables                                                         |

   This section contains a table for each state. The table contains all  |
   the requests and events that this state is allowed to act on.  The    |
   events which is method names are, unless noted, requests with the     |
   given method in the direction client to server (C->S). In some cases  |
   there exist one or more requisite. The response column tells what     |
   type of response actions should be performed. Possible actions that   |
   is requested for an event includes: response codes, e.g. 200, headers |
   that MUST be included in the response, setting of state variables, or |
   setting of other session related parameters. The new state column     |
   tells which state the state machine shall change to.                  |

   The response to valid request meeting the requisites is normally a    |
   2xx (SUCCESS) unless other noted in the response column. The excep-   |
   tions shall be given a response according to the response column. If  |
   the request does not meet the requisite, is erroneous or some other   |
   type of error occur the appropriate response code MUST be sent. If    |
   the response code is a 4xx the session state is unchanged. A response |
   code of 3xx will result in that the session is ended and its state is |
   changed to Init. However there exist restrictions to when a 3xx       |
   response may be used. A 5xx response SHALL not result in any change   |
   of the session state, except if the error is not possible to recover  |
   from. A unrecoverable error SHOULD SHALL result in the ending of the session.   |
   As it in the general case can't be determined if it was a unrecover-  |
   able error or not the client will be required to test. In the case    |
   that the next request after a 5xx is responded with 454 (Session Not  |
   Found) the client SHALL assume that the session has been ended.       |

   The server will timeout the session after the period of time speci-   |
   fied in the SETUP response, if no activity from the client is         |
   detected.  Therefore there exist a timeout event for all states       |
   except Init.                                                          |

   In the case that NRM=1 the presentation URL is equal to the media     |
   URL. For NRM>1 the presentation URL MUST be other than any of the     |
   medias that are part of the session. This applies to all states.      |

   Event         Prerequisite      Response
   -----------------------------------------------------------------
   DESCRIBE      Needs REDIRECT    3xx Redirect
   DESCRIBE                        200, Session description
   OPTIONS       Session ID        200, Reset session timeout timer
   OPTIONS                         200
   SET_PARAMETER Valid parameter   200, change value of parameter
   GET_PARAMETER Valid parameter   200, return value of parameter
   ANNOUNCE      C->S, IFI record. RECORD.
   ANNOUNCE      S->C,             Update SES descr. Session description.

   Table 5: 6: None state-machine changing events

   The methods in Table 5 6 do not have any effect on the state machine or |
   the state variables. However some methods do change other session     |
   related parameters, for example SET_PARAMETER which will set the      |
   parameter(s) specified in its body.                                   |

   The initial state of the state machine, see Table 6 7 can only be left  |
   by processing a correct SETUP request. As seen in the table the two   |
            Action  Requisite       New State  Response
            -------------------------------------------------
            SETUP                     Ready    NRM=1, RP=0.0
            SETUP   Needs Redirect    Init     3xx Redirect

   Table 7: State: Init

   state variables are also set by a correct request. This table also    |
   shows that a correct SETUP can in some cases be redirected to another |
   URL and/or server by a 3xx response.                                  |

       Action         Requisite       New State  Response
            -------------------------------------------------
            SETUP                     Ready    NRM=1, RP=0.0
            SETUP   Needs Redirect    Init     3xx Redirect

   Table 6: State: Init

     Action         Requisite       New State  Response
     --------------------------------------------------------------
       ----------------------------------------------------------
       SETUP                            Ready    NRM=1,RP=0.0
       SETUP          Needs Redirect    Init     3xx
       TEARDOWN       URL=*             Init     No session hdr.
       Timeout                          Init
       S->C:REDIRECT  Range hdr         Play       Ready-nm   Set RedP
       S->C:REDIRECT  no range hdr      Init     Stop Media Playout
       RedP reached                     Init

   Table 7: 8: State: Ready-nm

   The optional Ready-nm state has no media streams and therefore can't  |
   play or record. This state exist so that all session related parameters parame-  |
   ters and resources can be kept while changing media stream(s). As     |
   seen in Table 7 8 the operations are limited to setting up a new media  |
   or tear-
   ing tearing down the session. The established session can also be      |
   redirected with the REDIRECT method.                                  |

   In the Ready state, see Table 8, 9, some of the actions are depending on |
   the number of media streams (NRM) in the session, i.e. aggregated or non-
   aggregated  |
   non-aggregated control. A setup request in the ready state can either |
   add one more media stream to the session or if the media stream (same |
   URL) already is part of the session change the transport parameters.  |
   TEARDOWN is depending on both the request URI and the number of media |
   stream within the session. If the request URI is either * or the pre- |
   sentations URI the whole session is torn down. If a media URL is used |
   in the TEARDOWN request and more than one media exist in the session, |
   the session will remain and a session header MUST be returned in the  |
   response. The number of media streams remain-
   ing after tearing down If only a single media stream determines the new state.

   The Play state table, see Table 9, is remains in the largest. The table contains
   an number of request that has presentation URL as session when   |
   performing a prerequisite on
   the request URL, this TEARDOWN with a media URL , it is due optional to keep the exclusion of non-aggregated
   stream control in sessions with more than one media stream.   |
  Action         Requisite          New State  Response
  ---------------------------------------------------------------------
  SETUP          New URL              Ready    NRM+=1
  SETUP          Setten up URL        Ready    Change transport param.
  TEARDOWN       URL=*                Init     No session hdr
  TEARDOWN       Prs URL,NRM>1        Init     No session hdr
  TEARDOWN       md URL,NRM=1 URL,NRM=1IFI    Ready-nm   Session hdr, NRM=0
  TEARDOWN       md URL,NRM=1         Init     No Session hdr, NRM=0
  TEARDOWN       md URL,NRM>1         Ready    Session hdr, NRM-=1
  PLAY           Prs URL, No range    Play     Play from RP
  PLAY           Prs URL, Range       Play     according to range
  RECORD         Prs URL             Record
  S->C:REDIRECT  Range hdr            Ready    Set RedP
  S->C:REDIRECT  no range hdr         Init
  Timeout                             Init
  RedP reached                        Init

   Table 8: 9: State: Ready

Action         Requisite          New State  Response
------------------------------------------------------------------------
PAUSE          PrsURL,No range      Ready    Set RP to present point
PAUSE          PrsURL,Range>now     Play     Set RP & PP to given point
PAUSE          PrsURL,Range<=now    Ready    Set RP to present pos.
PP reached                          Ready    RP = PP
End

   session. If the session still exist after the request a Session MUST  |
   be returned in the response. The number of media   All media            Play     No action, RP = Invalid
End of streams remaining    |
   after tearing down a media   >=1 Media plays      Play     No action
End of range stream determines the new state.           |

   The Play     Set RP = End state table, see Table 10, is the largest. The table con-    |
   tains an number of range
SETUP          New URL,IFI          Play     NRM+=1, 200, RTP-Info
SETUP          New URL              Play     501
SETUP          Setuped URL          Play     Change transport param.
TEARDOWN       URL=*                Init     No session hdr
TEARDOWN       Prs URL,NRM>1        Init     No session hdr
TEARDOWN       md URL,NRM=1,IFI   Ready-nm   Session hdr
TEARDOWN       md URL,NRM>1,IFI     Play     Session hdr
TEARDOWN       md request that has presentation URL               Play     501
S->C:REDIRECT  Range hdr            Play     Set RedP
S->C:REDIRECT  no range hdr         Init     Stop Media Playout
RedP reached                        Init     Stop Media playout
Timeout                             Init

   Table 9: State: Play as a prerequi-   |
   site on the request URL, this is due to the exclusion of non-aggre-   |
   gated stream control in sessions with more than one media stream.     |

   To avoid inconsistencies between the client and server, automatic     |
   state transitions are avoided. This can be seen at for example "End   |
   of media" event when all media has finished playing, the session      |
   still remain in Play state. An explicit PAUSE request must be sent to |
   change the state to Ready. It may appear that there exist two auto-   |
   matic transitions in "RedP reached" and "PP reached", however they    |
   are requested and acknowledge before they take place. The time at     |
   which the transition will happen is known by looking at the range     |
   header. If the client sends request close in time to these transi-    |
   tions it must be prepared for getting error message as the state may  |
   or may not have changed.                                              |

   SETUP and TEARDOWN requests with media URLs in aggregated sessions    |
   may not be handled by the server as it is optional functionality. Use |
   the service discovery mechanism with OPTIONS to find out in before-   |
   hand if the server implements it. If the functionality is not imple-  |
   mented but still tried by the client a "501 Not Implemented" response
   SHALL be received. |

Action         Requisite          New State  Response
      ------------------------------------------------------------
------------------------------------------------------------------------
PAUSE          PrsURL,No range      Ready
      Out-of-disc                       Record    Stop recording    Set RP to present point
PAUSE          PrsURL,Range>now     Play     Set RP & PP to given point
PAUSE          PrsURL,Range<=now    Ready    Set RP to Range Hdr.
PP reached                          Ready    RP = PP
End of media   All media            Play     No action, RP = Invalid
End of media   >=1 Media plays      Play     No action
End of range                        Play     Set RP = End of range
SETUP          New URL,IFI          Play     NRM+=1, 200, *A
SETUP          New URL              Play     455
SETUP          Setuped URL          Play     455
SETUP          Setuped URL, IFI     Play     Change transport param.
TEARDOWN       URL=*                Init     No session hdr
TEARDOWN       Prs URL,NRM>1        Init     No session hdr
TEARDOWN       md URL,NRM=1,IFI   Ready-nm   Session hdr
TEARDOWN       md URL,NRM>1,IFI   Record     Play     Session hdr
TEARDOWN       md URL             Record    501               Play     455
S->C:REDIRECT  Range hdr          Record            Play     Set RedP
S->C:REDIRECT  w/o  no range hdr         Init     Stop Recording Media Playout
RedP reached                        Init     Stop Recording Media playout
Timeout                             Init     Stop Media playout

   Table 10: State: Record Play, *A: RTP-Info and Range header

   SHALL be received.                                                    |

   The Record state Table 10 11 has only one event which is unique for this |
   table, namely the "out-of-disc" event.  This event will happen if the |
   recording server runs out of disc space. The state machine will       |
   remain in the Record state but the server will not be able to perform |
   the actions related to the state.                                     |

     Something is needed to signal the client the fact that the     |
     server run out of disc space and not was capable of recording  |
     the data sent by the client.                                   |

B Interaction with RTP

   RTSP allows media clients to control selected, non-contiguous sec-
   tions of media presentations, rendering those streams with an RTP
   media layer[23]. The media layer rendering the RTP stream should not
   be affected by jumps in NPT. Thus, both RTP sequence numbers and RTP
      Action         Requisite         New State  Response
      ------------------------------------------------------------
      PAUSE          No range hdr        Ready
      PAUSE          range hdr > now    Record    Set PP
      PAUSE          range hdr <= now    Ready    Set PP
      Out-of-disc                       Record    Stop recording
      TEARDOWN       URL=*               Init     No session hdr
      TEARDOWN       Prs URL,NRM>1       Init     No session hdr
      TEARDOWN       md URL,NRM=1,IFI  Ready-nm   Session hdr
      TEARDOWN       md URL,NRM>1,IFI   Record    Session hdr
      TEARDOWN       md URL             Record    501
      S->C:REDIRECT  Range hdr          Record    Set RedP
      S->C:REDIRECT  w/o range hdr       Init     Stop Recording
      RedP reached                       Init     Stop Recording
      PP reached                         Ready    Stop Recording
      Timeout                            Init

   Table 11: State: Record

   timestamps MUST be continuous and monotonic across jumps of NPT.

   As an example, assume a clock frequency of 8000 Hz, a packetization
   interval of 100 ms and an initial sequence number and timestamp of
   zero.  First we play NPT 10 through 15, then skip ahead and play NPT
   18 through 20. The first segment is presented as RTP packets with
   sequence numbers 0 through 49 and timestamp 0 through 39,200. The
   second segment consists of RTP packets with sequence number 50
   through 69, with timestamps 40,000 through 55,200.

     We cannot assume that the RTSP client can communicate with the
     RTP media agent, as the two may be independent processes. If
     the RTP timestamp shows the same gap as the NPT, the media
     agent will assume that there is a pause in the presentation.
     If the jump in NPT is large enough, the RTP timestamp may roll
     over and the media agent may believe later packets to be
     duplicates of packets just played out.

   For certain datatypes, tight integration between the RTSP layer and
   the RTP layer will be necessary. This by no means precludes the above
   restriction. Combined RTSP/RTP media clients should use the RTP-Info
   field to determine whether incoming RTP packets were sent before or
   after a seek.

   For continuous audio, the server SHOULD set the RTP marker bit at the
   beginning of serving a new PLAY request. This allows the client to
   perform playout delay adaptation.

   For scaling (see Section 12.34), RTP timestamps should correspond to
   the playback timing. For example, when playing video recorded at 30
   frames/second at a scale of two and speed (Section 12.35) of one, the
   server would drop every second frame to maintain and deliver video
   packets with the normal timestamp spacing of 3,000 per frame, but NPT
   would increase by 1/15 second for each video frame.

   The client can maintain a correct display of NPT by noting the RTP
   timestamp value of the first packet arriving after repositioning. The
   sequence parameter of the RTP-Info (Section 12.33) header provides
   the first sequence number of the next segment.

C Use of SDP for RTSP Session Descriptions

   The Session Description Protocol (SDP, RFC 2327 [24]) may be used to
   describe streams or presentations in RTSP.  This description is typi-
   cally returned in reply to a DESCRIBE request on a URL from a server
   to a client, received via HTTP from a server to a client, or sent in
   an ANNOUNCE method from the client to the server.

   This appendix describes how an SDP file determines the operation of
   an RTSP session.  SDP provides no mechanism by which a client can
   distinguish, without human guidance, between several media streams to
   be rendered simultaneously and a set of alternatives (e.g., two audio
   streams spoken in different languages).

C.1 Definitions

   The terms "session-level", "media-level" and other key/attribute
   names and values used in this appendix are to be used as defined in
   SDP (RFC 2327 [24]):

C.1.1 Control URL

   The "a=control:" attribute is used to convey the control URL. This
   attribute is used both for the session and media descriptions. If
   used for individual media, it indicates the URL to be used for con-
   trolling that particular media stream. If found at the session level,
   the attribute indicates the URL for aggregate control.

   control-attribute  =  "a=" "control" ":" url

   Example:

     a=control:rtsp://example.com/foo

   This attribute may contain either relative and absolute URLs, follow-
   ing the rules and conventions set out in RFC 1808 [25]. 2396 [22]. Implementa-
   tions should look for a base URL in the following order:

     1.   the RTSP Content-Base field;

     2.   the RTSP Content-Location field;

     3.   the RTSP request URL.

   If this attribute contains only an asterisk (*), then the URL is
   treated as if it were an empty embedded URL, and thus inherits the
   entire base URL.

   For SDP retrieved from a container file, there are certain things to  |
   consider. Lets say that the container file has the following URL:     |
   "rtsp://example.com/container.mp4". A media level relative URL needs  |
   to contain the file name container.mp4 in the beginning to be         |
   resolved correctly relative to the before given URL. An alternative   |
   if one does not desire to enter the container files name is to ensure |
   that the base URL for the SDP document becomes: "rtsp://exam-         |
   ple.com/container.mp4/", i.e. an extra trailing slash.  When using    |
   the URL resolution rules in RFC 2396 that will resolve correctly.     |
   However as a warning if the session level control URL is a * that     |
   control URL will be equal to "rtsp://example.com/container.mp4/" and  |
   include the slash.                                                    |

C.1.2 Media Streams

   The "m=" field is used to enumerate the streams. It is expected that
   all the specified streams will be rendered with appropriate synchro-
   nization. If the session is unicast, the port number serves as a rec-
   ommendation from the server to the client; the client still has to
   include it in its SETUP request and may ignore this recommendation.
   If the server has no preference, it SHOULD set the port number value
   to zero.

   Example:

     m=audio 0 RTP/AVP 31

C.1.3 Payload Type(s)

   The payload type(s) are specified in the "m=" field. In case the pay-
   load type is a static payload type from RFC 1890 [1], no other infor-
   mation is required. In case it is a dynamic payload type, the media
   attribute "rtpmap" is used to specify what the media is. The "encod-
   ing name" within the "rtpmap" attribute may be one of those specified
   in RFC 1890 (Sections 5 and 6), or an MIME type registered with IANA,
   or an experimental encoding with a "X-" prefix as specified in SDP
   (RFC 2327 [24]). Codec-specific parameters are not specified in this
   field, but rather in the "fmtp" attribute described below.  Implementors Implemen-
   tors seeking to register new encodings should follow the procedure in
   RFC 1890 [1]. If the media type is not suited to the RTP AV profile,
   then it is recommended that a new profile be created and the appropriate appro-
   priate profile name be used in lieu of "RTP/AVP" in the "m=" field.

C.1.4 Format-Specific Parameters

   Format-specific parameters are conveyed using the "fmtp" media
   attribute. The syntax of the "fmtp" attribute is specific to the
   encoding(s) that the attribute refers to. Note that the packetization
   interval is conveyed using the "ptime" attribute.

C.1.5 Range of Presentation

   The "a=range" attribute defines the total time range of the stored    |
   session. (The length of live sessions can be deduced from the "t" and |
   "r" parameters.) Unless the presentation contains media streams of    |
   different durations, the length attribute is a session-level          |
   attribute. In case of different length the range attribute MUST be    |
   given at media level for all media. The unit is specified first, followed fol- |
   lowed by the value range. The units and their values are as defined   |
   in Section 3.4, 3.5 and 3.6. '

   Examples:

     a=range:npt=0-34.4368
     a=range:clock=19971113T2115-19971113T2203

C.1.6 Time of Availability

   The "t=" field MUST contain suitable values for the start and stop
   times for both aggregate and non-aggregate stream control. With
   aggregate control, the server SHOULD indicate a stop time value for
   which it guarantees the description to be valid, and a start time
   that is equal to or before the time at which the DESCRIBE request was
   received. It MAY also indicate start and stop times of 0, meaning
   that the session is always available. With non-aggregate control, the
   values should reflect the actual period for which the session is
   available in keeping with SDP semantics, and not depend on other
   means (such as the life of the web page containing the description)
   for this purpose.

C.1.7 Connection Information

   In SDP, the "c=" field contains the destination address for the media
   stream. However, for on-demand unicast streams and some multicast
   streams, the destination address is specified by the client via the
   SETUP request. Unless the media content has a fixed destination
   address, the "c=" field is to be set to a suitable null value. For
   addresses of type "IP4", this value is "0.0.0.0".

C.1.8 Entity Tag

   The optional "a=etag" attribute identifies a version of the session
   description. It is opaque to the client. SETUP requests may include
   this identifier in the If-Match field (see section 12.22) to only
   allow session establishment if this attribute value still corresponds
   to that of the current description.  The attribute value is opaque
   and may contain any character allowed within SDP attribute values.

   Example:

     a=etag:158bb3e7c7fd62ce67f12b533f06b83a

     One could argue that the "o=" field provides identical func-
     tionality. However, it does so in a manner that would put
     constraints con-
     straints on servers that need to support multiple session
     description types other than SDP for the same piece of media
     content.

C.2 Aggregate Control Not Available

   If a presentation does not support aggregate control and multiple
   media sections are specified, each section MUST have the control URL
   specified via the "a=control:" attribute.

   Example:

   v=0
   o=- 2890844256 2890842807 IN IP4 204.34.34.32
   s=I came from a web page
   c=IN IP4 0.0.0.0
   t=0 0
   m=video 8002 RTP/AVP 31
   a=control:rtsp://audio.com/movie.aud
   m=audio 8004 RTP/AVP 3
   a=control:rtsp://video.com/movie.vid

   Note that the position of the control URL in the description implies
   that the client establishes separate RTSP control sessions to the
   servers audio.com and video.com

   It is recommended that an SDP file contains the complete media ini-
   tialization information even if it is delivered to the media client
   through non-RTSP means. This is necessary as there is no mechanism to
   indicate that the client should request more detailed media stream
   information via DESCRIBE.

C.3 Aggregate Control Available

   In this scenario, the server has multiple streams that can be con-
   trolled as a whole. In this case, there are both a media-level
   "a=control:" attributes, which are used to specify the stream URLs,
   and a session-level "a=control:" attribute which is used as the
   request URL for aggregate control. If the media-level URL is rela-
   tive, it is resolved to absolute URLs according to Section C.1.1
   above.

   If the presentation comprises only a single stream, the media-level
   "a=control:" attribute may be omitted altogether. However, if the
   presentation contains more than one stream, each media stream section
   MUST contain its own "a=control" attribute.

   Example:

   v=0
   o=- 2890844256 2890842807 IN IP4 204.34.34.32
   s=I contain
   i=<more info>
   c=IN IP4 0.0.0.0
   t=0 0
   a=control:rtsp://example.com/movie/
   m=video 8002 RTP/AVP 31
   a=control:trackID=1
   m=audio 8004 RTP/AVP 3
   a=control:trackID=2
   In this example, the client is required to establish a single RTSP
   session to the server, and uses the URLs rtsp://exam-
   ple.com/movie/trackID=1 and rtsp://example.com/movie/trackID=2 to set
   up the video and audio streams, respectively. The URL rtsp://exam-
   ple.com/movie/ controls the whole movie.

   A client is not required to issues SETUP requests for all streams     |
   within an aggregate object. Servers SHOULD allow the client to ask    |
   for only a subset of the streams.

D Minimal RTSP implementation

D.1 Client

   A client implementation MUST be able to do the following :

     + Generate the following requests: SETUP, TEARDOWN, and one of PLAY
       (i.e., a minimal playback client) or RECORD (i.e., a minimal
       recording client). If RECORD is implemented, ANNOUNCE MUST be
       implemented as well.

     + Include the following headers in requests: CSeq, Connection, Ses-
       sion, Transport. If ANNOUNCE is implemented, the capability to
       include headers Content-Language, Content-Encoding, Content-
       Length, and Content-Type should be as well.

     + Parse and understand the following headers in responses: CSeq,
       Connection, Session, Transport, Content-Language, Content-Encod-
       ing, Content-Length, Content-Type. If RECORD is implemented, the
       Location header must be understood as well. RTP-compliant imple-
       mentations should also implement RTP-Info.

     + Understand the class of each error code received and notify the
       end-user, if one is present, of error codes in classes 4xx and
       5xx. The notification requirement may be relaxed if the end-user
       explicitly does not want it for one or all status codes.

     + Expect and respond to asynchronous requests from the server, such
       as ANNOUNCE. This does not necessarily mean that it should imple-
       ment the ANNOUNCE method, merely that it MUST respond positively
       or negatively to any request received from the server.

   Though not required, the following are RECOMMENDED. RECOMMENDED.

     + Implement RTP/AVP/UDP as a valid transport.

     + Inclusion of the User-Agent header.

     + Understand SDP session descriptions as defined in Appendix C

     + Accept media initialization formats (such as SDP) from standard
       input, command line, or other means appropriate to the operating
       environment to act as a "helper application" for other applica-
       tions (such as web browsers).

     There may be RTSP applications different from those initially
     envisioned by the contributors to the RTSP specification for
     which the requirements above do not make sense. Therefore, the
     recommendations above serve only as guidelines instead of
     strict requirements.

D.1.1 Basic Playback

   To support on-demand playback of media streams, the client MUST addi-
   tionally be able to do the following:

     + generate the PAUSE request;

     + implement the REDIRECT method, and the Location header.

D.1.2 Authentication-enabled

   In order to access media presentations from RTSP servers that require
   authentication, the client MUST additionally be able to do the fol-
   lowing:

     + recognize the 401 (Unauthorized) status code;

     + parse and include the WWW-Authenticate header;

     + implement Basic Authentication and Digest Authentication.

D.2 Server

   A minimal server implementation MUST be able to do the following:

     + Implement the following methods: SETUP, TEARDOWN, OPTIONS and
       either PLAY (for a minimal playback server) or RECORD (for a min-
       imal recording server).

       If RECORD is implemented, ANNOUNCE SHOULD be implemented as well.

     + Include the following headers in responses: Connection, Content-  |
       Length, Content-Type, Content-Language, Content-Encoding,         |
       Timestamp, Transport, Public, and Via, and Unsupported. The capa- |
       bility to include the Location header SHOULD be implemented if    |
       the RECORD method is. RTP-compliant implementations MUST also     |
       implement the RTP-Info field.                                     |

     + Parse and respond appropriately to the following headers in       |
       requests: Connection, Proxy-Require, Session, Transport, and      |
       Require.                                                          |

   Though not required, the following are highly recommended at the time
   of publication for practical interoperability with initial implemen-
   tations and/or to be a "good citizen".

     + Implement RTP/AVP/UDP as a valid transport.

     + Inclusion of the User-Agent Server header.

     + Understand Implement the DESCRIBE method.

     + Generate SDP session descriptions as defined in Appendix C

     + Accept media initialization formats (such as SDP) from standard
       input, command line, or other means appropriate to the operating
       environment to act as a "helper application" for other applica-
       tions (such as web browsers).

     There may be RTSP applications different from those initially
     envisioned by the contributors to the RTSP specification for
     which the requirements above do not make sense. Therefore, the
     recommendations above serve only as guidelines instead of
     strict requirements.

D.1.1

D.2.1 Basic Playback

   To support on-demand playback of media streams, the client server MUST addi-
   tionally be able to do the following:

     + generate Recognize the Range header, and return an error if seeking is not
       supported.

     + Implement the PAUSE request; method.

   In addition, in order to support commonly-accepted user interface
   features, the following are highly recommended for on-demand media
   servers:

     + implement Include and parse the REDIRECT method, Range header, with NPT units. Implementa-
       tion of SMPTE units is recommended.

     + Include the length of the media presentation in the media ini-
       tialization information.

     + Include mappings from data-specific timestamps to NPT. When RTP
       is used, the rtptime portion of the RTP-Info field may be used to
       map RTP timestamps to NPT.

     Client implementations may use the presence of length informa-
     tion to determine if the clip is seekable, and visably disable
     seeking features for clips for which the length information is
     unavailable. A common use of the presentation length is to
     implement a "slider bar" which serves as both a progress indi-
     cator and a timeline positioning tool.

   Mappings from RTP timestamps to NPT are necessary to ensure correct
   positioning of the Location header.

D.1.2 slider bar.

D.2.2 Authentication-enabled

   In order to access media presentations correctly handle client authentication, the server MUST
   additionally be able to do the following:

     + Generate the 401 (Unauthorized) status code when authentication
       is required for the resource.

     + Parse and include the WWW-Authenticate header

     + Implement Basic Authentication and Digest Authentication

E Open Issues

     1.   Define text/parameter MIME type in this spec or separate
          draft.

     2.   Define how to use feature tags.

     3.   Clarify the usage of parameters

     4.   Should we add the header Accept-Ranges as proposed in this
          specification?

     5.   Upon receiving a response on a REDIRECT request can the server
          close the session or should it wait for a TEARDOWN request
          from the client?

     6.   The proxy indications in the two header tables in chapter 12
          needs review.

     7.   Shall transport security (TLS) be added, some small part are
          in here. It might be best to write up a separate draft on
          this.

     8.   Should the 304 status code be allowed?

     9.   Shall we allow usage of range for live content at all. Can be
          used to specify when media delivery starts and stops.  Espe-
          cially for multiple ranges.

     10.  How shall RECORD be done. Interaction with ANNOUNCE, error
          messages. More usage details must be added to make it a solid
          specification.

     11.  Should the Allow header be possible to use optional in request
          or responses besides the now specified 405 error code?

     12.  What text should be written on use of authorization in this
          spec?

     13.  How does entity tags relate to the If-Match header? The usage
          in SDP must also be clarified related to syntax, etc.

     14.  Should the Last-Modified header be required on other level
          than optional?

     15.  How to handle range headers for negative scale playback.

     16.  Write a chapter on how rtspu works and what is required to
          implement for that functionality.

     17.  Must not the sender of a request include it self in a via
          header? Otherwise the first proxy needs to remember where the
          request came from RTSP servers and when receiving response resolve that.
          Seems simpler that require
   authentication, the client MUST additionally be able to do the fol-
   lowing:

     + recognize request when reaching the 401 (Unauthorized) status code;
     + parse and include server con-
          tains all nodes that has touched the WWW-Authenticate header;

     + implement Basic Authentication and Digest Authentication.

D.2 Server

   A message.

     18.  The minimal server implementation MUST must be able looked over to do the following:

     + Implement see if it
          complies with the following methods: SETUP, TEARDOWN, OPTIONS specification. All must and
       either PLAY (for a minimal playback server) or RECORD (for a min-
       imal recording server).

       If RECORD is implemented, ANNOUNCE SHOULD should shall be implemented as well.

     + Include
          included in the following headers minimal. Option-tags for these needs to be
          defined. Further option tags needs to be discussed.

     19.  A RTSP MIB should be defined in responses: Connection, Content-
       Length, Content-Type, Content-Language, Content-Encoding, Trans-
       port, Public. a separate document.

     20.  The capability list specifying which status codes are allowed on which
          request methods seem to include be in error and need review.

F Changes
   Compared to RFC 2326, the Location following issues are addressed:

     + http://rtsp.org/bug448521 - "URLs in Rtp-Info need to be quoted".
       URLs in RTP-info header
       should now MAY be implemented quoted if the RECORD method is. RTP-compliant
       implementations needed.

     + http://rtsp.org/bug448525 - Syntax for SSRC should also implement the RTP-Info field. be clarified.
       Require 8*8 HEX and corresponding text added.

     + Parse http://rtsp.org/bug461083 - "Body w/o Content-Length clarifica-
       tion". This is clarified and respond appropriately any message with a message body is
       required to have a Content-Length header.

     + http://rtsp.org/bug477407 - Transport BNF doesn't properly deal
       with semicolon and comma

     + http://rtsp.org/bug477413 - Transport BNF: mode parameter issues

     + http://rtsp.org/bug477416 - "BNF error section 3.6 NPT", Added an
       optional [NPT] definition. Fixed so that the following headers same possibilities
       exist for all time formats.

     + http://rtsp.org/bug477421 - "When to send response". A clarifying
       note in
       requests: Connection, Session, Transport, Require.

   Though not required, the following are highly recommended at status code chapter that when sending 400 responses,
       the time
   of publication for practical interoperability with initial implemen-
   tations and/or to be a "good citizen".

     + Implement RTP/AVP/UDP as a valid transport. server MUST NOT add cseq if missing.

     + Inclusion http://rtsp.org/bug507347 - Removal of destination redirection in
       the Server transport header.

     + Implement http://rtsp.org/bug477404 - "Errors in table in chapter 12".  The
       table has been updated using the DESCRIBE method. SIP structure. However the table
       become to big to fit in a single page and has been split.

     + Generate SDP session descriptions as defined http://rtsp.org/bug477419 - Updating HTTP references to rfc2616
       by adding public, and content-base header. Section references in Appendix C

     There may be
       header chapter updated. Known effects on RTSP applications different from those initially
     envisioned by the contributors due to HTTP clari-
       fications:

       - Content-Encoding header can include encoding of type "iden-
         tity".

     + http://rtsp.org/bug500803 - Rewritten the RTSP specification for
     which complete chapter on the requirements above do not make sense. Therefore,
       state machine.

     + http://rtsp.org/bug513753 - Created a IANA section defining four
       registries.

     + http://rtsp.org/bug477427 - A new subsection in the
     recommendations above serve only connections
       chapter clarifying how the server and client may handle transport
       connections. Includes defining a feature tag.

     + - Accept-Ranges response header is added. This header clarifies
       which range formats that can be used for a resource.

     + - Added Headers Timestamp, Via, Unsupported as guidelines instead of
     strict requirements.

D.2.1 Basic Playback

   To support on-demand playback of media streams, required for a
       minimal server implementation.

     + http://rtsp.org/bug477425 - "Inconsistency between timeformats".
       Fixed so that all formats has the server MUST addi-
   tionally be able same capabilities as NPT.

     + http://rtsp.org/bug499573 - "Incorrect grammar on Server header".
       Added corrected BNF for User-Agent and Server header as a comple-
       ment to do the following: reference.

     + Recognize The definition in the Range header, introduction of the RTSP session has been
       changed.

     + Updated RTSP URL's and return an error if seeking is not
       supported. source and destination parameters in the
       transport header to handle IPv6 addresses.

     + Implement All BNF definitions are updated according to the PAUSE method.

   In addition, rules defined in order
       RFC 2234 [14].

     + The use of status code 303 "See Other" has been decapitated as it
       does not make sense to support commonly-accepted user interface
   features, the following are highly recommended for on-demand media
   servers: use in RTSP.

     + Include Added status code 350, 351 and parse updated usage of the Range header, with NPT units. Implementa-
       tion other redi-
       rect status codes, see chapter  11.3.

     + Removed Queued play (http://rtsp.org/bug508211) and decapitated
       use of SMPTE units is recommended. PLAY for keep-alive while in playing state.

     + Include Explicitly wrote out the length possibilities to use multiple ranges to
       allow for editing.

     + Text specifying the special behavior of PLAY for live content.

     + When sending response 451 and 458 the media presentation in response body should con-
       tain the media ini-
       tialization information. offending parameters.

     + Include mappings from data-specific timestamps to NPT. When RTP
       is used, Fixed the rtptime portion of missing definitions for the RTP-Info field may be used to
       map RTP timestamps Cache-Control header.  Also
       added to NPT.

     Client implementations may use the presence syntax definition the missing delta-seconds for max-
       stale and min-fresh parameters.

     + Added wording on the usage of length informa-
     tion to determine if Connection:Close for RTSP.

     + Put requirement on CSeq header that the clip value is seekable, and visably disable
     seeking features increased by one
       for clips each new RTSP request.

     + Added requirement that the Date header must be used for which all mes-
       sages with entity. Also the length information is
     unavailable. A common Server should always include it.

     + Removed possibility to use of the presentation length is Range header combined with Scale
       header to
     implement a "slider bar" which serves indicate when it shall be activated, due to that it
       can't work as both a progress indi-
     cator defined. Also added rule that lack of scale header
       in response indicate lack of support. Option tags for scaled
       playback and a timeline positioning tool.

   Mappings from RTP timestamps to NPT are necessary recording defined.

     + The Speed header must now be responded to ensure correct
   positioning of indicate support and
       the slider bar.

D.2.2 Authentication-enabled

   In order actual speed going to correctly handle client authentication, the server MUST
   additionally be able to do the following:

     + Generate the 401 (Unauthorized) status code when authentication used. A option-tag is required for defined.
       Notes on congestion control was also added.

     + The Supported header was borrowed from SIP to help with the resource.
       option negotiation in RTSP.

     + Parse and include Clarified that the WWW-Authenticate timestamp header can be used to resolve
       retransmission ambiguities.

     + Implement Basic Authentication Added two transport header parameters to be used to signal RTCP
       port for server and Digest Authentication

E Changes

   Since RFC 2326, the following issues were addressed:

     + http://rtsp.org/bug448521 - URLs client when not assigned in Rtp-Info need to pairs. Shall be quoted
       used for NAT traversal with mechanisms like STUN. The interoper-
       ability issue is solved by requiring a client to know that a
       server supports this specification.

     + http://rtsp.org/bug448525 - Syntax Defined a IANA registries for SSRC should be the transport headers parameters,
       transport-protocol, profile, lower-transport, and mode.

     + The OPTIONS method has been clarified on how to use the Public
       and Allow headers.

     + http://rtsp.org/bug461083 - Body w/o Content-Length clarification

     + http://rtsp.org/bug477407 - Transport BNF doesn't properly deal The Session header text has been expanded with semicolon a explanation on
       keep alive and comma

     + http://rtsp.org/bug477413 - Transport BNF: mode parameter issues

     + http://rtsp.org/bug477416 - BNF error section 3.6 NPT

     + http://rtsp.org/bug477421 - When which methods to send response

     + http://rtsp.org/bug507347 - Removal of destination redirection use.

     + http://rtsp.org/bug477404 http://rtsp.org/bug503949 - Expanded the table Range header format for PAUSE is
       unclear. This has been resolved by requiring a ranged pause to something use-
       ful, proxy indications still missing.
       only contain a single value as a beginning of an open range.

     + http://rtsp.org/bug477419 - Started updating to rfc2616 by adding
       public header. Section references Servers may optional implement SETUP and TEARDOWN of a single
       media while in header chapter needs update. PLAY state. This is signaled using an option tag
       (play.setup).

     + http://rtsp.org/bug500803 - Rewritten the complete chapter The transport headers interleave parameter's text was made more
       strict and use formal requirements levels. However no change on the
       state machine. Needs review.

     + http://rtsp.org/bug513753 - Created a IANA section defining four
       registries.
       how it is used was made.

   Note that this list does not reflect minor changes in wording or cor-
   rection of typographical errors.

   A word-by-word diff from RFC 2326 can be found at
   http://rtsp.org/2002/drafts

F

G Author Addresses

   Henning Schulzrinne
   Dept. of Computer Science
   Columbia University
   1214 Amsterdam Avenue
   New York, NY 10027
   USA
   electronic mail: schulzrinne@cs.columbia.edu

   Anup Rao
   Cisco
   USA
   electronic mail: anrao@cisco.com

   Robert Lanphier
   RealNetworks
   P.O. Box 91123
   Seattle, WA 98111-9223
   USA
   electronic mail: robla@real.com

   Magnus Westerlund
   Ericsson AB, ERA/TVA/A
   Torshamsgatan 23
   SE-164 80 STOCKHOLM
   SWEDEN
   electronic mail: magnus.westerlund@ericsson.com

G

H Acknowledgements

   This draft is based on the functionality of the original RTSP draft
   submitted in October 1996. It also borrows format and descriptions
   from HTTP/1.1.

   This document has benefited greatly from the comments of all those
   participating in the MMUSIC-WG. In addition to those already men-
   tioned, the following individuals have contributed to this specifica-
   tion:

   Rahul Agarwal, Jeff Ayars, Milko Boic, Torsten Braun, Brent Browning,
   Bruce Butterfield, Steve Casner, Francisco Cortes, Kelly Djahandari,
   Martin Dunsmuir, Eric Fleischman, Jay Geagan, Andy Grignon, V.
   Guruprasad, Peter Haight, Mark Handley, Brad Hefta-Gaub, Volker Hilt,
   John K. Ho, Philipp Hoschka, Anne Jones, Anders Klemets, Ruth Lang,
   Stephanie Leif, Jonathan Lennox, Eduardo F. Llach, Thomas Marshall,
   Rob McCool, Aravind Narasimhan, David Oran, Joerg Ott, Maria
   Papadopouli, Sujal Patel, Ema Patki, Alagu Periyannan, Colin Perkins,
   Igor Plotnikov, Jonathan Sergent, Pinaki Shah, David Singer, Jeff
   Smith, Alexander Sokolsky, Dale Stammen, John Francis Stracke, and
   David Walker.

   [1] H. Schulzrinne, "RTP profile for audio and video conferences with
   minimal control," RFC 1890, Internet Engineering Task Force, Jan.
   1996.

   [2] R. Fielding, J. Gettys, J. Mogul, H. Nielsen, and T. Berners-Lee,
   "Hypertext transfer protocol -- HTTP/1.1," RFC 2068, Internet Engi-
   neering Task Force, Jan. 1997.

   [3] F. Yergeau, G. Nicol, G. Adams, and M. Duerst, "Internationaliza-
   tion of the hypertext markup language," RFC 2070, Internet Engineer-
   ing Task Force, Jan.  1997.

   [4] S. Bradner, "Key words for use in RFCs to indicate requirement
   levels," RFC 2119, Internet Engineering Task Force, Mar. 1997.

   [5] ISO/IEC, "Information technology -- generic coding of moving pic-
   tures and associated audio informaiton -- part 6: extension for digi-
   tal storage media and control," Draft International Standard ISO
   13818-6, International Organization for Standardization ISO/IEC
   JTC1/SC29/WG11, Geneva, Switzerland, Nov. 1995.

   [6] J. Franks, P. Hallam-Baker, and J. Hostetler, "An extension to
   HTTP: digest access authentication," RFC 2069, Internet Engineering
   Task Force, Jan.  1997.

   [7] J. Postel, "User datagram protocol," RFC STD 6, 768, Internet
   Engineering Task Force, Aug. 1980.

   [8] B. Hinden and C. Partridge, "Version 2 of the reliable data pro-
   tocol (RDP)," RFC 1151, Internet Engineering Task Force, Apr. 1990.

   [9] J. Postel, "Transmission control protocol," RFC STD 7, 793,
   Internet Engineering Task Force, Sept. 1981.

   [10] H. Schulzrinne, "A comprehensive multimedia control architecture
   for the Internet," in Proc. International Workshop on Network and
   Operating System Support for Digital Audio and Video (NOSSDAV), (St.
   Louis, Missouri), May 1997.

   [11] P. McMahon, "GSS-API authentication method for SOCKS version 5,"
   RFC 1961, Internet Engineering Task Force, June 1996.

   [12] J. Miller, P. Resnick, and D. Singer, "Rating services and rat-
   ing systems (and their machine readable descriptions)," Recommenda-
   tion REC-PICS-services-961031, W3C (World Wide Web Consortium),
   Boston, Massachusetts, Oct. 1996.

   [13] J. Miller, T. Krauskopf, P. Resnick, and W. Treese, "PICS label
   distribution label syntax and communication protocols," Recommenda-
   tion REC-PICS-labels-961031, W3C (World Wide Web Consortium), Boston,
   Massachusetts, Oct. 1996.

   [14] D. Crocker and P. Overell, "Augmented BNF for syntax specifica-
   tions: ABNF," RFC 2234, Internet Engineering Task Force, Nov. 1997.

   [15] B. Braden, "Requirements for internet hosts - application and
   support," RFC STD 3, 1123, Internet Engineering Task Force, Oct.
   1989.

   [16] R. Elz, "A compact representation of IPv6 addresses," RFC 1924,
   Internet Engineering Task Force, Apr. 1996.

   [17] T. Berners-Lee, L. Masinter, and M. McCahill, "Uniform resource
   locators (URL)," RFC 1738, Internet Engineering Task Force, Dec.
   1994.

   [18] F. Yergeau, "UTF-8, a transformation format of ISO 10646," RFC
   2279, Internet Engineering Task Force, Jan. 1998.

   [19] B. Braden, "T/TCP -- TCP extensions for transactions functional
   specification," RFC 1644, Internet Engineering Task Force, July 1994.

   [20] W. R. Stevens, TCP/IP illustrated: the implementation, vol. 2.
   Reading, Massachusetts: Addison-Wesley, 1994.

   [21] H. Schulzrinne, R. Lanphier, and A. Rao, "Real time streaming
   protocol (RTSP)," RFC 2326, Internet Engineering Task Force, Apr.
   1998.

   [22] T. Berners-Lee, R. Fielding, and L. Masinter, "Uniform resource
   identifiers (URI): generic syntax," RFC 2396, Internet Engineering
   Task Force, Aug. 1998.

   [23] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson, "RTP:
   a transport protocol for real-time applications," RFC 1889, Internet
   Engineering Task Force, Jan. 1996.

   [24] M. Handley and V. Jacobson, "SDP: session description protocol,"
   RFC 2327, Internet Engineering Task Force, Apr. 1998.

   [25] R. Fielding, "Relative uniform resource locators," RFC 1808,
   Internet Engineering Task Force, June 1995.

   [26] R. Fielding, "Hypertext Transfer Protocol -- HTTP/1.1," RFC
   2616, Internet Engineering Task Force, June 1999.

   [27] T. Dierks, C. Allen, "The TLS Protocol, Version 1.0," RFC 2246,
   Internet Engineering Task Force, Januari 1999.

   [28] International Telecommunication Union, "Visual telephone systems
   and equipment for local area networks which provide a non-guaranteed
   quality of service," Recommendation H.323, Telecommunications Stan-
   darization Sector of ITU, Geneva, Switzerland, May 1996.

   [29] T. Narten, H. Alvestrand, "Guidelines for Writing an IANA Con-
   siderations Section in RFCs," RFC2434, Internet Engineering Task
   Force, October 1998.

   [30] R. Hinden, B. Carpenter, L. Masinter, "Format for Literal IPv6
   Addresses in URL's," RFC 2732, Internet Engineering Task Force,
   December 1999.

   [31] J. Rosenberg, J. Weinberger, C. Huitema, R. Mahy, "STUN - Simple
   Traversal of UDP Through Network Address Translators," Internet Engi-
   neering Task Force, Work in Progress, October 2002.

   [32] P. Srisuresh, K. Egevang, "Traditional IP Network Address Trans-
   lator (Traditional NAT)," RFC 3022, Internet Engineering Task Force,
   January 2001.

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                           Table of Contents

1          Introduction  . . . . . . . . . . . . . . . . . . . . . .   3
1.1        Purpose   3
1.1        The Update of the Specification . . . . . . . . . . . . .   3
1.2        Purpose . . . . . . . . . . . . . . . . . . . . . . . . .   3
1.3        Requirements  . . . . . . . . . . . . . . . . . . . . . .   5
1.4        Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
1.5        Protocol Properties . . . . . . . . . . . . . . . . . . .   7
1.6        Extending RTSP  . . . . . . . . . . . . . . . . . . . . .   9
1.7        Overall Operation . . . . . . . . . . . . . . . . . . . .  10
1.8        RTSP States . . . . . . . . . . . . . . . . . . . . . . .  11
1.9        Relationship with Other Protocols . . . . . . . . . . . .  12
2          Notational Conventions  . . . . . . . . . . . . . . . . .  12
3          Protocol Parameters . . . . . . . . . . . . . . . . . . .  13
3.1        RTSP Version  . . . . . . . . . . . . . . . . . . . . . .  13
3.2        RTSP URL  . . . . . . . . . . . . . . . . . . . . . . . .  13
3.3        Session Identifiers . . . . . . . . . . . .   3
1.2        Requirements . . . . . . .  14
3.4        SMPTE Relative Timestamps . . . . . . . . . . . . . . .   4
1.3        Terminology .  15
3.5        Normal Play Time  . . . . . . . . . . . . . . . . . . . .  15
3.6        Absolute Time . . . . . . . . . . . . . . . . . . . . . .  16
3.7        Option Tags . . . . . . . . . . . . . . . . . . . . . . .  17
4
1.4        Protocol Properties          RTSP Message  . . . . . . . . . . . . . . . . . . . . . .  17
4.1        Message Types . . . . . . . . . . . . . . . . . . . . . .  18
4.2        Message Headers . . . . . . . . . . . . . . . . . . . . .  18
4.3        Message Body  . . . . . . . . . . . . . . . . . . . . . .  18
4.4        Message Length  . . . . . . . . . . . . . . . . . . . . .  18
5          General Header Fields . . . . . . . . . . . . . . . . . .  19
6
1.5        Extending RTSP          Request . . . . . . . . . . . . . . . . . . . . . . . . .  19
6.1        Request Line  . . . . . . . . . . . . . . . . . . . . . .  19
6.2        Request Header Fields . . . . . . . . . . . . . . . . . .  20
7          Response  . . . . . . . . . . . . . . . . . . . . . . . .  21
7.1        Status-Line . . . . . . . . . . . . . . . . . . . . . . .  21
7.1.1      Status Code and Reason Phrase . . . . . . . . . . . . . .  22
7.1.2      Response Header Fields  . . . . . . . . . . . . . . . . .  24
8          Entity  . . . . . . . . . . . . . . . . . . . . . . . . .  26
8.1        Entity Header Fields  . . . . . . . . . . . . . . . . . .  26
8.2        Entity Body . . . . . . . . . . . . . . . . . . . . . . .  26
9          Connections . . . . . . . . . . . . . . . . . . . . . . .  27
9.1        Pipelining  . . . . . . . . . . . . . . . . . . . . . . .  27
9.2        Reliability and Acknowledgements  . . . . . . . . . . . .  27
9.3        The usage of connections  . . . .   8
1.6        Overall Operation . . . . . . . . . . . .  28
9.4        TBW . . . . . . . .   9
1.7        RTSP States . . . . . . . . . . . . . . . . . . .  29
9.5        Use of IPv6 . . . .  10
1.8        Relationship with Other Protocols . . . . . . . . . . . .  11
2          Notational Conventions . . . . . . .  29
10         Method Definitions  . . . . . . . . . .  11
3          Protocol Parameters . . . . . . . . .  30
10.1       OPTIONS . . . . . . . . . .  12
3.1        RTSP Version . . . . . . . . . . . . . . .  30
10.2       DESCRIBE  . . . . . . .  12
3.2        RTSP URL . . . . . . . . . . . . . . . . .  31
10.3       ANNOUNCE  . . . . . . .  12
3.3        Session Identifiers . . . . . . . . . . . . . . . . .  33

10.4       SETUP . .  13
3.4        SMPTE Relative Timestamps . . . . . . . . . . . . . . . .  14
3.5        Normal Play Time . . . . . . . .  34
10.5       PLAY  . . . . . . . . . . . .  14
3.6        Absolute Time . . . . . . . . . . . . . .  35
10.6       PAUSE . . . . . . . .  15
3.7        Option Tags . . . . . . . . . . . . . . . . . .  39
10.7       TEARDOWN  . . . . .  16
3.7.1      Registering New Option Tags with IANA . . . . . . . . . .  16
4          RTSP Message . . . . . . . . .  41
10.8       GET_PARAMETER . . . . . . . . . . . . .  17
4.1        Message Types . . . . . . . . .  42
10.9       SET_PARAMETER . . . . . . . . . . . . .  17
4.2        Message Headers . . . . . . . . .  42
10.10      REDIRECT  . . . . . . . . . . . .  17
4.3        Message Body . . . . . . . . . . . .  44
10.11      RECORD  . . . . . . . . . .  17
4.4        Message Length . . . . . . . . . . . . . . .  45
10.12      PING  . . . . . .  17
5          General Header Fields . . . . . . . . . . . . . . . . . .  18
6          Request . .  45
10.13      Embedded (Interleaved) Binary Data  . . . . . . . . . . .  46
11         Status Code Definitions . . . . . . . . . . . .  18
6.1        Request Line . . . . .  47
11.1       Success 1xx . . . . . . . . . . . . . . . . .  19
6.2        Request Header Fields . . . . . .  47
11.1.1     100 Continue  . . . . . . . . . . . .  19
7          Response . . . . . . . . . .  47
11.2       Success 2xx . . . . . . . . . . . . . .  20
7.1        Status-Line . . . . . . . . .  48
11.2.1     250 Low on Storage Space  . . . . . . . . . . . . . .  20
7.1.1      Status Code and Reason Phrase . .  48
11.3       Redirection 3xx . . . . . . . . . . . .  21
7.1.2      Response Header Fields . . . . . . . . .  48
11.3.1     TBW . . . . . . . .  23
8          Entity . . . . . . . . . . . . . . . . . . .  48
11.3.2     301 Moved Permanently . . . . . .  25
8.1        Entity Header Fields . . . . . . . . . . . .  48
11.3.3     302 Found . . . . . .  25
8.2        Entity Body . . . . . . . . . . . . . . . . . .  48
11.3.4     303 See Other . . . . .  25
9          Connections . . . . . . . . . . . . . . . . .  48
11.3.5     To be decided on  . . . . . .  26
9.1        Pipelining . . . . . . . . . . . . . .  48
11.3.6     305 Use Proxy . . . . . . . . .  26
9.2        Reliability and Acknowledgements . . . . . . . . . . . .  26
10         Method Definitions .  48
11.3.7     350 Going Away  . . . . . . . . . . . . . . . . . .  27
10.1       OPTIONS . . .  49
11.3.8     351 Load Balancing  . . . . . . . . . . . . . . . . . . .  49
11.4       Client Error 4xx  . . . .  27
10.2       DESCRIBE . . . . . . . . . . . . . . . .  49
11.4.1     400 Bad Request . . . . . . . .  28
10.3       ANNOUNCE . . . . . . . . . . . . .  49
11.4.2     405 Method Not Allowed  . . . . . . . . . . .  30
10.4       SETUP . . . . . .  49
11.4.3     451 Parameter Not Understood  . . . . . . . . . . . . . .  49
11.4.4     452 reserved  . . . . . .  31
10.5       PLAY . . . . . . . . . . . . . . . .  50
11.4.5     453 Not Enough Bandwidth  . . . . . . . . . .  32
10.6       PAUSE . . . . . .  50
11.4.6     454 Session Not Found . . . . . . . . . . . . . . . . . .  50
11.4.7     455 Method Not Valid in This State  . .  34

10.7       TEARDOWN . . . . . . . . .  50
11.4.8     456 Header Field Not Valid for Resource . . . . . . . . .  50
11.4.9     457 Invalid Range . . . . . .  36
10.8       GET_PARAMETER . . . . . . . . . . . . . .  50
11.4.10    458 Parameter Is Read-Only  . . . . . . . .  36
10.9       SET_PARAMETER . . . . . . .  50
11.4.11    459 Aggregate Operation Not Allowed . . . . . . . . . . .  50
11.4.12    460 Only Aggregate Operation Allowed  . . . .  37
10.10      REDIRECT . . . . . .  51
11.4.13    461 Unsupported Transport . . . . . . . . . . . . . . . .  51
11.4.14    462 Destination Unreachable . .  38
10.11      RECORD . . . . . . . . . . . . .  51
11.5       Server Error 5xx  . . . . . . . . . . . .  39
10.12      PING . . . . . . . .  51
11.5.1     551 Option not supported  . . . . . . . . . . . . . . . .  51
12         Header Field Definitions  . .  39
10.13      Embedded (Interleaved) Binary Data . . . . . . . . . . .  40
11         Status Code Definitions . . .  51
12.1       Accept  . . . . . . . . . . . . . .  41
11.1       Success 2xx . . . . . . . . . . .  53
12.2       Accept-Encoding . . . . . . . . . . . .  41
11.1.1     250 Low on Storage Space . . . . . . . . .  55
12.3       Accept-Language . . . . . . .  41
11.2       Redirection 3xx . . . . . . . . . . . . . .  55
12.4       Accept-Ranges . . . . . . .  41
11.3       Client Error 4xx . . . . . . . . . . . . . . .  55
12.5       Allow . . . . .  41
11.4       400 Bad Request . . . . . . . . . . . . . . . . . . . . .  42
11.4.1     405 Method Not Allowed  57
12.6       Authorization . . . . . . . . . . . . . . . . .  42
11.4.2     451 Parameter Not Understood . . . . .  58

12.7       Bandwidth . . . . . . . . .  42
11.4.3     452 reserved . . . . . . . . . . . . . . .  58
12.8       Blocksize . . . . . . .  42
11.4.4     453 Not Enough Bandwidth . . . . . . . . . . . . . . . .  42
11.4.5     454 Session Not Found .  58
12.9       Cache-Control . . . . . . . . . . . . . . . . .  42
11.4.6     455 Method Not Valid in This State . . . . .  58
12.10      Connection  . . . . . .  42
11.4.7     456 Header Field Not Valid for Resource . . . . . . . . .  42
11.4.8     457 Invalid Range . . . . . . . .  61
12.11      Content-Base  . . . . . . . . . . . .  43
11.4.9     458 Parameter Is Read-Only . . . . . . . . . .  61
12.12      Content-Encoding  . . . . .  43
11.4.10    459 Aggregate Operation Not Allowed . . . . . . . . . . .  43
11.4.11    460 Only Aggregate Operation Allowed . . . .  62
12.13      Content-Language  . . . . . .  43
11.4.12    461 Unsupported Transport . . . . . . . . . . . . . .  62
12.14      Content-Length  . .  43
11.4.13    462 Destination Unreachable . . . . . . . . . . . . . . .  43
11.5       Server Error 5xx . . . .  62
12.15      Content-Location  . . . . . . . . . . . . . . . .  43
11.5.1     551 Option not supported . . . .  62
12.16      Content-Type  . . . . . . . . . . . .  43
12         Header Field Definitions . . . . . . . . . .  62
12.17      CSeq  . . . . . .  43
12.1       Accept . . . . . . . . . . . . . . . . . . . .  62
12.18      Date  . . . . .  46
12.2       Accept-Encoding . . . . . . . . . . . . . . . . . . . . .  46
12.3       Accept-Language  63
12.19      Expires . . . . . . . . . . . . . . . . . . . . .  46
12.4       Accept-Ranges . . . .  63
12.20      From  . . . . . . . . . . . . . . . . . .  46
12.5       Allow . . . . . . . .  64
12.21      Host  . . . . . . . . . . . . . . . . . .  48
12.6       Authorization . . . . . . . .  64
12.22      If-Match  . . . . . . . . . . . . . .  48
12.7       Bandwidth . . . . . . . . . .  64
12.23      If-Modified-Since . . . . . . . . . . . . . .  49
12.8       Blocksize . . . . . .  64
12.24      Last-Modified . . . . . . . . . . . . . . . . . .  49
12.9       Cache-Control . . . .  65
12.25      Location  . . . . . . . . . . . . . . . . . .  49
12.10      Connection . . . . . .  65
12.26      Proxy-Authenticate  . . . . . . . . . . . . . . . . .  51
12.11      Content-Base . .  65
12.27      Proxy-Require . . . . . . . . . . . . . . . . . . . .  51
12.12      Content-Encoding . .  65
12.28      Public  . . . . . . . . . . . . . . . . . .  52
12.13      Content-Language . . . . . . .  66
12.29      Range . . . . . . . . . . . . .  52
12.14      Content-Length . . . . . . . . . . . . .  66
12.30      Referer . . . . . . . .  52
12.15      Content-Location . . . . . . . . . . . . . . . . .  67
12.31      Retry-After . . .  52
12.16      Content-Type . . . . . . . . . . . . . . . . . . . .  67
12.32      Require . .  52
12.17      CSeq . . . . . . . . . . . . . . . . . . . . . . .  67
12.33      RTP-Info  . . .  52
12.18      Date . . . . . . . . . . . . . . . . . . . . .  68
12.34      Scale . . . . .  53
12.19      Expires . . . . . . . . . . . . . . . . . . . . .  70
12.35      Speed . . . .  53

12.20      From . . . . . . . . . . . . . . . . . . . . . .  70
12.36      Server  . . . .  54
12.21      Host . . . . . . . . . . . . . . . . . . . . .  71
12.37      Session . . . . .  54
12.22      If-Match . . . . . . . . . . . . . . . . . . . .  71
12.38      Supported . . . .  54
12.23      If-Modified-Since . . . . . . . . . . . . . . . . . . . .  54
12.24      Last-Modified  73
12.39      Timestamp . . . . . . . . . . . . . . . . . . . . . .  55
12.25      Location . .  74
12.40      Transport . . . . . . . . . . . . . . . . . . . . . .  55
12.26      Proxy-Authenticate . .  74
12.41      Unsupported . . . . . . . . . . . . . . . . .  55
12.27      Proxy-Require . . . . . .  78
12.42      User-Agent  . . . . . . . . . . . . . . . .  55
12.28      Public . . . . . . .  79
12.43      Vary  . . . . . . . . . . . . . . . . . .  55
12.29      Range . . . . . . . .  79
12.44      Via . . . . . . . . . . . . . . . . . .  56
12.30      Referer . . . . . . . . .  79
12.45      WWW-Authenticate  . . . . . . . . . . . . . . . .  57
12.31      Retry-After . . . .  79
13         Caching . . . . . . . . . . . . . . . . . . .  57
12.32      Require . . . . . .  79
14         Examples  . . . . . . . . . . . . . . . . . . .  57
12.33      RTP-Info . . . . .  80
14.1       Media on Demand (Unicast) . . . . . . . . . . . . . . . .  80
14.2       Streaming of a Container file . . .  58
12.34      Scale . . . . . . . . . . .  82
14.3       Single Stream Container Files . . . . . . . . . . . . . .  84
14.4       Live Media Presentation Using Multicast .  59
12.35      Speed . . . . . . . .  86
14.5       Recording . . . . . . . . . . . . . . . . . .  60
12.36      Server . . . . . .  87
15         RTSP and NATs . . . . . . . . . . . . . . . . . . .  61
12.37      Session . . .  89
15.1       Introduction  . . . . . . . . . . . . . . . . . . . . . .  61
12.38      Supported  89

15.2       STUN  . . . . . . . . . . . . . . . . . . . . . . . .  61
12.39      Timestamp . .  89
15.3       TBW . . . . . . . . . . . . . . . . . . . . . .  62
12.40      Transport . . . . .  89
15.4       TBW . . . . . . . . . . . . . . . . . . .  62
12.41      Unsupported . . . . . . . .  89
16         Syntax  . . . . . . . . . . . . . . .  66
12.42      User-Agent . . . . . . . . . .  89
16.1       Base Syntax . . . . . . . . . . . . .  66
12.43      Vary . . . . . . . . . .  89
16.2       RTSP Protocol Definition  . . . . . . . . . . . . . . . .  66
12.44      Via  90
17         Security Considerations . . . . . . . . . . . . . . . . .  94
18         IANA Considerations . . . . . . . . . .  66
12.45      WWW-Authenticate . . . . . . . . .  96
18.1       Option-tags . . . . . . . . . . .  66
13         Caching . . . . . . . . . . . .  97
18.1.1     Description . . . . . . . . . . . . .  66
14         Examples . . . . . . . . . .  97
18.1.2     Registering New Option Tags with IANA . . . . . . . . . .  97
18.1.3     Registered entries  . . . .  67
14.1       Media on Demand (Unicast) . . . . . . . . . . . . . . .  98
18.2       RTSP Methods  .  67
14.2       Streaming of a Container file . . . . . . . . . . . . . .  69
14.3       Single Stream Container Files . . . . . . .  98
18.2.1     Description . . . . . . .  72
14.4       Live Media Presentation Using Multicast . . . . . . . . .  74
14.5       Recording . . . . . . .  98
18.2.2     Registering New Methods with IANA . . . . . . . . . . . .  98
18.2.3     Registered Entries  . . . . .  75
15         Syntax . . . . . . . . . . . . . .  99
18.3       RTSP Status Codes . . . . . . . . . . .  76
15.1       Base Syntax . . . . . . . . .  99
18.3.1     Description . . . . . . . . . . . . . .  76
16         Security Considerations . . . . . . . . .  99
18.3.2     Registering New Status Codes with IANA  . . . . . . . .  77
17         IANA Considerations .  99
18.3.3     Registered Entries  . . . . . . . . . . . . . . . . . .  79
17.1       Option-tags .  99
18.4       RTSP Headers  . . . . . . . . . . . . . . . . . . . . . .  80
17.1.1  99
18.4.1     Description . . . . . . . . . . . . . . . . . . . . . . .  80
17.1.2  99
18.4.2     Registering New Option Tags Headers with IANA . . . . . . . . . .  80
17.1.3 . . 100
18.4.3     Registered entries  . . . . . . . . . . . . . . . . . . .  81
17.2       RTSP Methods 100
18.5       Parameters  . . . . . . . . . . . . . . . . . . . . . .  81
17.2.1 . 100
18.5.1     Description . . . . . . . . . . . . . . . . . . . . . . .  81
17.2.2 100
18.5.2     Registering New Methods Parameters with IANA  . . . . . . . . . . . .  81
17.2.3 100
18.5.3     Registered entries  . . . . . . . . . . . . . . . . . . .  81
17.3       RTSP Headers  . . . . . . . . . . . . . . . . . . 101
18.6       MIME type registration  . . . .  82
17.3.1     Description . . . . . . . . . . . . . 101
18.7       Transport Header registries . . . . . . . . . .  82
17.3.2     Registering New Headers with IANA . . . . . 101
18.7.1     Transport Protocols . . . . . . .  82

17.3.3     Registered entries . . . . . . . . . . . . 101
18.7.2     Profile . . . . . . .  82
17.4       Parameters . . . . . . . . . . . . . . . . . . 101
18.7.3     Lower Transport . . . . .  82
17.4.1     Description . . . . . . . . . . . . . . . . 102
18.7.4     Transport modes . . . . . . .  82
17.4.2     Registering New Parameters with IANA . . . . . . . . . .  83
17.4.3     Registered entries . . . . 102
18.8       Cache Directive Extensions  . . . . . . . . . . . . . . .  83 102
A          RTSP Protocol State Machine . . . . . . . . . . . . . . .  83 103
A.1        States  . . . . . . . . . . . . . . . . . . . . . . . . .  83 103
A.2        State variables . . . . . . . . . . . . . . . . . . . . .  84 104
A.3        Abbreviations . . . . . . . . . . . . . . . . . . . . . .  84 104
A.4        State Tables  . . . . . . . . . . . . . . . . . . . . . .  84 104
B          Interaction with RTP  . . . . . . . . . . . . . . . . . .  89 108
C          Use of SDP for RTSP Session Descriptions  . . . . . . . .  90 110
C.1        Definitions . . . . . . . . . . . . . . . . . . . . . . .  90 110
C.1.1      Control URL . . . . . . . . . . . . . . . . . . . . . . .  90 110
C.1.2      Media Streams . . . . . . . . . . . . . . . . . . . . . .  91 111
C.1.3      Payload Type(s) . . . . . . . . . . . . . . . . . . . . .  91 112
C.1.4      Format-Specific Parameters  . . . . . . . . . . . . . . .  91 112
C.1.5      Range of Presentation . . . . . . . . . . . . . . . . . .  91 112

C.1.6      Time of Availability  . . . . . . . . . . . . . . . . . .  92 112
C.1.7      Connection Information  . . . . . . . . . . . . . . . . .  92 113
C.1.8      Entity Tag  . . . . . . . . . . . . . . . . . . . . . . .  92 113
C.2        Aggregate Control Not Available . . . . . . . . . . . . .  93 113
C.3        Aggregate Control Available . . . . . . . . . . . . . . .  93 114
D          Minimal RTSP implementation . . . . . . . . . . . . . . .  94 115
D.1        Client  . . . . . . . . . . . . . . . . . . . . . . . . .  94 115
D.1.1      Basic Playback  . . . . . . . . . . . . . . . . . . . . .  95 116
D.1.2      Authentication-enabled  . . . . . . . . . . . . . . . . .  95 116
D.2        Server  . . . . . . . . . . . . . . . . . . . . . . . . .  96 116
D.2.1      Basic Playback  . . . . . . . . . . . . . . . . . . . . .  96 117
D.2.2      Authentication-enabled  . . . . . . . . . . . . . . . . .  97 118
E          Open Issues . . . . . . . . . . . . . . . . . . . . . . . 118
F          Changes . . . . . . . . . . . . . . . . . . . . . . . . .  97
F 119
G          Author Addresses  . . . . . . . . . . . . . . . . . . . .  98
G 123
H          Acknowledgements  . . . . . . . . . . . . . . . . . . . .  99 123