draft-ietf-mmusic-rfc2326bis-00.txt   draft-ietf-mmusic-rfc2326bis-01.txt 
Internet Engineering Task Force MMUSIC WG Internet Engineering Task Force MMUSIC WG
Internet Draft H. Schulzrinne Internet Draft H. Schulzrinne
Columbia U. Columbia U.
A. Rao A. Rao
Cisco Cisco
R. Lanphier R. Lanphier
RealNetworks RealNetworks
draft-ietf-mmusic-rfc2326bis-00.txt M. Westerlund
February 22, 2002 Ericsson
Expires: July 2002
draft-ietf-mmusic-rfc2326bis-01.txt
June 06, 2002
Expires: December, 2002
Real Time Streaming Protocol (RTSP) Real Time Streaming Protocol (RTSP)
STATUS OF THIS MEMO STATUS OF THIS MEMO
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference mate-
material or to cite them other than as "work in progress". rial or to cite them other than as "work in progress".
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
To view the list Internet-Draft Shadow Directories, see To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
This memorandum is a revision of RFC 2326, which is currently a This memorandum is a revision of RFC 2326, which is currently a Pro-
Proposed Standard. posed Standard.
The Real Time Streaming Protocol, or RTSP, is an application-level The Real Time Streaming Protocol, or RTSP, is an application-level
protocol for control over the delivery of data with real-time protocol for control over the delivery of data with real-time proper-
properties. RTSP provides an extensible framework to enable ties. RTSP provides an extensible framework to enable controlled, on-
controlled, on-demand delivery of real-time data, such as audio and demand delivery of real-time data, such as audio and video. Sources
video. Sources of data can include both live data feeds and stored of data can include both live data feeds and stored clips. This pro-
clips. This protocol is intended to control multiple data delivery tocol is intended to control multiple data delivery sessions, provide
sessions, provide a means for choosing delivery channels such as UDP, a means for choosing delivery channels such as UDP, multicast UDP and
multicast UDP and TCP, and provide a means for choosing delivery TCP, and provide a means for choosing delivery mechanisms based upon
mechanisms based upon RTP (RFC 1889). RTP (RFC 1889).
1 Introduction 1 Introduction
1.1 Purpose 1.1 Purpose
The Real-Time Streaming Protocol (RTSP) establishes and controls The Real-Time Streaming Protocol (RTSP) establishes and controls
either a single or several time-synchronized streams of continuous either a single or several time-synchronized streams of continuous
media such as audio and video. It does not typically deliver the media such as audio and video. It does not typically deliver the con-
continuous streams itself, although interleaving of the continuous tinuous streams itself, although interleaving of the continuous media
media stream with the control stream is possible (see Section 10.12). stream with the control stream is possible (see Section 10.13). In
In other words, RTSP acts as a "network remote control" for other words, RTSP acts as a "network remote control" for multimedia
multimedia servers. servers.
The set of streams to be controlled is defined by a presentation The set of streams to be controlled is defined by a presentation
description. This memorandum does not define a format for a description. This memorandum does not define a format for a presenta-
presentation description. tion description.
There is no notion of an RTSP connection; instead, a server maintains There is no notion of an RTSP connection; instead, a server maintains
a session labeled by an identifier. An RTSP session is in no way tied a session labeled by an identifier. An RTSP session is in no way tied
to a transport-level connection such as a TCP connection. During an to a transport-level connection such as a TCP connection. During an
RTSP session, an RTSP client may open and close many reliable RTSP session, an RTSP client may open and close many reliable trans-
transport connections to the server to issue RTSP requests. port connections to the server to issue RTSP requests. Alternatively,
Alternatively, it may use a connectionless transport protocol such as it may use a connectionless transport protocol such as UDP.
UDP.
The streams controlled by RTSP may use RTP [1], but the operation of The streams controlled by RTSP may use RTP [1], but the operation of
RTSP does not depend on the transport mechanism used to carry RTSP does not depend on the transport mechanism used to carry contin-
continuous media. uous media.
The protocol is intentionally similar in syntax and operation to The protocol is intentionally similar in syntax and operation to
HTTP/1.1 [2] so that extension mechanisms to HTTP can in most cases 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 also be added to RTSP. However, RTSP differs in a number of important
aspects from HTTP: aspects from HTTP:
o RTSP introduces a number of new methods and has a different + RTSP introduces a number of new methods and has a different pro-
protocol identifier. tocol identifier.
o An RTSP server needs to maintain state by default in almost + An RTSP server needs to maintain state by default in almost all
all cases, as opposed to the stateless nature of HTTP. cases, as opposed to the stateless nature of HTTP.
o Both an RTSP server and client can issue requests. + Both an RTSP server and client can issue requests.
o Data is carried out-of-band by a different protocol. (There is + Data is carried out-of-band by a different protocol. (There is an
an exception to this.) exception to this.)
o RTSP is defined to use ISO 10646 (UTF-8) rather than ISO + RTSP is defined to use ISO 10646 (UTF-8) rather than ISO 8859-1,
8859-1, consistent with current HTML internationalization consistent with current HTML internationalization efforts [3].
efforts [3].
o The Request-URI always contains the absolute URI. Because of + The Request-URI always contains the absolute URI. Because of
backward compatibility with a historical blunder, HTTP/1.1 [2] backward compatibility with a historical blunder, HTTP/1.1 [26]
carries only the absolute path in the request and puts the carries only the absolute path in the request and puts the host
host name in a separate header field. name in a separate header field.
This makes "virtual hosting" easier, where a single This makes "virtual hosting" easier, where a single host
host with one IP address hosts several document trees. with one IP address hosts several document trees.
The protocol supports the following operations: The protocol supports the following operations:
Retrieval of media from media server: The client can request a Retrieval of media from media server: The client can request a pre-
presentation description via HTTP or some other method. If sentation description via HTTP or some other method. If the
the presentation is being multicast, the presentation presentation is being multicast, the presentation description
description contains the multicast addresses and ports to contains the multicast addresses and ports to be used for the
be used for the continuous media. If the presentation is continuous media. If the presentation is to be sent only to
to be sent only to the client via unicast, the client the client via unicast, the client provides the destination
provides the destination for security reasons. for security reasons.
Invitation of a media server to a conference: A media server can Invitation of a media server to a conference: A media server can be
be "invited" to join an existing conference, either to play "invited" to join an existing conference, either to play back
back media into the presentation or to record all or a media into the presentation or to record all or a subset of
subset of the media in a presentation. This mode is useful the media in a presentation. This mode is useful for dis-
for distributed teaching applications. Several parties in tributed teaching applications. Several parties in the confer-
the conference may take turns "pushing the remote control ence may take turns "pushing the remote control buttons".
buttons".
Addition of media to an existing presentation: Particularly for Addition of media to an existing presentation: Particularly for
live presentations, it is useful if the server can tell the live presentations, it is useful if the server can tell the
client about additional media becoming available. client about additional media becoming available.
RTSP requests may be handled by proxies, tunnels and caches as in RTSP requests may be handled by proxies, tunnels and caches as in
HTTP/1.1 [2]. HTTP/1.1 [26].
1.2 Requirements 1.2 Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [4]. document are to be interpreted as described in RFC 2119 [4].
1.3 Terminology 1.3 Terminology
Some of the terminology has been adopted from HTTP/1.1 [2]. Terms Some of the terminology has been adopted from HTTP/1.1 [26]. Terms
not listed here are defined as in HTTP/1.1. not listed here are defined as in HTTP/1.1.
Aggregate control: The control of the multiple streams using a Aggregate control: The control of the multiple streams using a sin-
single timeline by the server. For audio/video feeds, this gle timeline by the server. For audio/video feeds, this means
means that the client may issue a single play or pause that the client may issue a single play or pause message to
message to control both the audio and video feeds. control both the audio and video feeds.
Conference: a multiparty, multimedia presentation, where "multi" Conference: a multiparty, multimedia presentation, where "multi"
implies greater than or equal to one. implies greater than or equal to one.
Client: The client requests continuous media data from the media Client: The client requests continuous media data from the media
server. server.
Connection: A transport layer virtual circuit established Connection: A transport layer virtual circuit established between
between two programs for the purpose of communication. two programs for the purpose of communication.
Container file: A file which may contain multiple media streams Container file: A file which may contain multiple media streams
which often comprise a presentation when played together. which often comprise a presentation when played together. RTSP
RTSP servers may offer aggregate control on these files, servers may offer aggregate control on these files, though the
though the concept of a container file is not embedded in concept of a container file is not embedded in the protocol.
the protocol.
Continuous media: Data where there is a timing relationship Continuous media: Data where there is a timing relationship between
between source and sink; that is, the sink must reproduce source and sink; that is, the sink must reproduce the timing
the timing relationship that existed at the source. The relationship that existed at the source. The most common exam-
most common examples of continuous media are audio and ples of continuous media are audio and motion video. Continu-
motion video. Continuous media can be real-time ous media can be real-time (interactive), where there is a
(interactive) , where there is a "tight" timing "tight" timing relationship between source and sink, or
relationship between source and sink, or streaming streaming (playback), where the relationship is less strict.
(playback) , where the relationship is less strict.
Entity: The information transferred as the payload of a request Entity: The information transferred as the payload of a request or
or response. An entity consists of metainformation in the response. An entity consists of metainformation in the form of
form of entity-header fields and content in the form of an entity-header fields and content in the form of an entity-
entity-body, as described in Section 8. body, as described in Section 8.
Media initialization: Datatype/codec specific initialization. Media initialization: Datatype/codec specific initialization. This
This includes such things as clockrates, color tables, etc. includes such things as clockrates, color tables, etc. Any
Any transport-independent information which is required by transport-independent information which is required by a
a client for playback of a media stream occurs in the media client for playback of a media stream occurs in the media ini-
initialization phase of stream setup. tialization phase of stream setup.
Media parameter: Parameter specific to a media type that may be Media parameter: Parameter specific to a media type that may be
changed before or during stream playback. changed before or during stream playback.
Media server: The server providing playback or recording Media server: The server providing playback or recording services
services for one or more media streams. Different media for one or more media streams. Different media streams within
streams within a presentation may originate from different a presentation may originate from different media servers. A
media servers. A media server may reside on the same or a media server may reside on the same or a different host as the
different host as the web server the presentation is web server the presentation is invoked from.
invoked from.
Media server indirection: Redirection of a media client to a Media server indirection: Redirection of a media client to a dif-
different media server. ferent media server.
(Media) stream: A single media instance, e.g., an audio stream (Media) stream: A single media instance, e.g., an audio stream or a
or a video stream as well as a single whiteboard or shared video stream as well as a single whiteboard or shared applica-
application group. When using RTP, a stream consists of all tion group. When using RTP, a stream consists of all RTP and
RTP and RTCP packets created by a source within an RTP RTCP packets created by a source within an RTP session. This
session. This is equivalent to the definition of a DSM-CC is equivalent to the definition of a DSM-CC stream([5]).
stream([5]).
Message: The basic unit of RTSP communication, consisting of a Message: The basic unit of RTSP communication, consisting of a
structured sequence of octets matching the syntax defined structured sequence of octets matching the syntax defined in
in Section 15 and transmitted via a connection or a Section 15 and transmitted via a connection or a connection-
connectionless protocol. less protocol.
Participant: Member of a conference. A participant may be a Participant: Member of a conference. A participant may be a
machine, e.g., a media record or playback server. machine, e.g., a media record or playback server.
Presentation: A set of one or more streams presented to the Presentation: A set of one or more streams presented to the client
client as a complete media feed, using a presentation as a complete media feed, using a presentation description as
description as defined below. In most cases in the RTSP defined below. In most cases in the RTSP context, this implies
context, this implies aggregate control of those streams, aggregate control of those streams, but does not have to.
but does not have to.
Presentation description: A presentation description contains Presentation description: A presentation description contains
information about one or more media streams within a information about one or more media streams within a presenta-
presentation, such as the set of encodings, network tion, such as the set of encodings, network addresses and
addresses and information about the content. Other IETF information about the content. Other IETF protocols such as
protocols such as SDP (RFC 2327 [6]) use the term "session" SDP (RFC 2327 [24]) use the term "session" for a live presen-
for a live presentation. The presentation description may tation. The presentation description may take several differ-
take several different formats, including but not limited ent formats, including but not limited to the session descrip-
to the session description format SDP. tion format SDP.
Response: An RTSP response. If an HTTP response is meant, that Response: An RTSP response. If an HTTP response is meant, that is
is indicated explicitly. indicated explicitly.
Request: An RTSP request. If an HTTP request is meant, that is Request: An RTSP request. If an HTTP request is meant, that is
indicated explicitly. indicated explicitly.
RTSP session: A complete RTSP "transaction", e.g., the viewing RTSP session: A complete RTSP "transaction", e.g., the viewing of a
of a movie. A session typically consists of a client movie. A session typically consists of a client setting up a
setting up a transport mechanism for the continuous media transport mechanism for the continuous media stream (SETUP),
stream ( SETUP), starting the stream with PLAY or RECORD, starting the stream with PLAY or RECORD, and closing the
and closing the stream with TEARDOWN. stream with TEARDOWN.
Transport initialization: The negotiation of transport Transport initialization: The negotiation of transport information
information (e.g., port numbers, transport protocols) (e.g., port numbers, transport protocols) between the client
between the client and the server. and the server.
1.4 Protocol Properties 1.4 Protocol Properties
RTSP has the following properties: RTSP has the following properties:
Extendable: New methods and parameters can be easily added to Extendable: New methods and parameters can be easily added to RTSP.
RTSP.
Easy to parse: RTSP can be parsed by standard HTTP or MIME Easy to parse: RTSP can be parsed by standard HTTP or MIME parsers.
parsers.
Secure: RTSP re-uses web security mechanisms, either at the Secure: RTSP re-uses web security mechanisms, either at the trans-
transport level (TLS, RFC 2246 [7]) or within the protocol port level (TLS, RFC 2246 [27]) or within the protocol itself.
itself. All HTTP authentication mechanisms such as basic All HTTP authentication mechanisms such as basic (RFC 2616
(RFC 2068 [2]) and digest authentication (RFC 2069 [8]) are [26]) and digest authentication (RFC 2069 [6]) are directly
directly applicable. applicable.
Transport-independent: RTSP may use either an unreliable Transport-independent: RTSP may use either an unreliable datagram
datagram protocol (UDP) (RFC 768 [9]), a reliable datagram protocol (UDP) (RFC 768 [7]), a reliable datagram protocol
protocol (RDP, RFC 1151, not widely used [10]) or a (RDP, RFC 1151, not widely used [8]) or a reliable stream pro-
reliable stream protocol such as TCP (RFC 793 [11]) as it tocol such as TCP (RFC 793 [9]) as it implements application-
implements application-level reliability. level reliability.
Multi-server capable: Each media stream within a presentation Multi-server capable: Each media stream within a presentation can
can reside on a different server. The client automatically reside on a different server. The client automatically estab-
establishes several concurrent control sessions with the lishes several concurrent control sessions with the different
different media servers. Media synchronization is media servers. Media synchronization is performed at the
performed at the transport level. transport level.
Control of recording devices: The protocol can control both Control of recording devices: The protocol can control both record-
recording and playback devices, as well as devices that can ing and playback devices, as well as devices that can alter-
alternate between the two modes ("VCR"). nate between the two modes ("VCR").
Separation of stream control and conference initiation: Stream Separation of stream control and conference initiation: Stream con-
control is divorced from inviting a media server to a trol is divorced from inviting a media server to a conference.
conference. The only requirement is that the conference In particular, SIP [10] or H.323 [28] may be used to invite a
initiation protocol either provides or can be used to server to a conference.
create a unique conference identifier. In particular, SIP
[12] or H.323 [13] may be used to invite a server to a
conference.
Suitable for professional applications: RTSP supports frame- Suitable for professional applications: RTSP supports frame-level
level accuracy through SMPTE time stamps to allow remote accuracy through SMPTE time stamps to allow remote digital
digital editing. editing.
Presentation description neutral: The protocol does not impose a Presentation description neutral: The protocol does not impose a
particular presentation description or metafile format and particular presentation description or metafile format and can
can convey the type of format to be used. However, the convey the type of format to be used. However, the presenta-
presentation description must contain at least one RTSP tion description must contain at least one RTSP URI.
URI.
Proxy and firewall friendly: The protocol should be readily Proxy and firewall friendly: The protocol should be readily handled
handled by both application and transport-layer (SOCKS by both application and transport-layer (SOCKS [11]) fire-
[14]) firewalls. A firewall may need to understand the walls. A firewall may need to understand the SETUP method to
SETUP method to open a "hole" for the UDP media stream. open a "hole" for the UDP media stream.
HTTP-friendly: Where sensible, RTSP reuses HTTP concepts, so HTTP-friendly: Where sensible, RTSP reuses HTTP concepts, so that
that the existing infrastructure can be reused. This the existing infrastructure can be reused. This infrastructure
infrastructure includes PICS (Platform for Internet Content includes PICS (Platform for Internet Content Selection
Selection [15,16]) for associating labels with content. [12,13]) for associating labels with content. However, RTSP
However, RTSP does not just add methods to HTTP since the does not just add methods to HTTP since the controlling
controlling continuous media requires server state in most continuous media requires server state in most cases.
cases.
Appropriate server control: If a client can start a stream, it Appropriate server control: If a client can start a stream, it must
must be able to stop a stream. Servers should not start be able to stop a stream. Servers should not start streaming
streaming to clients in such a way that clients cannot stop to clients in such a way that clients cannot stop the stream.
the stream.
Transport negotiation: The client can negotiate the transport Transport negotiation: The client can negotiate the transport
method prior to actually needing to process a continuous method prior to actually needing to process a continuous media
media stream. stream.
Capability negotiation: If basic features are disabled, there Capability negotiation: If basic features are disabled, there must
must be some clean mechanism for the client to determine be some clean mechanism for the client to determine which
which methods are not going to be implemented. This allows methods are not going to be implemented. This allows clients
clients to present the appropriate user interface. For to present the appropriate user interface. For example, if
example, if seeking is not allowed, the user interface must seeking is not allowed, the user interface must be able to
be able to disallow moving a sliding position indicator. disallow moving a sliding position indicator.
An earlier requirement in RTSP was multi-client capability. An earlier requirement in RTSP was multi-client capability.
However, it was determined that a better approach was to However, it was determined that a better approach was to make
make sure that the protocol is easily extensible to the sure that the protocol is easily extensible to the multi-
multi-client scenario. Stream identifiers can be used by client scenario. Stream identifiers can be used by several
several control streams, so that "passing the remote" would control streams, so that "passing the remote" would be possi-
be possible. The protocol would not address how several ble. The protocol would not address how several clients nego-
clients negotiate access; this is left to either a "social tiate access; this is left to either a "social protocol" or
protocol" or some other floor control mechanism. some other floor control mechanism.
1.5 Extending RTSP 1.5 Extending RTSP
Since not all media servers have the same functionality, media Since not all media servers have the same functionality, media
servers by necessity will support different sets of requests. For servers by necessity will support different sets of requests. For
example: example:
o A server may only be capable of playback thus has no need to + A server may only be capable of playback thus has no need to sup-
support the RECORD request. port the RECORD request.
o A server may not be capable of seeking (absolute positioning) + A server may not be capable of seeking (absolute positioning) if
if it is to support live events only. it is to support live events only.
o Some servers may not support setting stream parameters and + Some servers may not support setting stream parameters and thus
thus not support GET_PARAMETER and SET_PARAMETER. not support GET_PARAMETER and SET_PARAMETER.
A server SHOULD implement all header fields described in Section 12. A server SHOULD implement all header fields described in Section 12.
It is up to the creators of presentation descriptions not to ask the 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 [2], impossible of a server. This situation is similar in HTTP/1.1 [26],
where the methods described in [H19.6] are not likely to be supported where the methods described in [H19.5] are not likely to be supported
across all servers. across all servers.
RTSP can be extended in three ways, listed here in order of the RTSP can be extended in three ways, listed here in order of the mag-
magnitude of changes supported: nitude of changes supported:
o Existing methods can be extended with new parameters, as long + Existing methods can be extended with new parameters, as long as
as these parameters can be safely ignored by the recipient. these parameters can be safely ignored by the recipient. (This is
(This is equivalent to adding new parameters to an HTML tag.) equivalent to adding new parameters to an HTML tag.) If the
If the client needs negative acknowledgement when a method client needs negative acknowledgement when a method extension is
extension is not supported, a tag corresponding to the not supported, a tag corresponding to the extension may be added
extension may be added in the Require: field (see Section in the Require: field (see Section 12.32).
12.33).
o New methods can be added. If the recipient of the message does + New methods can be added. If the recipient of the message does
not understand the request, it responds with error code 501 not understand the request, it responds with error code 501 (Not
(Not Implemented) and the sender should not attempt to use Implemented) and the sender should not attempt to use this method
this method again. A client may also use the OPTIONS method again. A client may also use the OPTIONS method to inquire about
to inquire about methods supported by the server. The server methods supported by the server. The server SHOULD list the meth-
SHOULD list the methods it supports using the Public response ods it supports using the Public response header.
header.
o A new version of the protocol can be defined, allowing almost + A new version of the protocol can be defined, allowing almost all
all aspects (except the position of the protocol version aspects (except the position of the protocol version number) to
number) to change. change.
1.6 Overall Operation 1.6 Overall Operation
Each presentation and media stream may be identified by an RTSP URL. Each presentation and media stream may be identified by an RTSP URL.
The overall presentation and the properties of the media the The overall presentation and the properties of the media the presen-
presentation is made up of are defined by a presentation description tation is made up of are defined by a presentation description file,
file, the format of which is outside the scope of this specification. the format of which is outside the scope of this specification. The
The presentation description file may be obtained by the client using presentation description file may be obtained by the client using
HTTP or other means such as email and may not necessarily be stored HTTP or other means such as email and may not necessarily be stored
on the media server. on the media server.
For the purposes of this specification, a presentation description is For the purposes of this specification, a presentation description is
assumed to describe one or more presentations, each of which assumed to describe one or more presentations, each of which main-
maintains a common time axis. For simplicity of exposition and tains a common time axis. For simplicity of exposition and without
without loss of generality, it is assumed that the presentation loss of generality, it is assumed that the presentation description
description contains exactly one such presentation. A presentation contains exactly one such presentation. A presentation may contain
may contain several media streams. several media streams.
The presentation description file contains a description of the media The presentation description file contains a description of the media
streams making up the presentation, including their encodings, streams making up the presentation, including their encodings, lan-
language, and other parameters that enable the client to choose the guage, and other parameters that enable the client to choose the most
most appropriate combination of media. In this presentation appropriate combination of media. In this presentation description,
description, each media stream that is individually controllable by each media stream that is individually controllable by RTSP is iden-
RTSP is identified by an RTSP URL, which points to the media server tified by an RTSP URL, which points to the media server handling that
handling that particular media stream and names the stream stored on particular media stream and names the stream stored on that server.
that server. Several media streams can be located on different Several media streams can be located on different servers; for exam-
servers; for example, audio and video streams can be split across ple, audio and video streams can be split across servers for load
servers for load sharing. The description also enumerates which sharing. The description also enumerates which transport methods the
transport methods the server is capable of. server is capable of.
Besides the media parameters, the network destination address and Besides the media parameters, the network destination address and
port need to be determined. Several modes of operation can be port need to be determined. Several modes of operation can be distin-
distinguished: guished:
Unicast: The media is transmitted to the source of the RTSP Unicast: The media is transmitted to the source of the RTSP
request, with the port number chosen by the client. request, with the port number chosen by the client. Alterna-
Alternatively, the media is transmitted on the same tively, the media is transmitted on the same reliable stream
reliable stream as RTSP. as RTSP.
Multicast, server chooses address: The media server picks the Multicast, server chooses address: The media server picks the mul-
multicast address and port. This is the typical case for a ticast address and port. This is the typical case for a live
live or near-media-on-demand transmission. or near-media-on-demand transmission.
Multicast, client chooses address: If the server is to Multicast, client chooses address: If the server is to participate
participate in an existing multicast conference, the in an existing multicast conference, the multicast address,
multicast address, port and encryption key are given by the port and encryption key are given by the conference descrip-
conference description, established by means outside the tion, established by means outside the scope of this specifi-
scope of this specification. cation.
1.7 RTSP States 1.7 RTSP States
RTSP controls a stream which may be sent via a separate protocol, RTSP controls a stream which may be sent via a separate protocol,
independent of the control channel. For example, RTSP control may independent of the control channel. For example, RTSP control may
occur on a TCP connection while the data flows via UDP. Thus, data 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 delivery continues even if no RTSP requests are received by the media
server. Also, during its lifetime, a single media stream may be server. Also, during its lifetime, a single media stream may be con-
controlled by RTSP requests issued sequentially on different TCP trolled by RTSP requests issued sequentially on different TCP connec-
connections. Therefore, the server needs to maintain "session state" tions. Therefore, the server needs to maintain "session state" to be
to be able to correlate RTSP requests with a stream. The state able to correlate RTSP requests with a stream. The state transitions
transitions are described in Section A. are described in Section A.
Many methods in RTSP do not contribute to state. However, the Many methods in RTSP do not contribute to state. However, the follow-
following play a central role in defining the allocation and usage of ing play a central role in defining the allocation and usage of
stream resources on the server: SETUP, PLAY, RECORD, PAUSE, and stream resources on the server: SETUP, PLAY, RECORD, PAUSE, and TEAR-
TEARDOWN. DOWN.
SETUP: Causes the server to allocate resources for a stream and SETUP: Causes the server to allocate resources for a stream and
start an RTSP session. start an RTSP session.
PLAY and RECORD: Starts data transmission on a stream allocated PLAY and RECORD: Starts data transmission on a stream allocated via
via SETUP. SETUP.
PAUSE: Temporarily halts a stream without freeing server PAUSE: Temporarily halts a stream without freeing server resources.
resources.
TEARDOWN: Frees resources associated with the stream. The RTSP TEARDOWN: Frees resources associated with the stream. The RTSP
session ceases to exist on the server. session ceases to exist on the server.
RTSP methods that contribute to state use the Session RTSP methods that contribute to state use the Session header
header field (Section 12.38) to identify the RTSP session field (Section 12.37) to identify the RTSP session whose state
whose state is being manipulated. The server generates is being manipulated. The server generates session identifiers
session identifiers in response to SETUP requests (Section in response to SETUP requests (Section 10.4).
10.4).
1.8 Relationship with Other Protocols 1.8 Relationship with Other Protocols
RTSP has some overlap in functionality with HTTP. It also may RTSP has some overlap in functionality with HTTP. It also may inter-
interact with HTTP in that the initial contact with streaming content act with HTTP in that the initial contact with streaming content is
is often to be made through a web page. The current protocol often to be made through a web page. The current protocol specifica-
specification aims to allow different hand-off points between a web tion aims to allow different hand-off points between a web server and
server and the media server implementing RTSP. For example, the the media server implementing RTSP. For example, the presentation
presentation description can be retrieved using HTTP or RTSP, which description can be retrieved using HTTP or RTSP, which reduces
reduces roundtrips in web-browser-based scenarios, yet also allows roundtrips in web-browser-based scenarios, yet also allows for stan-
for standalone RTSP servers and clients which do not rely on HTTP at dalone RTSP servers and clients which do not rely on HTTP at all.
all.
However, RTSP differs fundamentally from HTTP in that data delivery However, RTSP differs fundamentally from HTTP in that data delivery
takes place out-of-band in a different protocol. HTTP is an takes place out-of-band in a different protocol. HTTP is an asymmet-
asymmetric protocol where the client issues requests and the server ric protocol where the client issues requests and the server
responds. In RTSP, both the media client and media server can issue responds. In RTSP, both the media client and media server can issue
requests. RTSP requests are also not stateless; they may set requests. RTSP requests are also not stateless; they may set parame-
parameters and continue to control a media stream long after the ters and continue to control a media stream long after the request
request has been acknowledged. has been acknowledged.
Re-using HTTP functionality has advantages in at least two Re-using HTTP functionality has advantages in at least two
areas, namely security and proxies. The requirements are areas, namely security and proxies. The requirements are very
very similar, so having the ability to adopt HTTP work on similar, so having the ability to adopt HTTP work on caches,
caches, proxies and authentication is valuable. proxies and authentication is valuable.
While most real-time media will use RTP as a transport protocol, RTSP While most real-time media will use RTP as a transport protocol, RTSP
is not tied to RTP. is not tied to RTP.
RTSP assumes the existence of a presentation description format that RTSP assumes the existence of a presentation description format that
can express both static and temporal properties of a presentation can express both static and temporal properties of a presentation
containing several media streams. containing several media streams.
2 Notational Conventions 2 Notational Conventions
Since many of the definitions and syntax are identical to HTTP/1.1, Since many of the definitions and syntax are identical to HTTP/1.1,
this specification only points to the section where they are defined 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 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 2068 [2]). 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 All the mechanisms specified in this document are described in both
prose and an augmented Backus-Naur form (BNF) similar to that used in prose and an augmented Backus-Naur form (BNF) similar to that used in
[H2.1]. It is described in detail in RFC 2234 [17], with the [H2.1]. It is described in detail in RFC 2234 [14], with the differ-
difference that this RTSP specification maintains the "1#" notation ence that this RTSP specification maintains the "1#" notation for
for comma-separated lists. comma-separated lists.
In this draft, we use indented and smaller-type paragraphs to provide In this draft, we use indented and smaller-type paragraphs to provide
background and motivation. This is intended to give readers who were background and motivation. This is intended to give readers who were
not involved with the formulation of the specification an not involved with the formulation of the specification an understand-
understanding of why things are the way that they are in RTSP. ing of why things are the way that they are in RTSP.
3 Protocol Parameters 3 Protocol Parameters
3.1 RTSP Version 3.1 RTSP Version
applies, with HTTP replaced by RTSP. HTTP Specification Section [H3.1] applies, with HTTP replaced by
RTSP.
3.2 RTSP URL 3.2 RTSP URL
The "rtsp" and "rtspu" schemes are used to refer to network resources The "rtsp" and "rtspu" schemes are used to refer to network resources
via the RTSP protocol. This section defines the scheme-specific via the RTSP protocol. This section defines the scheme-specific syn-
syntax and semantics for RTSP URLs. tax and semantics for RTSP URLs.
rtsp_URL _ ( "rtsp:" | "rtspu:" ) rtsp_URL = ( "rtsp:" | "rtspu:" )
"//" host [ ":" port ] [ abs_path ] "//" host [ ":" port ] [ abs_path ]
host _ <A legal Internet host domain name of IP address host = <A legal Internet host domain name of IP address
(in dotted decimal form), as defined by Section 2.1 (in dotted decimal form), as defined by Section 2.1
of RFC 1123 [18]> of RFC 1123 [15]>
port _ *DIGIT port = *DIGIT
abs_path is defined in [H3.2.1]. abs_path is defined in [H3.2.1].
Note that fragment and query identifiers do not have a Note that fragment and query identifiers do not have a well-
well-defined meaning at this time, with the interpretation defined meaning at this time, with the interpretation left to
left to the RTSP server. the RTSP server.
The scheme rtsp requires that commands are issued via a reliable The scheme rtsp requires that commands are issued via a reliable pro-
protocol (within the Internet, TCP), while the scheme rtspu tocol (within the Internet, TCP), while the scheme rtspu identifies
identifies an unreliable protocol (within the Internet, UDP). an unreliable protocol (within the Internet, UDP).
If the port is empty or not given, port 554 is assumed. The If the port is empty or not given, port 554 is assumed. The semantics
semantics are that the identified resource can be controlled by RTSP are that the identified resource can be controlled by RTSP at the
at the server listening for TCP (scheme "rtsp") connections or UDP server listening for TCP (scheme "rtsp") connections or UDP (scheme
(scheme "rtspu") packets on that port of host, and the Request-URI "rtspu") packets on that port of host, and the Request-URI for the
for the resource is rtsp_URL. resource is rtsp_URL.
The use of IP addresses in URLs SHOULD be avoided whenever possible The use of IP addresses in URLs SHOULD be avoided whenever possible
(see RFC 1924 [19]). (see RFC 1924 [16]).
A presentation or a stream is identified by a textual media A presentation or a stream is identified by a textual media identi-
identifier, using the character set and escape conventions [H3.2] of fier, using the character set and escape conventions [H3.2] of URLs
URLs (RFC 1738 [20]). URLs may refer to a stream or an aggregate of (RFC 1738 [17]). URLs may refer to a stream or an aggregate of
streams, i.e., a presentation. Accordingly, requests described in streams, i.e., a presentation. Accordingly, requests described in
Section 10 can apply to either the whole presentation or an Section 10 can apply to either the whole presentation or an individ-
individual stream within the presentation. Note that some request ual stream within the presentation. Note that some request methods
methods can only be applied to streams, not presentations and vice can only be applied to streams, not presentations and vice versa.
versa.
For example, the RTSP URL: For example, the RTSP URL:
rtsp://media.example.com:554/twister/audiotrack rtsp://media.example.com:554/twister/audiotrack
identifies the audio stream within the presentation "twister", which identifies the audio stream within the presentation "twister", which can
can be controlled via RTSP requests issued over a TCP connection to be controlled via RTSP requests issued over a TCP connection to port 554
port 554 of host media.example.com of host media.example.com
Also, the RTSP URL: Also, the RTSP URL:
rtsp://media.example.com:554/twister rtsp://media.example.com:554/twister
identifies the presentation "twister", which may be composed of audio identifies the presentation "twister", which may be composed of audio
and video streams. and video streams.
This does not imply a standard way to reference streams in This does not imply a standard way to reference streams in
URLs. The presentation description defines the hierarchical URLs. The presentation description defines the hierarchical
relationships in the presentation and the URLs for the relationships in the presentation and the URLs for the indi-
individual streams. A presentation description may name a vidual streams. A presentation description may name a stream
stream "a.mov" and the whole presentation "b.mov". "a.mov" and the whole presentation "b.mov".
The path components of the RTSP URL are opaque to the client and do The path components of the RTSP URL are opaque to the client and do
not imply any particular file system structure for the server. not imply any particular file system structure for the server.
This decoupling also allows presentation descriptions to be This decoupling also allows presentation descriptions to be
used with non-RTSP media control protocols simply by used with non-RTSP media control protocols simply by replacing
replacing the scheme in the URL. the scheme in the URL.
3.3 Conference Identifiers
Conference identifiers are opaque to RTSP and are encoded using
standard URI encoding methods (i.e., LWS is escaped with %). They can
contain any octet value. The conference identifier MUST be globally
unique. For H.323, the conferenceID value is to be used.
conference-id _ 1*xchar
Conference identifiers are used to allow RTSP sessions to
obtain parameters from multimedia conferences the media
server is participating in. These conferences are created
by protocols outside the scope of this specification, e.g.,
H.323 [13] or SIP [12]. Instead of the RTSP client
explicitly providing transport information, for example, it
asks the media server to use the values in the conference
description instead.
3.4 Session Identifiers 3.3 Session Identifiers
Session identifiers are opaque strings of arbitrary length. Linear Session identifiers are opaque strings of arbitrary length. Linear
white space must be URL-escaped. A session identifier MUST be chosen 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 randomly and MUST be at least eight octets long to make guessing it
more difficult. (See Section 16.) more difficult. (See Section 16.)
session-id = 8*( ALPHA | DIGIT | safe )
session-id _ 8*( ALPHA | DIGIT | safe ) 3.4 SMPTE Relative Timestamps
3.5 SMPTE Relative Timestamps
A SMPTE relative timestamp expresses time relative to the start of A SMPTE relative timestamp expresses time relative to the start of
the clip. Relative timestamps are expressed as SMPTE time codes for the clip. Relative timestamps are expressed as SMPTE time codes for
frame-level access accuracy. The time code has the format frame-level access accuracy. The time code has the format
hours:minutes:seconds:frames.subframes hours:minutes:seconds:frames.subframes,
,
with the origin at the start of the clip. The default smpte format 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. 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 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 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 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 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 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 minute. If the frame value is zero, it may be omitted. Subframes are
measured in one-hundredth of a frame. measured in one-hundredth of a frame.
smpte-range _ smpte-type "=" smpte-range-spec smpte-range = smpte-type "=" smpte-range-spec
smpte-range-spec _ ( smpte-time "-" [ smpte-time ] ) | ( "-" smpte-time ) smpte-range-spec = ( smpte-time "-" [ smpte-time ] ) | ( "-" smpte-time )
smpte-type _ "smpte" | "smpte-30-drop" | "smpte-25" smpte-type = "smpte" | "smpte-30-drop" | "smpte-25"
; other timecodes may be added ; other timecodes may be added
smpte-time _ 1*2DIGIT ":" 1*2DIGIT ":" 1*2DIGIT smpte-time = 1*2DIGIT ":" 1*2DIGIT ":" 1*2DIGIT
[ ":" 1*2DIGIT ] [ "." 1*2DIGIT ] [ ":" 1*2DIGIT ] [ "." 1*2DIGIT ]
Examples: Examples:
smpte=10:12:33:20- smpte=10:12:33:20-
smpte=10:07:33- smpte=10:07:33-
smpte=10:07:00-10:07:33:05.01 smpte=10:07:00-10:07:33:05.01
smpte-25=10:07:00-10:07:33:05.01 smpte-25=10:07:00-10:07:33:05.01
3.6 Normal Play Time 3.5 Normal Play Time
Normal play time (NPT) indicates the stream absolute position Normal play time (NPT) indicates the stream absolute position rela-
relative to the beginning of the presentation. The timestamp consists tive to the beginning of the presentation. The timestamp consists of
of a decimal fraction. The part left of the decimal may be expressed a decimal fraction. The part left of the decimal may be expressed in
in either seconds or hours, minutes, and seconds. The part right of either seconds or hours, minutes, and seconds. The part right of the
the decimal point measures fractions of a second. decimal point measures fractions of a second.
The beginning of a presentation corresponds to 0.0 seconds. Negative The beginning of a presentation corresponds to 0.0 seconds. Negative
values are not defined. The special constant now is defined as the values are not defined. The special constant now is defined as the
current instant of a live event. It may be used only for live events. current instant of a live event. It may be used only for live events.
NPT is defined as in DSM-CC: "Intuitively, NPT is the clock the NPT is defined as in DSM-CC: "Intuitively, NPT is the clock the
viewer associates with a program. It is often digitally displayed on viewer associates with a program. It is often digitally displayed on
a VCR. NPT advances normally when in normal play mode (scale = 1), a VCR. NPT advances normally when in normal play mode (scale = 1),
advances at a faster rate when in fast scan forward (high positive advances at a faster rate when in fast scan forward (high positive
scale ratio), decrements when in scan reverse (high negative scale scale ratio), decrements when in scan reverse (high negative scale
ratio) and is fixed in pause mode. NPT is (logically) equivalent to ratio) and is fixed in pause mode. NPT is (logically) equivalent to
SMPTE time codes." [5] SMPTE time codes." [5]
npt-range _ ["npt" "="] npt-range-spec npt-range = ["npt" "="] npt-range-spec
; implementations SHOULD use npt= prefix, but SHOULD ; implementations SHOULD use npt= prefix, but SHOULD
; be prepared to interoperate with RFC 2326 ; be prepared to interoperate with RFC 2326
; implementations which don't use it ; implementations which don't use it
npt-range-spec _ ( npt-time "-" [ npt-time ] ) | ( "-" npt-time ) npt-range-spec = ( npt-time "-" [ npt-time ] ) | ( "-" npt-time )
npt-time _ "now" | npt-sec | npt-hhmmss npt-time = "now" | npt-sec | npt-hhmmss
npt-sec _ 1*DIGIT [ "." *DIGIT ] npt-sec = 1*DIGIT [ "." *DIGIT ]
npt-hhmmss _ npt-hh ":" npt-mm ":" npt-ss [ "." *DIGIT ] npt-hhmmss = npt-hh ":" npt-mm ":" npt-ss [ "." *DIGIT ]
npt-hh _ 1*DIGIT ; any positive number npt-hh = 1*DIGIT ; any positive number
npt-mm _ 1*2DIGIT ; 0-59 npt-mm = 1*2DIGIT ; 0-59
npt-ss _ 1*2DIGIT ; 0-59 npt-ss = 1*2DIGIT ; 0-59
Examples: Examples:
npt=123.45-125 npt=123.45-125
npt=12:05:35.3- npt=12:05:35.3-
npt=now- npt=now-
The syntax conforms to ISO 8601. The npt-sec notation is The syntax conforms to ISO 8601. The npt-sec notation is opti-
optimized for automatic generation, the ntp-hhmmss notation mized for automatic generation, the ntp-hhmmss notation for
for consumption by human readers. The "now" constant allows consumption by human readers. The "now" constant allows
clients to request to receive the live feed rather than the clients to request to receive the live feed rather than the
stored or time-delayed version. This is needed since stored or time-delayed version. This is needed since neither
neither absolute time nor zero time are appropriate for absolute time nor zero time are appropriate for this case.
this case.
3.7 Absolute Time 3.6 Absolute Time
Absolute time is expressed as ISO 8601 timestamps, using UTC (GMT). Absolute time is expressed as ISO 8601 timestamps, using UTC (GMT).
Fractions of a second may be indicated. Fractions of a second may be indicated.
utc-range _ "clock" "=" utc-time "-" [ utc-time ] utc-range = ["clock" "="] utc-range-spec
utc-time _ utc-date "T" utc-time "Z" utc-range-spec = ( utc-time "-" [ utc-time ] ) | ( "-" utc-time )
utc-date _ 8DIGIT ; < YYYYMMDD > utc-time = utc-date "T" utc-time "Z"
utc-time _ 6DIGIT [ "." fraction ] ; < HHMMSS.fraction > utc-date = 8DIGIT ; < YYYYMMDD >
utc-time = 6DIGIT [ "." fraction ] ; < HHMMSS.fraction >
Example for November 8, 1996 at 14h37 and 20 and a quarter seconds Example for November 8, 1996 at 14h37 and 20 and a quarter seconds
UTC: UTC:
19961108T143720.25Z 19961108T143720.25Z
3.8 Option Tags 3.7 Option Tags
Option tags are unique identifiers used to designate new options in Option tags are unique identifiers used to designate new options in
RTSP. These tags are used in in Require (Section 12.33) and Proxy- RTSP. These tags are used in in Require (Section 12.32) and Proxy-
Require (Section 12.28) header fields. Require (Section 12.27) header fields.
Syntax: Syntax:
option-tag _ token option-tag = token
The creator of a new RTSP option should either prefix the option with 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 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 for a feature whose inventor can be reached at "foo.com"), or regis-
register the new option with the Internet Assigned Numbers Authority ter the new option with the Internet Assigned Numbers Authority
(IANA). (IANA).
3.8.1 Registering New Option Tags with IANA 3.7.1 Registering New Option Tags with IANA
When registering a new RTSP option, the following information should When registering a new RTSP option, the following information should
be provided: be provided:
o Name and description of option. The name may be of any length, + Name and description of option. The name may be of any length,
but SHOULD be no more than twenty characters long. The name but SHOULD be no more than twenty characters long. The name MUST
MUST not contain any spaces, control characters or periods. not contain any spaces, control characters or periods.
o Indication of who has change control over the option (for + Indication of who has change control over the option (for exam-
example, IETF, ISO, ITU-T, other international standardization ple, IETF, ISO, ITU-T, other international standardization bod-
bodies, a consortium or a particular company or group of ies, a consortium or a particular company or group of companies);
companies);
o A reference to a further description, if available, for + A reference to a further description, if available, for example
example (in order of preference) an RFC, a published paper, a (in order of preference) an RFC, a published paper, a patent fil-
patent filing, a technical report, documented source code or a ing, a technical report, documented source code or a computer
computer manual; manual;
o For proprietary options, contact information (postal and email + For proprietary options, contact information (postal and email
address); address);
4 RTSP Message 4 RTSP Message
RTSP is a text-based protocol and uses the ISO 10646 character set in RTSP is a text-based protocol and uses the ISO 10646 character set in
UTF-8 encoding (RFC 2279 [22]). Lines are terminated by CRLF, but UTF-8 encoding (RFC 2279 [18]). Lines are terminated by CRLF, but
receivers should be prepared to also interpret CR and LF by receivers should be prepared to also interpret CR and LF by them-
themselves as line terminators. selves as line terminators.
Text-based protocols make it easier to add optional Text-based protocols make it easier to add optional parameters
parameters in a self-describing manner. Since the number of in a self-describing manner. Since the number of parameters
parameters and the frequency of commands is low, processing and the frequency of commands is low, processing efficiency is
efficiency is not a concern. Text-based protocols, if done not a concern. Text-based protocols, if done carefully, also
carefully, also allow easy implementation of research allow easy implementation of research prototypes in scripting
prototypes in scripting languages such as Tcl, Visual Basic languages such as Tcl, Visual Basic and Perl.
and Perl.
The 10646 character set avoids tricky character set switching, but is The 10646 character set avoids tricky character set switching, but is
invisible to the application as long as US-ASCII is being used. This 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 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 into Unicode with a high-order octet of zero. ISO 8859-1 characters
with the most-significant bit set are represented as 1100001x with the most-significant bit set are represented as 1100001x
10xxxxxx. (See RFC 2279 [22]) 10xxxxxx. (See RFC 2279 [18])
RTSP messages can be carried over any lower-layer transport protocol RTSP messages can be carried over any lower-layer transport protocol
that is 8-bit clean. that is 8-bit clean.
Requests contain methods, the object the method is operating upon and Requests contain methods, the object the method is operating upon and
parameters to further describe the method. Methods are idempotent, parameters to further describe the method. Methods are idempotent,
unless otherwise noted. Methods are also designed to require little unless otherwise noted. Methods are also designed to require little
or no state maintenance at the media server. or no state maintenance at the media server.
4.1 Message Types 4.1 Message Types
skipping to change at page 1, line 788 skipping to change at page 1, line 749
4.3 Message Body 4.3 Message Body
See [H4.3] See [H4.3]
4.4 Message Length 4.4 Message Length
When a message body is included with a message, the length of that 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): body is determined by one of the following (in order of precedence):
1. Any response message which MUST NOT include a message body 1. Any response message which MUST NOT include a message body
(such as the 1xx, 204, and 304 responses) is always (such as the 1xx, 204, and 304 responses) is always terminated
terminated by the first empty line after the header fields, by the first empty line after the header fields, regardless of
regardless of the entity-header fields present in the the entity-header fields present in the message. (Note: An
message. (Note: An empty line consists of only CRLF.) empty line consists of only CRLF.)
2. If a Content-Length header field (section 12.15) is
present, its value in bytes represents the length of the 2. If a Content-Length header field (section 12.14) is present,
message-body. If this header field is not present, a value its value in bytes represents the length of the message-body.
of zero is assumed. 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" Note that RTSP does not (at present) support the HTTP/1.1 "chunked"
transfer coding(see [H3.6]) and requires the presence of the transfer coding(see [H3.6.1]) and requires the presence of the Con-
Content-Length header field. tent-Length header field.
Given the moderate length of presentation descriptions Given the moderate length of presentation descriptions
returned, the server should always be able to determine its returned, the server should always be able to determine its
length, even if it is generated dynamically, making the length, even if it is generated dynamically, making the chun-
chunked transfer encoding unnecessary. ked transfer encoding unnecessary.
5 General Header Fields 5 General Header Fields
See [H4.5], except that Pragma, Transfer-Encoding and Upgrade See [H4.5], except that Pragma, Trailer, Transfer-Encoding, Upgrade,
headers are not defined: and Warning headers are not defined:
general-header = Cache-Control ; Section 12.9 general-header = Cache-Control ; Section 12.9
| Connection ; Section 12.11 | Connection ; Section 12.10
| CSeq ; Section 12.18 | CSeq ; Section 12.17
| Date ; Section 12.19 | Date ; Section 12.18
| Via ; Section 12.44 | Via ; Section 12.44
6 Request 6 Request
A request message from a client to a server or vice versa includes, 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 within the first line of that message, the method to be applied to
the resource, the identifier of the resource, and the protocol the resource, the identifier of the resource, and the protocol ver-
version in use. sion in use.
Request = Request-Line ; Section 6.1 Request = Request-Line ; Section 6.1
*( general-header ; Section 5 *( general-header ; Section 5
| request-header ; Section 6.2 | request-header ; Section 6.2
| entity-header ) ; Section 8.1 | entity-header ) ; Section 8.1
CRLF CRLF
[ message-body ] ; Section 4.3 [ message-body ] ; Section 4.3
6.1 Request Line 6.1 Request Line
Request-Line _ Method SP Request-URI SP RTSP-Version CRLF Request-Line = Method SP Request-URI SP RTSP-Version CRLF
Method = "DESCRIBE" ; Section 10.2 Method = "DESCRIBE" ; Section 10.2
| "ANNOUNCE" ; Section 10.3 | "ANNOUNCE" ; Section 10.3
| "GET_PARAMETER" ; Section 10.8 | "GET_PARAMETER" ; Section 10.8
| "OPTIONS" ; Section 10.1 | "OPTIONS" ; Section 10.1
| "PAUSE" ; Section 10.6 | "PAUSE" ; Section 10.6
| "PLAY" ; Section 10.5 | "PLAY" ; Section 10.5
| "RECORD" ; Section 10.11 | "RECORD" ; Section 10.11
| "REDIRECT" ; Section 10.10 | "REDIRECT" ; Section 10.10
| "SETUP" ; Section 10.4 | "SETUP" ; Section 10.4
| "SET_PARAMETER" ; Section 10.9 | "SET_PARAMETER" ; Section 10.9
| "TEARDOWN" ; Section 10.7 | "TEARDOWN" ; Section 10.7
| extension-method | extension-method
extension-method _ token extension-method = token
Request-URI _ "*" | absolute_URI Request-URI = "*" | absolute_URI
RTSP-Version _ "RTSP" "/" 1*DIGIT "." 1*DIGIT RTSP-Version = "RTSP" "/" 1*DIGIT "." 1*DIGIT
6.2 Request Header Fields 6.2 Request Header Fields
request-header = Accept ; Section 12.1 request-header = Accept ; Section 12.1
| Accept-Encoding ; Section 12.2 | Accept-Encoding ; Section 12.2
| Accept-Language ; Section 12.3 | Accept-Language ; Section 12.3
| Authorization ; Section 12.6 | Authorization ; Section 12.6
| Bandwidth ; Section 12.7 | Bandwidth ; Section 12.7
| Blocksize ; Section 12.8 | Blocksize ; Section 12.8
| Conference ; Section 12.10 | From ; Section 12.20
| From ; Section 12.21 | If-Modified-Since ; Section 12.23
| If-Modified-Since ; Section 12.24 | Proxy-Require ; Section 12.27
| Proxy-Require ; Section 12.28 | Range ; Section 12.29
| Range ; Section 12.30 | Referer ; Section 12.30
| Referer ; Section 12.31 | Require ; Section 12.32
| Require ; Section 12.33 | Scale ; Section 12.34
| Scale ; Section 12.35 | Session ; Section 12.37
| Session ; Section 12.38 | Speed ; Section 12.35
| Speed ; Section 12.36
| Transport ; Section 12.40 | Transport ; Section 12.40
| User-Agent ; Section 12.42 | User-Agent ; Section 12.42
Note that in contrast to HTTP/1.1 [2], RTSP requests always contain Note that in contrast to HTTP/1.1 [26], RTSP requests always contain
the absolute URL (that is, including the scheme, host and port) the absolute URL (that is, including the scheme, host and port)
rather than just the absolute path. rather than just the absolute path.
HTTP/1.1 requires servers to understand the absolute URL, HTTP/1.1 requires servers to understand the absolute URL, but
but clients are supposed to use the Host request header. clients are supposed to use the Host request header. This is
This is purely needed for backward-compatibility with purely needed for backward-compatibility with HTTP/1.0
HTTP/1.0 servers, a consideration that does not apply to servers, a consideration that does not apply to RTSP.
RTSP.
The asterisk "*" in the Request-URI means that the request does not The asterisk "*" in the Request-URI means that the request does not
apply to a particular resource, but to the server itself, and is only apply to a particular resource, but to the server itself, and is only
allowed when the method used does not necessarily apply to a allowed when the method used does not necessarily apply to a
resource. One example would be: resource. One example would be:
OPTIONS * RTSP/1.0 OPTIONS * RTSP/1.0
7 Response 7 Response
skipping to change at page 1, line 914 skipping to change at page 1, line 875
[ message-body ] ; Section 4.3 [ message-body ] ; Section 4.3
7.1 Status-Line 7.1 Status-Line
The first line of a Response message is the Status-Line, consisting The first line of a Response message is the Status-Line, consisting
of the protocol version followed by a numeric status code, and the of the protocol version followed by a numeric status code, and the
textual phrase associated with the status code, with each element textual phrase associated with the status code, with each element
separated by SP characters. No CR or LF is allowed except in the separated by SP characters. No CR or LF is allowed except in the
final CRLF sequence. final CRLF sequence.
Status-Line _ RTSP-Version SP Status-Code SP Reason-Phrase CRLF Status-Line = RTSP-Version SP Status-Code SP Reason-Phrase CRLF
7.1.1 Status Code and Reason Phrase 7.1.1 Status Code and Reason Phrase
The Status-Code element is a 3-digit integer result code of the The Status-Code element is a 3-digit integer result code of the
attempt to understand and satisfy the request. These codes are fully attempt to understand and satisfy the request. These codes are fully
defined in Section 11. The Reason-Phrase is intended to give a short defined in Section 11. The Reason-Phrase is intended to give a short
textual description of the Status-Code. The Status-Code is intended textual description of the Status-Code. The Status-Code is intended
for use by automata and the Reason-Phrase is intended for the human 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- user. The client is not required to examine or display the Reason-
Phrase. Phrase.
The first digit of the Status-Code defines the class of response. The first digit of the Status-Code defines the class of response. The
The last two digits do not have any categorization role. There are 5 last two digits do not have any categorization role. There are 5
values for the first digit: values for the first digit:
o 1xx: Informational - Request received, continuing process + 1xx: Informational - Request received, continuing process
o 2xx: Success - The action was successfully received, + 2xx: Success - The action was successfully received, understood,
understood, and accepted and accepted
o 3xx: Redirection - Further action must be taken in order to + 3xx: Redirection - Further action must be taken in order to com-
complete the request plete the request
o 4xx: Client Error - The request contains bad syntax or cannot + 4xx: Client Error - The request contains bad syntax or cannot be
be fulfilled fulfilled
o 5xx: Server Error - The server failed to fulfill an apparently + 5xx: Server Error - The server failed to fulfill an apparently
valid request valid request
The individual values of the numeric status codes defined for The individual values of the numeric status codes defined for
RTSP/1.0, and an example set of corresponding Reason-Phrase's, are RTSP/1.0, and an example set of corresponding Reason-Phrase's, are
presented below. The reason phrases listed here are only recommended presented below. The reason phrases listed here are only recommended
-- they may be replaced by local equivalents without affecting the -- they may be replaced by local equivalents without affecting the
protocol. Note that RTSP adopts most HTTP/1.1 [2] status codes and protocol. Note that RTSP adopts most HTTP/1.1 [26] status codes and
adds RTSP-specific status codes starting at x50 to avoid conflicts adds RTSP-specific status codes starting at x50 to avoid conflicts
with newly defined HTTP status codes. with newly defined HTTP status codes.
Status-Code = "100" ; Continue Status-Code = "100" ; Continue
| "200" ; OK | "200" ; OK
| "201" ; Created | "201" ; Created
| "250" ; Low on Storage Space | "250" ; Low on Storage Space
| "300" ; Multiple Choices | "300" ; Multiple Choices
| "301" ; Moved Permanently | "301" ; Moved Permanently
| "302" ; Moved Temporarily | "302" ; Moved Temporarily
skipping to change at page 1, line 977 skipping to change at page 1, line 939
| "406" ; Not Acceptable | "406" ; Not Acceptable
| "407" ; Proxy Authentication Required | "407" ; Proxy Authentication Required
| "408" ; Request Time-out | "408" ; Request Time-out
| "410" ; Gone | "410" ; Gone
| "411" ; Length Required | "411" ; Length Required
| "412" ; Precondition Failed | "412" ; Precondition Failed
| "413" ; Request Entity Too Large | "413" ; Request Entity Too Large
| "414" ; Request-URI Too Large | "414" ; Request-URI Too Large
| "415" ; Unsupported Media Type | "415" ; Unsupported Media Type
| "451" ; Parameter Not Understood | "451" ; Parameter Not Understood
| "452" ; Conference Not Found | "452" ; reserved
| "453" ; Not Enough Bandwidth | "453" ; Not Enough Bandwidth
| "454" ; Session Not Found | "454" ; Session Not Found
| "455" ; Method Not Valid in This State | "455" ; Method Not Valid in This State
| "456" ; Header Field Not Valid for Resource | "456" ; Header Field Not Valid for Resource
| "457" ; Invalid Range | "457" ; Invalid Range
| "458" ; Parameter Is Read-Only | "458" ; Parameter Is Read-Only
| "459" ; Aggregate operation not allowed | "459" ; Aggregate operation not allowed
| "460" ; Only aggregate operation allowed | "460" ; Only aggregate operation allowed
| "461" ; Unsupported transport | "461" ; Unsupported transport
| "462" ; Destination unreachable | "462" ; Destination unreachable
skipping to change at page 1, line 996 skipping to change at page 1, line 958
| "461" ; Unsupported transport | "461" ; Unsupported transport
| "462" ; Destination unreachable | "462" ; Destination unreachable
| "500" ; Internal Server Error | "500" ; Internal Server Error
| "501" ; Not Implemented | "501" ; Not Implemented
| "502" ; Bad Gateway | "502" ; Bad Gateway
| "503" ; Service Unavailable | "503" ; Service Unavailable
| "504" ; Gateway Time-out | "504" ; Gateway Time-out
| "505" ; RTSP Version not supported | "505" ; RTSP Version not supported
| "551" ; Option not supported | "551" ; Option not supported
| extension-code | extension-code
extension-code = 3DIGIT extension-code = 3DIGIT
Reason-Phrase = *<TEXT, excluding CR, LF> Reason-Phrase = *<TEXT, excluding CR, LF>
RTSP status codes are extensible. RTSP applications are not required RTSP status codes are extensible. RTSP applications are not required
to understand the meaning of all registered status codes, though such to understand the meaning of all registered status codes, though such
understanding is obviously desirable. However, applications MUST understanding is obviously desirable. However, applications MUST
understand the class of any status code, as indicated by the first understand the class of any status code, as indicated by the first
digit, and treat any unrecognized response as being equivalent to the digit, and treat any unrecognized response as being equivalent to the
x00 status code of that class, with the exception that an x00 status code of that class, with the exception that an unrecog-
unrecognized response MUST NOT be cached. For example, if an nized response MUST NOT be cached. For example, if an unrecognized
unrecognized status code of 431 is received by the client, it can status code of 431 is received by the client, it can safely assume
safely assume that there was something wrong with its request and that there was something wrong with its request and treat the
treat the response as if it had received a 400 status code. In such response as if it had received a 400 status code. In such cases, user
cases, user agents SHOULD present to the user the entity returned agents SHOULD present to the user the entity returned with the
with the response, since that entity is likely to include human- response, since that entity is likely to include human-readable
readable information which will explain the unusual status. information which will explain the unusual status.
7.1.2 Response Header Fields 7.1.2 Response Header Fields
The response-header fields allow the request recipient to pass The response-header fields allow the request recipient to pass addi-
additional information about the response which cannot be placed in tional information about the response which cannot be placed in the
the Status-Line. These header fields give information about the Status-Line. These header fields give information about the server
server and about further access to the resource identified by the and about further access to the resource identified by the Request-
Request-URI. URI.
response-header = Location ; Section 12.26 response-header = Location ; Section 12.25
| Proxy-Authenticate ; Section 12.27 | Proxy-Authenticate ; Section 12.26
| Public ; Section 12.29 | Public ; Section 12.28
| Range ; Section 12.30 | Range ; Section 12.29
| Retry-After ; Section 12.32 | Retry-After ; Section 12.31
| RTP-Info ; Section 12.34 | RTP-Info ; Section 12.33
| Scale ; Section 12.35 | Scale ; Section 12.34
| Session ; Section 12.38 | Session ; Section 12.37
| Server ; Section 12.37 | Server ; Section 12.36
| Speed ; Section 12.36 | Speed ; Section 12.35
| Transport ; Section 12.40 | Transport ; Section 12.40
| Unsupported ; Section 12.41 | Unsupported ; Section 12.41
| Vary ; Section 12.43 | Vary ; Section 12.43
| WWW-Authenticate ; Section 12.45 | WWW-Authenticate ; Section 12.45
Response-header field names can be extended reliably only in Response-header field names can be extended reliably only in combina-
combination with a change in the protocol version. However, new or tion with a change in the protocol version. However, new or experi-
experimental header fields MAY be given the semantics of response- mental header fields MAY be given the semantics of response-header
header fields if all parties in the communication recognize them to fields if all parties in the communication recognize them to be
be response-header fields. Unrecognized header fields are treated as response-header fields. Unrecognized header fields are treated as
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 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 12.12
| Content-Encoding ; Section 12.13
| Content-Language ; Section 12.14
| Content-Length ; Section 12.15
| Content-Location ; Section 12.16
| Content-Type ; Section 12.17
| Expires ; Section 12.20
| Last-Modified ; Section 12.25
| 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]
9 Connections
RTSP requests can be transmitted in several different ways:
o persistent transport connections used for several request-
response transactions;
o one connection per request/response transaction;
o 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
connections, as the media server otherwise has no reliable way of
Code reason Code reason
_______________________________________________________ --------------------------------------------------------
100 Continue all 100 Continue all
--------------------------------------------------------
_______________________________________________________
200 OK all 200 OK all
201 Created RECORD 201 Created RECORD
250 Low on Storage Space RECORD 250 Low on Storage Space RECORD
_______________________________________________________ --------------------------------------------------------
300 Multiple Choices all 300 Multiple Choices all
301 Moved Permanently all 301 Moved Permanently all
302 Moved Temporarily all 302 Moved Temporarily all
303 See Other all 303 See Other all
305 Use Proxy all 305 Use Proxy all
--------------------------------------------------------
_______________________________________________________
400 Bad Request all 400 Bad Request all
401 Unauthorized all 401 Unauthorized all
402 Payment Required all 402 Payment Required all
403 Forbidden all 403 Forbidden all
404 Not Found all 404 Not Found all
405 Method Not Allowed all 405 Method Not Allowed all
406 Not Acceptable all 406 Not Acceptable all
407 Proxy Authentication Required all 407 Proxy Authentication Required all
408 Request Timeout all 408 Request Timeout all
410 Gone all 410 Gone all
411 Length Required all 411 Length Required all
412 Precondition Failed DESCRIBE, SETUP 412 Precondition Failed DESCRIBE, SETUP
413 Request Entity Too Large all 413 Request Entity Too Large all
414 Request-URI Too Long all 414 Request-URI Too Long all
415 Unsupported Media Type all 415 Unsupported Media Type all
451 Parameter Not Understood SETUP 451 Parameter Not Understood SETUP
452 Illegal Conference Identifier SETUP 452 reserved n/a
453 Not Enough Bandwidth SETUP 453 Not Enough Bandwidth SETUP
454 Session Not Found all 454 Session Not Found all
455 Method Not Valid In This State all 455 Method Not Valid In This State all
456 Header Field Not Valid all 456 Header Field Not Valid all
457 Invalid Range PLAY 457 Invalid Range PLAY
458 Parameter Is Read-Only SET_PARAMETER 458 Parameter Is Read-Only SET_PARAMETER
459 Aggregate Operation Not Allowed all 459 Aggregate Operation Not Allowed all
460 Only Aggregate Operation Allowed all 460 Only Aggregate Operation Allowed all
461 Unsupported Transport all 461 Unsupported Transport all
462 Destination Unreachable all 462 Destination Unreachable all
_______________________________________________________ --------------------------------------------------------
500 Internal Server Error all 500 Internal Server Error all
501 Not Implemented all 501 Not Implemented all
502 Bad Gateway all 502 Bad Gateway all
503 Service Unavailable all 503 Service Unavailable all
504 Gateway Timeout all 504 Gateway Timeout all
505 RTSP Version Not Supported all 505 RTSP Version Not Supported all
551 Option not support all 551 Option not support all
Table 1: Status codes and their usage with RTSP methods Table 1: Status codes and their usage with RTSP methods
reaching the client. Also, this is the only way that requests from
media server to client are likely to traverse firewalls. 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 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]
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 9.1 Pipelining
A client that supports persistent connections or connectionless mode A client that supports persistent connections or connectionless mode
MAY "pipeline" its requests (i.e., send multiple requests without MAY "pipeline" its requests (i.e., send multiple requests without
waiting for each response). A server MUST send its responses to those waiting for each response). A server MUST send its responses to those
requests in the same order that the requests were received. requests in the same order that the requests were received.
9.2 Reliability and Acknowledgements 9.2 Reliability and Acknowledgements
Requests are acknowledged by the receiver unless they are sent to a Requests are acknowledged by the receiver unless they are sent to a
multicast group. If there is no acknowledgement, the sender may multicast group. If there is no acknowledgement, the sender may
resend the same message after a timeout of one round-trip time (RTT). resend the same message after a timeout of one round-trip time (RTT).
The round-trip time is estimated as in TCP (RFC 1123) [18], with an 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 initial round-trip value of 500 ms. An implementation MAY cache the
last RTT measurement as the initial value for future connections. last RTT measurement as the initial value for future connections.
If a reliable transport protocol is used to carry RTSP, requests MUST If a reliable transport protocol is used to carry RTSP, requests MUST
NOT be retransmitted; the RTSP application MUST instead rely on the NOT be retransmitted; the RTSP application MUST instead rely on the
underlying transport to provide reliability. underlying transport to provide reliability.
If both the underlying reliable transport such as TCP and If both the underlying reliable transport such as TCP and the
the RTSP application retransmit requests, it is possible RTSP application retransmit requests, it is possible that each
that each packet loss results in two retransmissions. The packet loss results in two retransmissions. The receiver can-
receiver cannot typically take advantage of the not typically take advantage of the application-layer retrans-
application-layer retransmission since the transport stack mission since the transport stack will not deliver the
will not deliver the application-layer retransmission application-layer retransmission before the first attempt has
before the first attempt has reached the receiver. If the reached the receiver. If the packet loss is caused by conges-
packet loss is caused by congestion, multiple tion, multiple retransmissions at different layers will exac-
retransmissions at different layers will exacerbate the erbate the congestion.
congestion.
If RTSP is used over a small-RTT LAN, standard procedures for If RTSP is used over a small-RTT LAN, standard procedures for opti-
optimizing initial TCP round trip estimates, such as those used in mizing initial TCP round trip estimates, such as those used in T/TCP
T/TCP (RFC 1644) [23], can be beneficial. (RFC 1644) [19], can be beneficial.
The Timestamp header (Section 12.39) is used to avoid the The Timestamp header (Section 12.39) is used to avoid the retransmis-
retransmission ambiguity problem [24] and obviates the need for sion ambiguity problem [20] and obviates the need for Karn's algo-
Karn's algorithm. rithm.
Each request carries a sequence number in the CSeq header (Section Each request carries a sequence number in the CSeq header (Section
12.18), which is incremented by one for each distinct request 12.17), which is incremented by one for each distinct request trans-
transmitted. If a request is repeated because of lack of mitted. If a request is repeated because of lack of acknowledgement,
acknowledgement, the request MUST carry the original sequence number the request MUST carry the original sequence number (i.e., the
(i.e., the sequence number is not incremented). sequence number is not incremented).
Systems implementing RTSP MUST support carrying RTSP over TCP and MAY 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 support UDP. The default port for the RTSP server is 554 for both UDP
and TCP. and TCP.
A number of RTSP packets destined for the same control end point may 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 be packed into a single lower-layer PDU or encapsulated into a TCP
stream. RTSP data MAY be interleaved with RTP and RTCP packets. stream. RTSP data MAY be interleaved with RTP and RTCP packets.
Unlike HTTP, an RTSP message MUST contain a Content-Length header Unlike HTTP, an RTSP message MUST contain a Content-Length header
field whenever that message contains a payload. Otherwise, an RTSP field whenever that message contains a payload. Otherwise, an RTSP
packet is terminated with an empty line immediately following the packet is terminated with an empty line immediately following the
last message header. last message header.
10 Method Definitions 10 Method Definitions
The method token indicates the method to be performed on the resource The method token indicates the method to be performed on the resource
identified by the Request-URI case-sensitive. New methods may be identified by the Request-URI case-sensitive. New methods may be
defined in the future. Method names may not start with a $ character defined in the future. Method names may not start with a $ character
(decimal 24) and must be a token. Methods are summarized in Table 2. (decimal 24) and must be a token. Methods are summarized in Table 2.
Notes on 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
method direction object requirement method direction object requirement
__________________________________________________________________ -------------------------------------------------------------
DESCRIBE C -> S P,S recommended DESCRIBE C -> S P,S recommended
ANNOUNCE C -> S, S -> C P,S optional ANNOUNCE C -> S, S -> C P,S optional
GET_PARAMETER C -> S, S -> C P,S optional GET_PARAMETER C -> S, S -> C P,S optional
OPTIONS C -> S, S -> C P,S required (S -> C: optional) OPTIONS C -> S, S -> C P,S required (S -> C: optional)
PAUSE C -> S P,S recommended PAUSE C -> S P,S recommended
PING C->S, S->C P,S optional
PLAY C -> S P,S required PLAY C -> S P,S required
RECORD C -> S P,S optional RECORD C -> S P,S optional
REDIRECT S -> C P,S optional REDIRECT S -> C P,S optional
SETUP C -> S S required SETUP C -> S S required
SET_PARAMETER C -> S, S -> C P,S optional SET_PARAMETER C -> S, S -> C P,S optional
TEARDOWN C -> S P,S required TEARDOWN C -> S P,S required
Table 2: Overview of RTSP methods, their direction, and what objects Table 2: Overview of RTSP methods, their direction, and what objects
(P: presentation, S: stream) they operate on (P: presentation, S: stream) they operate on
Notes on 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 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 request may be issued at any time, e.g., if the client is about to
try a nonstandard request. It does not influence server state. try a nonstandard request. It does not influence server state.
Example: Example:
C->S: OPTIONS * RTSP/1.0 C->S: OPTIONS * RTSP/1.0
CSeq: 1 CSeq: 1
Require: implicit-play Require: implicit-play
Proxy-Require: gzipped-messages Proxy-Require: gzipped-messages
skipping to change at page 1, line 1270 skipping to change at page 1, line 1229
Note that these are necessarily fictional features (one would hope Note that these are necessarily fictional features (one would hope
that we would not purposefully overlook a truly useful feature just that we would not purposefully overlook a truly useful feature just
so that we could have a strong example in this section). so that we could have a strong example in this section).
10.2 DESCRIBE 10.2 DESCRIBE
The DESCRIBE method retrieves the description of a presentation or The DESCRIBE method retrieves the description of a presentation or
media object identified by the request URL from a server. It may use media object identified by the request URL from a server. It may use
the Accept header to specify the description formats that the client the Accept header to specify the description formats that the client
understands. The server responds with a description of the requested understands. The server responds with a description of the requested
resource. The DESCRIBE reply-response pair constitutes the media resource. The DESCRIBE reply-response pair constitutes the media ini-
initialization phase of RTSP. tialization phase of RTSP.
Example: Example:
C->S: DESCRIBE rtsp://server.example.com/fizzle/foo RTSP/1.0 C->S: DESCRIBE rtsp://server.example.com/fizzle/foo RTSP/1.0
CSeq: 312 CSeq: 312
Accept: application/sdp, application/rtsl, application/mheg Accept: application/sdp, application/rtsl, application/mheg
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 312 CSeq: 312
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
skipping to change at page 1, line 1299 skipping to change at page 1, line 1258
u=http://www.cs.ucl.ac.uk/staff/M.Handley/sdp.03.ps u=http://www.cs.ucl.ac.uk/staff/M.Handley/sdp.03.ps
e=mjh@isi.edu (Mark Handley) e=mjh@isi.edu (Mark Handley)
c=IN IP4 224.2.17.12/127 c=IN IP4 224.2.17.12/127
t=2873397496 2873404696 t=2873397496 2873404696
a=recvonly a=recvonly
m=audio 3456 RTP/AVP 0 m=audio 3456 RTP/AVP 0
m=video 2232 RTP/AVP 31 m=video 2232 RTP/AVP 31
m=whiteboard 32416 UDP WB m=whiteboard 32416 UDP WB
a=orient:portrait a=orient:portrait
The DESCRIBE response MUST contain all media initialization The DESCRIBE response MUST contain all media initialization informa-
information for the resource(s) that it describes. If a media client tion for the resource(s) that it describes. If a media client obtains
obtains a presentation description from a source other than DESCRIBE a presentation description from a source other than DESCRIBE and that
and that description contains a complete set of media initialization description contains a complete set of media initialization parame-
parameters, the client SHOULD use those parameters and not then ters, the client SHOULD use those parameters and not then request a
request a description for the same media via RTSP. description for the same media via RTSP.
Additionally, servers SHOULD NOT use the DESCRIBE response as a means Additionally, servers SHOULD NOT use the DESCRIBE response as a means
of media indirection. of media indirection.
By forcing a DESCRIBE response to contain all media By forcing a DESCRIBE response to contain all media initial-
initialization for the set of streams that it describes, ization for the set of streams that it describes, and discour-
and discouraging use of DESCRIBE for media indirection, we aging use of DESCRIBE for media indirection, we avoid looping
avoid looping problems that might result from other problems that might result from other approaches.
approaches.
Media initialization is a requirement for any RTSP-based system, but Media initialization is a requirement for any RTSP-based system, but
the RTSP specification does not dictate that this must be done via the RTSP specification does not dictate that this must be done via
the DESCRIBE method. There are three ways that an RTSP client may the DESCRIBE method. There are three ways that an RTSP client may
receive initialization information: receive initialization information:
o via RTSP's DESCRIBE method; + via RTSP's DESCRIBE method;
o via some other protocol (HTTP, email attachment, etc.); + via some other protocol (HTTP, email attachment, etc.);
o via the command line or standard input (thus working as a + via the command line or standard input (thus working as a browser
browser helper application launched with an SDP file or other helper application launched with an SDP file or other media ini-
media initialization format). tialization format).
It is RECOMMENDED that minimal servers support the DESCRIBE method, It is RECOMMENDED that minimal servers support the DESCRIBE method,
and highly recommended that minimal clients support the ability to and highly recommended that minimal clients support the ability to
act as a "helper application" that accepts a media initialization act as a "helper application" that accepts a media initialization
file from standard input, command line, and/or other means that are file from standard input, command line, and/or other means that are
appropriate to the operating environment of the client. appropriate to the operating environment of the client.
10.3 ANNOUNCE 10.3 ANNOUNCE
The ANNOUNCE method serves two purposes: The ANNOUNCE method serves two purposes:
When sent from client to server, ANNOUNCE posts the description of a When sent from client to server, ANNOUNCE posts the description of a
presentation or media object identified by the request URL to a presentation or media object identified by the request URL to a
server. When sent from server to client, ANNOUNCE updates the server. When sent from server to client, ANNOUNCE updates the ses-
session description in real-time. sion description in real-time.
If a new media stream is added to a presentation (e.g., during a live If a new media stream is added to a presentation (e.g., during a live
presentation), the whole presentation description should be sent presentation), the whole presentation description should be sent
again, rather than just the additional components, so that components again, rather than just the additional components, so that components
can be deleted. can be deleted.
Example: Example:
C->S: ANNOUNCE rtsp://server.example.com/fizzle/foo RTSP/1.0 C->S: ANNOUNCE rtsp://server.example.com/fizzle/foo RTSP/1.0
CSeq: 312 CSeq: 312
skipping to change at page 1, line 1378 skipping to change at page 1, line 1337
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 312 CSeq: 312
10.4 SETUP 10.4 SETUP
The SETUP request for a URI specifies the transport mechanism to be 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 used for the streamed media. A client can issue a SETUP request for a
stream that is already playing to change transport parameters, which stream that is already playing to change transport parameters, which
a server MAY allow. If it does not allow this, it MUST respond with a server MAY allow. If it does not allow this, it MUST respond with
error 455 (Method Not Valid In This State). For the benefit of any error 455 (Method Not Valid In This State). For the benefit of any
intervening firewalls, a client must indicate the transport intervening firewalls, a client must indicate the transport parame-
parameters even if it has no influence over these parameters, for ters even if it has no influence over these parameters, for example,
example, where the server advertises a fixed multicast address. where the server advertises a fixed multicast address.
Since SETUP includes all transport initialization Since SETUP includes all transport initialization information,
information, firewalls and other intermediate network firewalls and other intermediate network devices (which need
devices (which need this information) are spared the more this information) are spared the more arduous task of parsing
arduous task of parsing the DESCRIBE response, which has the DESCRIBE response, which has been reserved for media ini-
been reserved for media initialization. tialization.
The Transport header specifies the transport parameters acceptable The Transport header specifies the transport parameters acceptable to
to the client for data transmission; the response will contain the the client for data transmission; the response will contain the
transport parameters selected by the server. transport parameters selected by the server.
C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0 C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0
CSeq: 302 CSeq: 302
Transport: RTP/AVP;unicast;client_port=4588-4589 Transport: RTP/AVP;unicast;client_port=4588-4589
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 302 CSeq: 302
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
Session: 47112344 Session: 47112344
skipping to change at page 1, line 1402 skipping to change at page 1, line 1361
C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0 C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0
CSeq: 302 CSeq: 302
Transport: RTP/AVP;unicast;client_port=4588-4589 Transport: RTP/AVP;unicast;client_port=4588-4589
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 302 CSeq: 302
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
Session: 47112344 Session: 47112344
Transport: RTP/AVP;unicast; Transport: RTP/AVP;unicast;
client_port=4588-4589;server_port=6256-6257 client_port=4588-4589;server_port=6256-6257
The server generates session identifiers in response to SETUP The server generates session identifiers in response to SETUP
requests. If a SETUP request to a server includes a session requests. If a SETUP request to a server includes a session identi-
identifier, the server MUST bundle this setup request into the fier, the server MUST bundle this setup request into the existing
existing session or return error 459 (Aggregate Operation Not session or return error 459 (Aggregate Operation Not Allowed) (see
Allowed) (see Section 11.4.10). Section 11.4.10).
10.5 PLAY 10.5 PLAY
The PLAY method tells the server to start sending data via the The PLAY method tells the server to start sending data via the mecha-
mechanism specified in SETUP. A client MUST NOT issue a PLAY request nism specified in SETUP. A client MUST NOT issue a PLAY request until
until any outstanding SETUP requests have been acknowledged as any outstanding SETUP requests have been acknowledged as successful.
successful.
The PLAY request positions the normal play time to the beginning of The PLAY request positions the normal play time to the beginning of
the range specified and delivers stream data until the end of the the range specified and delivers stream data until the end of the
range is reached. PLAY requests may be pipelined (queued); a server range is reached. PLAY requests may be pipelined (queued); a server
MUST queue PLAY requests to be executed in order. That is, a PLAY MUST queue PLAY requests to be executed in order. That is, a PLAY
request arriving while a previous PLAY request is still active is request arriving while a previous PLAY request is still active is
delayed until the first has been completed. delayed until the first has been completed.
This allows precise editing. For example, regardless of This allows precise editing. For example, regardless of how
how closely spaced the two PLAY requests in the example closely spaced the two PLAY requests in the example below
below arrive, the server will first play seconds 10 through arrive, the server will first play seconds 10 through 15,
15, then, immediately following, seconds 20 to 25, and then, immediately following, seconds 20 to 25, and finally
finally seconds 30 through the end. seconds 30 through the end.
C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0 C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0
CSeq: 835 CSeq: 835
Session: 12345678 Session: 12345678
Range: npt=10-15 Range: npt=10-15
C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0 C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0
CSeq: 836 CSeq: 836
Session: 12345678 Session: 12345678
Range: npt=20-25 Range: npt=20-25
skipping to change at page 1, line 1449 skipping to change at page 1, line 1406
C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0 C->S: PLAY rtsp://audio.example.com/audio RTSP/1.0
CSeq: 837 CSeq: 837
Session: 12345678 Session: 12345678
Range: npt=30- Range: npt=30-
See the description of the PAUSE request for further examples. See the description of the PAUSE request for further examples.
A PLAY request without a Range header is legal. It starts playing a 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 from the beginning unless the stream has been paused. If a
stream has been paused via PAUSE, stream delivery resumes at the stream has been paused via PAUSE, stream delivery resumes at the
pause point. If a stream is playing, such a PLAY request causes no pause point.
further action and can be used by the client to test server liveness.
The Range header may also contain a time parameter. This parameter The Range header may also contain a time parameter. This parameter
specifies a time in UTC at which the playback should start. If the specifies a time in UTC at which the playback should start. If the
message is received after the specified time, playback is started message is received after the specified time, playback is started
immediately. The time parameter may be used to aid in immediately. The time parameter may be used to aid in synchronization
synchronization of streams obtained from different sources. of streams obtained from different sources.
For a on-demand stream, the server replies with the actual range that For a on-demand stream, the server replies with the actual range that
will be played back. This may differ from the requested range if will be played back. This may differ from the requested range if
alignment of the requested range to valid frame boundaries is alignment of the requested range to valid frame boundaries is
required for the media source. If no range is specified in the required for the media source. If no range is specified in the
request, the current position is returned in the reply. The unit of request, the current position is returned in the reply. The unit of
the range in the reply is the same as that in the request. the range in the reply is the same as that in the request.
After playing the desired range, the presentation is automatically After playing the desired range, the presentation is automatically
paused, as if a PAUSE request had been issued. paused, as if a PAUSE request had been issued.
skipping to change at page 1, line 1481 skipping to change at page 1, line 1437
C->S: PLAY rtsp://audio.example.com/twister.en RTSP/1.0 C->S: PLAY rtsp://audio.example.com/twister.en RTSP/1.0
CSeq: 833 CSeq: 833
Session: 12345678 Session: 12345678
Range: smpte=0:10:20-;time=19970123T153600Z Range: smpte=0:10:20-;time=19970123T153600Z
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 833 CSeq: 833
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
Range: smpte=0:10:22-;time=19970123T153600Z Range: smpte=0:10:22-;time=19970123T153600Z
RTP-Info:url=rtsp://audio.example.com/twister.en;seq=14783;rtptime=2345962545
For playing back a recording of a live presentation, it may be For playing back a recording of a live presentation, it may be desir-
desirable to use clock units: able to use clock units:
C->S: PLAY rtsp://audio.example.com/meeting.en RTSP/1.0 C->S: PLAY rtsp://audio.example.com/meeting.en RTSP/1.0
CSeq: 835 CSeq: 835
Session: 12345678 Session: 12345678
Range: clock=19961108T142300Z-19961108T143520Z Range: clock=19961108T142300Z-19961108T143520Z
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 835 CSeq: 835
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
Range: clock=19961108T142300Z-19961108T143520Z
RTP-Info:url=rtsp://audio.example.com/meeting.en;seq=53745;rtptime=484589019
A media server only supporting playback MUST support the npt format A media server only supporting playback MUST support the npt format
and MAY support the clock and smpte formats. 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 10.6 PAUSE
The PAUSE request causes the stream delivery to be interrupted The PAUSE request causes the stream delivery to be interrupted
(halted) temporarily. If the request URL names a stream, only (halted) temporarily. If the request URL names a stream, only play-
playback and recording of that stream is halted. For example, for back and recording of that stream is halted. For example, for audio,
audio, this is equivalent to muting. If the request URL names a this is equivalent to muting. If the request URL names a presentation
presentation or group of streams, delivery of all currently active or group of streams, delivery of all currently active streams within
streams within the presentation or group is halted. After resuming the presentation or group is halted. After resuming playback or
playback or recording, synchronization of the tracks MUST be recording, synchronization of the tracks MUST be maintained. Any
maintained. Any server resources are kept, though servers MAY close server resources are kept, though servers MAY close the session and
the session and free resources after being paused for the duration free resources after being paused for the duration specified with the
specified with the timeout parameter of the Session header in the timeout parameter of the Session header in the SETUP message.
SETUP message.
Example: Example:
C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0 C->S: PAUSE rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 834 CSeq: 834
Session: 12345678 Session: 12345678
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 834 CSeq: 834
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
The PAUSE request may contain a Range header specifying when the 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 stream or presentation is to be halted. We refer to this point as the |
"pause point". The header must contain exactly one value rather than "pause point". The header must contain a single value, expressed as |
a time range. The normal play time for the stream is set to the pause the beginning value an open range. For example, the following clip |
point. The pause request becomes effective the first time the server will be played from 10 seconds through 21 seconds of the clip's nor- |
is encountering the time point specified in any of the currently mal play time: |
pending PLAY requests. If the Range header specifies a time outside C->S: PLAY rtsp://example.com/fizzle/foo RTSP/1.0 |
any currently pending PLAY requests, the error 457 (Invalid Range) is CSeq: 834 |
returned. If a media unit (such as an audio or video frame) starts Session: 12345678 |
presentation at exactly the pause point, it is not played or Range: npt=10-30 |
recorded. If the Range header is missing, stream delivery is
interrupted immediately on receipt of the message and the pause point S->C: RTSP/1.0 200 OK |
is set to the current normal play time. CSeq: 834 |
Date: 23 Jan 1997 15:35:06 GMT |
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|
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 |
Range: npt=21- |
The normal play time for the stream is set to the pause point. The
pause request becomes effective the first time the server is encoun-
tering the time point specified in any of the currently pending PLAY
requests. If the Range header specifies a time outside any currently
pending PLAY requests, the error 457 (Invalid Range) is 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 play time.
A PAUSE request discards all queued PLAY requests. However, the pause A PAUSE request discards all queued PLAY requests. However, the pause
point in the media stream MUST be maintained. A subsequent PLAY point in the media stream MUST be maintained. A subsequent PLAY
request without Range header resumes from the pause point. request without Range header resumes from the pause point.
For example, if the server has play requests for ranges 10 to 15 and For example, if the server has play requests for ranges 10 to 15 and
20 to 29 pending and then receives a pause request for NPT 21, it 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 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 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 first play request, the server stops immediately. If the pause
request is for NPT 16, the server stops after completing the first request is for NPT 16, the server stops after completing the first
play request and discards the second play request. play request and discards the second play request.
As another example, if a server has received requests to play ranges 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 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 request for NPT=14 would take effect while the server plays the first
range, with the second PLAY request effectively being ignored, range, with the second PLAY request effectively being ignored, assum-
assuming the PAUSE request arrives before the server has started ing the PAUSE request arrives before the server has started playing
playing the second, overlapping range. Regardless of when the PAUSE the second, overlapping range. Regardless of when the PAUSE request
request arrives, it sets the NPT to 14. arrives, it sets the NPT to 14.
If the server has already sent data beyond the time specified in the If the server has already sent data beyond the time specified in the
Range header, a PLAY would still resume at that point in time, as it Range header, a PLAY would still resume at that point in time, as it
is assumed that the client has discarded data after that point. This is assumed that the client has discarded data after that point. This
ensures continuous pause/play cycling without gaps. ensures continuous pause/play cycling without gaps.
10.7 TEARDOWN 10.7 TEARDOWN
The TEARDOWN request stops the stream delivery for the given URI, The TEARDOWN request stops the stream delivery for the given URI,
freeing the resources associated with it. If the URI is the freeing the resources associated with it. If the URI is the presenta-
presentation URI for this presentation, any RTSP session identifier tion URI for this presentation, any RTSP session identifier associ-
associated with the session is no longer valid. Unless all transport ated with the session is no longer valid. Unless all transport param-
parameters are defined by the session description, a SETUP request eters are defined by the session description, a SETUP request has to
has to be issued before the session can be played again. be issued before the session can be played again.
A server that after processing the TEARDOWN still has a valid session
MUST in the response return a session header.
Example: Example:
C->S: TEARDOWN rtsp://example.com/fizzle/foo RTSP/1.0 C->S: TEARDOWN rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 892 CSeq: 892
Session: 12345678 Session: 12345678
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 892 CSeq: 892
skipping to change at page 1, line 1600 skipping to change at page 1, line 1592
Session: 12345678 Session: 12345678
Content-Length: 15 Content-Length: 15
packets_received packets_received
jitter jitter
C->S: RTSP/1.0 200 OK C->S: RTSP/1.0 200 OK
CSeq: 431 CSeq: 431
Content-Length: 46 Content-Length: 46
Content-Type: text/parameters Content-Type: text/parameters
packets_received: 10 packets_received: 10
jitter: 0.3838 jitter: 0.3838
The "text/parameters" section is only an example type for The "text/parameters" section is only an example type for
parameter. This method is intentionally loosely defined parameter. This method is intentionally loosely defined with
with the intention that the reply content and response the intention that the reply content and response content will
content will be defined after further experimentation. be defined after further experimentation.
10.9 SET_PARAMETER 10.9 SET_PARAMETER
This method requests to set the value of a parameter for a This method requests to set the value of a parameter for a presenta-
presentation or stream specified by the URI. tion or stream specified by the URI.
A request SHOULD only contain a single parameter to allow the client A request SHOULD only contain a single parameter to allow the client
to determine why a particular request failed. If the request contains to determine why a particular request failed. If the request contains
several parameters, the server MUST only act on the request if all of several parameters, the server MUST only act on the request if all of
the parameters can be set successfully. A server MUST allow a the parameters can be set successfully. A server MUST allow a parame-
parameter to be set repeatedly to the same value, but it MAY disallow ter to be set repeatedly to the same value, but it MAY disallow
changing parameter values. changing parameter values.
Note: transport parameters for the media stream MUST only be set with Note: transport parameters for the media stream MUST only be set with
the SETUP command. the SETUP command.
Restricting setting transport parameters to SETUP is for Restricting setting transport parameters to SETUP is for the
the benefit of firewalls. benefit of firewalls.
The parameters are split in a fine-grained fashion so that The parameters are split in a fine-grained fashion so that
there can be more meaningful error indications. However, it there can be more meaningful error indications. However, it
may make sense to allow the setting of several parameters may make sense to allow the setting of several parameters if
if an atomic setting is desirable. Imagine device control an atomic setting is desirable. Imagine device control where
where the client does not want the camera to pan unless it the client does not want the camera to pan unless it can also
can also tilt to the right angle at the same time. tilt to the right angle at the same time.
Example: Example:
C->S: SET_PARAMETER rtsp://example.com/fizzle/foo RTSP/1.0 C->S: SET_PARAMETER rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 421 CSeq: 421
Content-length: 20 Content-length: 20
Content-type: text/parameters Content-type: text/parameters
barparam: barstuff barparam: barstuff
S->C: RTSP/1.0 451 Parameter Not Understood S->C: RTSP/1.0 451 Parameter Not Understood
CSeq: 421 CSeq: 421
Content-length: 10 Content-length: 10
Content-type: text/parameters Content-type: text/parameters
barparam barparam
The "text/parameters" section is only an example type for The "text/parameters" section is only an example type for
parameter. This method is intentionally loosely defined parameter. This method is intentionally loosely defined with
with the intention that the reply content and response the intention that the reply content and response content will
content will be defined after further experimentation. be defined after further experimentation.
10.10 REDIRECT 10.10 REDIRECT
A redirect request informs the client that it must connect to another A redirect request informs the client that it must connect to another
server location. It contains the mandatory header Location, which server location. It contains the mandatory header Location, which
indicates that the client should issue requests for that URL. It may indicates that the client should issue requests for that URL. It may
contain the parameter Range, which indicates when the redirection contain the parameter Range, which indicates when the redirection
takes effect. If the client wants to continue to send or receive takes effect. If the client wants to continue to send or receive
media for this URI, the client MUST issue a TEARDOWN request for the media for this URI, the client MUST issue a TEARDOWN request for the
current session and a SETUP for the new session at the designated current session and a SETUP for the new session at the designated
skipping to change at page 1, line 1676 skipping to change at page 1, line 1670
S->C: REDIRECT rtsp://example.com/fizzle/foo RTSP/1.0 S->C: REDIRECT rtsp://example.com/fizzle/foo RTSP/1.0
CSeq: 732 CSeq: 732
Location: rtsp://bigserver.com:8001 Location: rtsp://bigserver.com:8001
Range: clock=19960213T143205Z- Range: clock=19960213T143205Z-
10.11 RECORD 10.11 RECORD
This method initiates recording a range of media data according to This method initiates recording a range of media data according to
the presentation description. The timestamp reflects start and end the presentation description. The timestamp reflects start and end
time (UTC). If no time range is given, use the start or end time time (UTC). If no time range is given, use the start or end time pro-
provided in the presentation description. If the session has already vided in the presentation description. If the session has already
started, commence recording immediately. started, commence recording immediately.
The server decides whether to store the recorded data under the The server decides whether to store the recorded data under the
request-URI or another URI. If the server does not use the request- 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 URI, the response SHOULD be 201 (Created) and contain an entity which
describes the status of the request and refers to the new resource, describes the status of the request and refers to the new resource,
and a Location header. and a Location header.
A media server supporting recording of live presentations MUST A media server supporting recording of live presentations MUST sup-
support the clock range format; the smpte format does not make sense. port the clock range format; the smpte format does not make sense.
In this example, the media server was previously invited to the In this example, the media server was previously invited to the con-
conference indicated. ference indicated.
C->S: RECORD rtsp://example.com/meeting/audio.en RTSP/1.0 C->S: RECORD rtsp://example.com/meeting/audio.en RTSP/1.0
CSeq: 954 CSeq: 954
Session: 12345678 Session: 12345678
Conference: 128.16.64.19/32492374 Conference: 128.16.64.19/32492374
10.12 Embedded (Interleaved) Binary Data Note: this example needs work, or needs to be removed.
10.12 PING |
This method is a bi-directional mechanism for server or client live- |
ness checking. It has no side effects. |
Prior to using this method, an OPTIONS method MUST 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. |
When a proxy is in use, PING with a * indicates a single-hop liveness |
check, whereas PING with a URL indicates an end-to-end liveness |
check. |
Example: |
C->S: PING * RTSP/1.0 |
CSeq: 123 |
S->C: RTSP/1.0 200 OK |
CSeq: 123 |
10.13 Embedded (Interleaved) Binary Data
Certain firewall designs and other circumstances may force a server Certain firewall designs and other circumstances may force a server
to interleave RTSP methods and stream data. This interleaving should to interleave RTSP methods and stream data. This interleaving should
generally be avoided unless necessary since it complicates client and generally be avoided unless necessary since it complicates client and
server operation and imposes additional overhead. Interleaved binary server operation and imposes additional overhead. Interleaved binary
data SHOULD only be used if RTSP is carried over TCP. data SHOULD only be used if RTSP is carried over TCP.
Stream data such as RTP packets is encapsulated by an ASCII dollar Stream data such as RTP packets is encapsulated by an ASCII dollar
sign (24 decimal), followed by a one-byte channel identifier, sign (24 decimal), followed by a one-byte channel identifier, fol-
followed by the length of the encapsulated binary data as a binary, lowed by the length of the encapsulated binary data as a binary, two-
two-byte integer in network byte order. The stream data follows byte integer in network byte order. The stream data follows immedi-
immediately afterwards, without a CRLF, but including the upper-layer ately afterwards, without a CRLF, but including the upper-layer pro-
protocol headers. Each $ block contains exactly one upper-layer tocol headers. Each $ block contains exactly one upper-layer protocol
protocol data unit, e.g., one RTP packet. data unit, e.g., one RTP packet.
The channel identifier is defined in the Transport header with the The channel identifier is defined in the Transport header with the
interleaved parameter(Section 12.40). interleaved parameter(Section 12.40).
When the transport choice is RTP, RTCP messages are also interleaved When the transport choice is RTP, RTCP messages are also interleaved
by the server over the TCP connection. As a default, RTCP packets are 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 sent on the first available channel higher than the RTP channel. The
client MAY explicitly request RTCP packets on another channel. This client MAY explicitly request RTCP packets on another channel. This
is done by specifying two channels in the interleaved parameter of is done by specifying two channels in the interleaved parameter of
the Transport header(Section 12.40). the Transport header(Section 12.40).
RTCP is needed for synchronization when two or more streams RTCP is needed for synchronization when two or more streams
are interleaved in such a fashion. Also, this provides a are interleaved in such a fashion. Also, this provides a con-
convenient way to tunnel RTP/RTCP packets through the TCP venient way to tunnel RTP/RTCP packets through the TCP control
control connection when required by the network connection when required by the network configuration and
configuration and transfer them onto UDP when possible. transfer them onto UDP when possible.
C->S: SETUP rtsp://foo.com/bar.file RTSP/1.0 C->S: SETUP rtsp://foo.com/bar.file RTSP/1.0
CSeq: 2 CSeq: 2
Transport: RTP/AVP/TCP;interleaved=0-1 Transport: RTP/AVP/TCP;interleaved=0-1
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 2 CSeq: 2
Date: 05 Jun 1997 18:57:18 GMT Date: 05 Jun 1997 18:57:18 GMT
Transport: RTP/AVP/TCP;interleaved=0-1 Transport: RTP/AVP/TCP;interleaved=0-1
Session: 12345678 Session: 12345678
skipping to change at page 1, line 1764 skipping to change at page 1, line 1781
11 Status Code Definitions 11 Status Code Definitions
Where applicable, HTTP status [H10] codes are reused. Status codes Where applicable, HTTP status [H10] codes are reused. Status codes
that have the same meaning are not repeated here. See Table 1 for a 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. listing of which status codes may be returned by which requests.
11.1 Success 2xx 11.1 Success 2xx
11.1.1 250 Low on Storage Space 11.1.1 250 Low on Storage Space
The server returns this warning after receiving a RECORD request The server returns this warning after receiving a RECORD request that
that it may not be able to fulfill completely due to insufficient it may not be able to fulfill completely due to insufficient storage
storage space. If possible, the server should use the Range header to space. If possible, the server should use the Range header to indi-
indicate what time period it may still be able to record. Since other cate what time period it may still be able to record. Since other
processes on the server may be consuming storage space processes on the server may be consuming storage space simultane-
simultaneously, a client should take this only as an estimate. ously, a client should take this only as an estimate.
11.2 Redirection 3xx 11.2 Redirection 3xx
See [H10.3]. See [H10.3].
Within RTSP, redirection may be used for load balancing or Within RTSP, redirection may be used for load balancing or redirect-
redirecting stream requests to a server topologically closer to the ing stream requests to a server topologically closer to the client.
client. Mechanisms to determine topological proximity are beyond the Mechanisms to determine topological proximity are beyond the scope of
scope of this specification. this specification.
11.3 Client Error 4xx 11.3 Client Error 4xx
11.4 400 Bad Request 11.4 400 Bad Request
The request could not be understood by the server due to malformed The request could not be understood by the server due to malformed
syntax. The client SHOULD NOT repeat the request without syntax. The client SHOULD NOT repeat the request without modifica-
modifications [H10.4.1]. If the request does not have a CSeq header, tions [H10.4.1]. If the request does not have a CSeq header, the
the server MUST not include a CSeq in the response. server MUST not include a CSeq in the response.
11.4.1 405 Method Not Allowed 11.4.1 405 Method Not Allowed
The method specified in the request is not allowed for the resource The method specified in the request is not allowed for the resource
identified by the request URI. The response MUST include an Allow identified by the request URI. The response MUST include an Allow
header containing a list of valid methods for the requested resource. 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 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 method not indicated during SETUP, e.g., if a RECORD request is
issued even though the mode parameter in the Transport header only issued even though the mode parameter in the Transport header only
specified PLAY. specified PLAY.
11.4.2 451 Parameter Not Understood 11.4.2 451 Parameter Not Understood
The recipient of the request does not support one or more parameters The recipient of the request does not support one or more parameters
contained in the request. contained in the request.
11.4.3 452 Conference Not Found 11.4.3 452 reserved
The conference indicated by a Conference header field is unknown to This error code was removed from RFC 2326 [21] and is obsolete.
the media server.
11.4.4 453 Not Enough Bandwidth 11.4.4 453 Not Enough Bandwidth
The request was refused because there was insufficient bandwidth. The request was refused because there was insufficient bandwidth.
This may, for example, be the result of a resource reservation This may, for example, be the result of a resource reservation fail-
failure. ure.
11.4.5 454 Session Not Found 11.4.5 454 Session Not Found
The RTSP session identifier in the Session header is missing, The RTSP session identifier in the Session header is missing,
invalid, or has timed out. invalid, or has timed out.
11.4.6 455 Method Not Valid in This State 11.4.6 455 Method Not Valid in This State
The client or server cannot process this request in its current The client or server cannot process this request in its current
state. The response SHOULD contain an Allow header to make error state. The response SHOULD contain an Allow header to make error
recovery easier. recovery easier.
11.4.7 456 Header Field Not Valid for Resource 11.4.7 456 Header Field Not Valid for Resource
The server could not act on a required request header. For example, The server could not act on a required request header. For example,
if PLAY contains the Range header field but the stream does not if PLAY contains the Range header field but the stream does not allow
allow seeking. seeking.
11.4.8 457 Invalid Range 11.4.8 457 Invalid Range
The Range value given is out of bounds, e.g., beyond the end of the The Range value given is out of bounds, e.g., beyond the end of the
presentation. presentation.
11.4.9 458 Parameter Is Read-Only 11.4.9 458 Parameter Is Read-Only
The parameter to be set by SET_PARAMETER can be read but not The parameter to be set by SET_PARAMETER can be read but not modi-
modified. fied.
11.4.10 459 Aggregate Operation Not Allowed 11.4.10 459 Aggregate Operation Not Allowed
The requested method may not be applied on the URL in question since 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 it is an aggregate (presentation) URL. The method may be applied on a
stream URL. stream URL.
11.4.11 460 Only Aggregate Operation Allowed 11.4.11 460 Only Aggregate Operation Allowed
The requested method may not be applied on the URL in question since The requested method may not be applied on the URL in question since
it is not an aggregate (presentation) URL. The method may be applied it is not an aggregate (presentation) URL. The method may be applied
on the presentation URL. on the presentation URL.
11.4.12 461 Unsupported Transport 11.4.12 461 Unsupported Transport
The Transport field did not contain a supported transport The Transport field did not contain a supported transport specifica-
specification. tion.
11.4.13 462 Destination Unreachable 11.4.13 462 Destination Unreachable
The data transmission channel could not be established because the The data transmission channel could not be established because the
client address could not be reached. This error will most likely be client address could not be reached. This error will most likely be
the result of a client attempt to place an invalid Destination the result of a client attempt to place an invalid Destination param-
parameter in the Transport field. eter in the Transport field.
11.5 Server Error 5xx 11.5 Server Error 5xx
11.5.1 551 Option not supported 11.5.1 551 Option not supported
An option given in the Require or the Proxy-Require fields was not An option given in the Require or the Proxy-Require fields was not
supported. The Unsupported header should be returned stating the supported. The Unsupported header should be returned stating the
option for which there is no support. option for which there is no support.
12 Header Field Definitions 12 Header Field Definitions
HTTP/1.1 [2] or other, non-standard header fields not listed here The general syntax for header fields is covered in Section 4.2 This |
currently have no well-defined meaning and SHOULD be ignored by the section lists the full set of header fields along with notes on |
recipient. 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?
TEARDOWN C->S P,S required TRD
Table 3 summarizes the header fields used by RTSP. Type "g" Table 3: Overview of RTSP methods, their direction, and what objects
designates general request headers to be found in both requests and (P: presentation, S: stream) they operate on. Body notes if a method
responses, type "R" designates request headers, type "r" designates is allowed to carry body and in which direction, R = Request,
response headers, and type "e" designates entity header fields. r=response. Note: There has been some usage of the body to convey
Fields marked with "req." in the column labeled "support" MUST be more information in error messages for responses containing error
implemented by the recipient for a particular method, while fields codes. Some error messages seem to mandate such usage.
marked "opt." are optional. Note that not all fields marked "req."
will be sent in every request of this type. The "req." means only syntax, meaning, and usage. Throughout this section, we use [HX.Y] |
that client (for response headers) and server (for request headers) to refer to Section X.Y of the current HTTP/1.1 specification RFC |
MUST implement the fields. The last column lists the method for which 2616 [26]. Examples of each header field are given. |
this header field is meaningful; the designation "entity" refers to
all methods that return a message body. Within this specification, Information about header fields in relation to methods and proxy pro- |
DESCRIBE and GET_PARAMETER fall into this class. 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; |
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 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" 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 12.1 Accept
The Accept request-header field can be used to specify certain The Accept request-header field can be used to specify certain pre-
presentation description content types which are acceptable for the sentation description content types which are acceptable for the
response. response.
The "level" parameter for presentation descriptions is The "level" parameter for presentation descriptions is prop-
properly defined as part of the MIME type registration, not erly defined as part of the MIME type registration, not here.
here.
See [H14.1] for syntax. See [H14.1] for syntax.
Example of use: Example of use:
Accept: application/rtsl, application/sdp;level=2 Accept: application/rtsl, application/sdp;level=2
12.2 Accept-Encoding 12.2 Accept-Encoding
See [H14.3] See [H14.3]
12.3 Accept-Language 12.3 Accept-Language
See [H14.4]. Note that the language specified applies to the
presentation description and any reason phrases, not the media
content.
12.4 Accept-Ranges 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 TRD RDR PNG
---------------------------------------------------------------------------------
Accept R o - - - - - - - - - - -
Accept-Encoding R r o - - - - - - - - - - -
Accept-Language R r o - - - - - - - - - - -
Accept-Ranges 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 - - - - - -
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 - - - - - - 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 - - - - - - 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 TRD RDR PNG
Table 4: Overview of RTSP header fields
12.5 Allow 12.5 Allow
The Allow entity-header field lists the methods supported by the The Allow entity-header field lists the methods supported by the
resource identified by the request-URI. The purpose of this field is resource identified by the request-URI. The purpose of this field is
to strictly inform the recipient of valid methods associated with the to strictly inform the recipient of valid methods associated with the
resource. An Allow header field must be present in a 405 (Method Not resource. An Allow header field must be present in a 405 (Method Not
Allowed) response. Allowed) response.
Example of use: Example of use:
skipping to change at page 1, line 1931 skipping to change at page 1, line 2109
resource identified by the request-URI. The purpose of this field is resource identified by the request-URI. The purpose of this field is
to strictly inform the recipient of valid methods associated with the to strictly inform the recipient of valid methods associated with the
resource. An Allow header field must be present in a 405 (Method Not resource. An Allow header field must be present in a 405 (Method Not
Allowed) response. Allowed) response.
Example of use: Example of use:
Allow: SETUP, PLAY, RECORD, SET_PARAMETER Allow: SETUP, PLAY, RECORD, SET_PARAMETER
12.6 Authorization 12.6 Authorization
See [H14.8] See [H14.8]
12.7 Bandwidth 12.7 Bandwidth
The Bandwidth request-header field describes the estimated bandwidth The Bandwidth request-header field describes the estimated bandwidth
available to the client, expressed as a positive integer and measured available to the client, expressed as a positive integer and measured
in bits per second. The bandwidth available to the client may change in bits per second. The bandwidth available to the client may change
during an RTSP session, e.g., due to modem retraining. during an RTSP session, e.g., due to modem retraining.
Bandwidth _ "Bandwidth" ":" 1*DIGIT Bandwidth = "Bandwidth" ":" 1*DIGIT
Example: Example:
Bandwidth: 4000 Bandwidth: 4000
12.8 Blocksize 12.8 Blocksize
The Blocksize request-header field is sent from the client to the The Blocksize request-header field is sent from the client to the
media server asking the server for a particular media packet size. media server asking the server for a particular media packet size.
This packet size does not include lower-layer headers such as IP, 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 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 than the one requested. The server MAY truncate this packet size to
Header type support methods
____________________________________________________________
Accept R opt. entity
Accept-Encoding R opt. entity
Accept-Language R opt. all
Accept-Ranges R opt. all
Allow e opt. all
Authorization R opt. all
Bandwidth R opt. all
Blocksize R opt. all but OPTIONS, TEARDOWN
Cache-Control g opt. SETUP
Conference R opt. SETUP
Connection g req. all
Content-Base e opt. entity
Content-Encoding e req. SET_PARAMETER
Content-Encoding e req. DESCRIBE, ANNOUNCE
Content-Language e req. DESCRIBE, ANNOUNCE
Content-Length e req. SET_PARAMETER, ANNOUNCE
Content-Length e req. entity
Content-Location e opt. entity
Content-Type e req. SET_PARAMETER, ANNOUNCE
CSeq g req. all
Date g opt. all
Expires e opt. DESCRIBE, ANNOUNCE
From R opt. all
If-Match R opt. SETUP
If-Modified-Since R opt. DESCRIBE, SETUP
Last-Modified e opt. entity
Location r opt. 201, 30x
Proxy-Authenticate r req. 407
Proxy-Require R req. all
Public r opt. all
Range R opt. PLAY, PAUSE, RECORD
Range r opt. PLAY, PAUSE, RECORD
Referer R opt. all
Require R req. all
Retry-After r opt. all
RTP-Info r req. PLAY
Scale g opt. PLAY, RECORD
Session g req. all but OPTIONS
Server r opt. all
Speed g opt. PLAY
Transport g req. SETUP
Unsupported r req. all
User-Agent R opt. all
Vary r opt. all
Via g opt. all
WWW-Authenticate r opt. all
Table 3: Overview of RTSP header fields
the closest multiple of the minimum, media-specific block size, or the closest multiple of the minimum, media-specific block size, or
override it with the media-specific size if necessary. The block size override it with the media-specific size if necessary. The block size
MUST be a positive decimal number, measured in octets. The server MUST be a positive decimal number, measured in octets. The server
only returns an error (416) if the value is syntactically invalid. only returns an error (416) if the value is syntactically invalid.
Blocksize _ "Blocksize" ":" 1*DIGIT Blocksize = "Blocksize" ":" 1*DIGIT
12.9 Cache-Control 12.9 Cache-Control
The Cache-Control general-header field is used to specify directives The Cache-Control general-header field is used to specify directives
that MUST be obeyed by all caching mechanisms along the that MUST be obeyed by all caching mechanisms along the
request/response chain. request/response chain.
Cache directives must be passed through by a proxy or gateway Cache directives must be passed through by a proxy or gateway appli-
application, regardless of their significance to that application, cation, regardless of their significance to that application, since
since the directives may be applicable to all recipients along the the directives may be applicable to all recipients along the
request/response chain. It is not possible to specify a cache- request/response chain. It is not possible to specify a cache-direc-
directive for a specific cache. tive for a specific cache.
Cache-Control should only be specified in a SETUP request and its Cache-Control should only be specified in a SETUP request and its
response. Note: Cache-Control does not govern the caching of response. Note: Cache-Control does not govern the caching of
responses as for HTTP, but rather of the stream identified by the responses as for HTTP, but rather of the stream identified by the
SETUP request. Responses to RTSP requests are not cacheable, except SETUP request. Responses to RTSP requests are not cacheable, except
for responses to DESCRIBE. for responses to DESCRIBE.
Cache-Control = "Cache-Control" ":" 1#cache-directive Cache-Control = "Cache-Control" ":" 1#cache-directive
cache-directive = cache-request-directive cache-directive = cache-request-directive
| cache-response-directive | cache-response-directive
skipping to change at page 1, line 2046 skipping to change at page 1, line 2173
| cache-extension | cache-extension
cache-response-directive = "public" cache-response-directive = "public"
| "private" | "private"
| "no-cache" | "no-cache"
| "no-transform" | "no-transform"
| "must-revalidate" | "must-revalidate"
| "proxy-revalidate" | "proxy-revalidate"
| "max-age" "=" delta-seconds | "max-age" "=" delta-seconds
| cache-extension | cache-extension
cache-extension = token [ "=" ( token | quoted-string ) ] cache-extension = token [ "=" ( token | quoted-string ) ]
no-cache: Indicates that the media stream MUST NOT be cached
anywhere. 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 no-cache: Indicates that the media stream MUST NOT be cached any-
cache. where. This allows an origin server to prevent caching even by
caches that have been configured to return stale responses to
private: Indicates that the media stream is intended for a client requests.
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 public: Indicates that the media stream is cacheable by any cache.
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 operational 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 authentication 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 private: Indicates that the media stream is intended for a single
network connectivity, a client may want a cache to return user and MUST NOT be cached by a shared cache. A private (non-
only those media streams that it currently has stored, and shared) cache may cache the media stream.
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 constraints of the request, or
respond with a 504 (Gateway Timeout) 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 no-transform: An intermediate cache (proxy) may find it useful to
media stream that has exceeded its expiration time. If convert the media type of a certain stream. A proxy might, for
max-stale is assigned a value, then the client is willing example, convert between video formats to save cache space or
to accept a response that has exceeded its expiration time to reduce the amount of traffic on a slow link. Serious opera-
by no more than the specified number of seconds. If no tional problems may occur, however, when these transformations
value is assigned to max-stale, then the client is willing have been applied to streams intended for certain kinds of
to accept a stale response of any age. 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.
min-fresh: Indicates that the client is willing to accept a only-if-cached: In some cases, such as times of extremely poor net-
media stream whose freshness lifetime is no less than its work connectivity, a client may want a cache to return only
current age plus the specified time in seconds. That is, those media streams that it currently has stored, and not to
the client wants a response that will still be fresh for at receive these from the origin server. To do this, the client
least the specified number of seconds. 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.
must-revalidate: When the must-revalidate directive is present max-stale: Indicates that the client is willing to accept a media
in a SETUP response received by a cache, that cache MUST stream that has exceeded its expiration time. If max-stale is
NOT use the entry after it becomes stale to respond to a assigned a value, then the client is willing to accept a
subsequent request without first revalidating it with the response that has exceeded its expiration time by no more than
origin server. That is, the cache must do an end-to-end the specified number of seconds. If no value is assigned to
revalidation every time, if, based solely on the origin max-stale, then the client is willing to accept a stale
server's Expires, the cached response is stale.) response of any age.
12.10 Conference 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.
The Conference request-header field establishes a logical connection must-revalidate: When the must-revalidate directive is present in a
between a pre-established conference and an RTSP stream. The SETUP response received by a cache, that cache MUST NOT use
conference-id must not be changed for the same RTSP session. 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.)
Conference _ "Conference" ":" conference-id 12.10 Connection
Example: See [H14.10]
Conference: 199702170042.SAA08642@obiwan.arl.wustl.edu%20Starr 12.11 Content-Base
A response code of 452 (Conference Not Found) is returned if the The Content-Base entity-header field may be used to specify the base
conference-id is not valid. URI for resolving relative URLs within the entity. This header field
is described as Base in RFC 1808, which is expected to be revised.
12.11 Connection Content-Base = "Content-Base" ":" absoluteURI
See [H14.10] 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-Base 12.12 Content-Encoding
See [H14.11] See [H14.11]
12.13 Content-Encoding 12.13 Content-Language
See [H14.12] See [H14.12]
12.14 Content-Language 12.14 Content-Length
See [H14.13]
12.15 Content-Length
The Content-Length general-header field contains the length of the The Content-Length general-header field contains the length of the
content of the method (i.e. after the double CRLF following the last 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 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 content beyond the header portion of the message. If it is missing, a
default value of zero is assumed. It is interpreted according to default value of zero is assumed. It is interpreted according to
[H14.14]. [H14.13].
12.16 Content-Location 12.15 Content-Location
See [H14.15] See [H14.14]
12.17 Content-Type 12.16 Content-Type
See [H14.18]. Note that the content types suitable for RTSP are See [H14.17]. Note that the content types suitable for RTSP are
likely to be restricted in practice to presentation descriptions and likely to be restricted in practice to presentation descriptions and
parameter-value types. parameter-value types.
12.18 CSeq 12.17 CSeq
The CSeq general-header field specifies the sequence number for an The CSeq general-header field specifies the sequence number for an
RTSP request-response pair. This field MUST be present in all RTSP request-response pair. This field MUST be present in all
requests and responses. For every RTSP request containing the given requests and responses. For every RTSP request containing the given
sequence number, the corresponding response will have the same sequence number, the corresponding response will have the same num-
number. Any retransmitted request must contain the same sequence ber. Any retransmitted request must contain the same sequence number
number as the original (i.e. the sequence number is not incremented as the original (i.e. the sequence number is not incremented for
for retransmissions of the same request). retransmissions of the same request).
CSeq _ "Cseq" ":" 1*DIGIT CSeq = "Cseq" ":" 1*DIGIT
12.19 Date 12.18 Date
See [H14.19]. See [H14.18].
12.20 Expires 12.19 Expires
The Expires entity-header field gives a date and time after which The Expires entity-header field gives a date and time after which the
the description or media-stream should be considered stale. The description or media-stream should be considered stale. The interpre-
interpretation depends on the method: tation depends on the method:
DESCRIBE response: The Expires header indicates a date and time DESCRIBE response: The Expires header indicates a date and time
after which the description should be considered stale. after which the description should be considered stale.
A stale cache entry may not normally be returned by a cache (either a 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 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 the origin server (or with an intermediate cache that has a fresh
copy of the entity). See section 13 for further discussion of the copy of the entity). See section 13 for further discussion of the
expiration model. expiration model.
The presence of an Expires field does not imply that the original The presence of an Expires field does not imply that the original
resource will change or cease to exist at, before, or after that resource will change or cease to exist at, before, or after that
time. time.
The format is an absolute date and time as defined by HTTP-date in The format is an absolute date and time as defined by HTTP-date in
[H3.3]; it MUST be in RFC1123-date format: [H3.3]; it MUST be in RFC1123-date format:
Expires _ "Expires" ":" HTTP-date Expires = "Expires" ":" HTTP-date
An example of its use is An example of its use is
Expires: Thu, 01 Dec 1994 16:00:00 GMT Expires: Thu, 01 Dec 1994 16:00:00 GMT
RTSP/1.0 clients and caches MUST treat other invalid date formats, RTSP/1.0 clients and caches MUST treat other invalid date formats,
especially including the value "0", as having occurred in the past especially including the value "0", as having occurred in the past
(i.e., already expired). (i.e., already expired).
To mark a response as "already expired," an origin server should use To mark a response as "already expired," an origin server should use
skipping to change at page 1, line 2211 skipping to change at page 1, line 2332
Expires: Thu, 01 Dec 1994 16:00:00 GMT Expires: Thu, 01 Dec 1994 16:00:00 GMT
RTSP/1.0 clients and caches MUST treat other invalid date formats, RTSP/1.0 clients and caches MUST treat other invalid date formats,
especially including the value "0", as having occurred in the past especially including the value "0", as having occurred in the past
(i.e., already expired). (i.e., already expired).
To mark a response as "already expired," an origin server should use To mark a response as "already expired," an origin server should use
an Expires date that is equal to the Date header value. To mark a an Expires date that is equal to the Date header value. To mark a
response as "never expires," an origin server should use an Expires response as "never expires," an origin server should use an Expires
date approximately one year from the time the response is sent. 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 RTSP/1.0 servers should not send Expires dates more than one year in
the future. the future.
The presence of an Expires header field with a date value of some 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 time in the future on a media stream that otherwise would by default
be non-cacheable indicates that the media stream is cacheable, unless be non-cacheable indicates that the media stream is cacheable, unless
indicated otherwise by a Cache-Control header field (Section 12.9). indicated otherwise by a Cache-Control header field (Section 12.9).
12.21 From 12.20 From
See [H14.22]. See [H14.22].
12.22 Host 12.21 Host
The Host HTTP request header field is not needed for RTSP. It should The Host HTTP request header field [H14.23] is not needed for RTSP.
be silently ignored if sent. It should be silently ignored if sent.
12.23 If-Match 12.22 If-Match
See [H14.25].
See [H14.24].
The If-Match request-header field is especially useful for ensuring The If-Match request-header field is especially useful for ensuring
the integrity of the presentation description, in both the case where 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 it is fetched via means external to RTSP (such as HTTP), or in the
case where the server implementation is guaranteeing the integrity of case where the server implementation is guaranteeing the integrity of
the description between the time of the DESCRIBE message and the the description between the time of the DESCRIBE message and the
SETUP message. SETUP message.
The identifier is an opaque identifier, and thus is not specific to The identifier is an opaque identifier, and thus is not specific to
any particular session description language. any particular session description language.
12.24 If-Modified-Since 12.23 If-Modified-Since
The If-Modified-Since request-header field is used with the DESCRIBE The If-Modified-Since request-header field is used with the DESCRIBE
and SETUP methods to make them conditional. If the requested variant and SETUP methods to make them conditional. If the requested variant
has not been modified since the time specified in this field, a has not been modified since the time specified in this field, a
description will not be returned from the server (DESCRIBE) or a description will not be returned from the server (DESCRIBE) or a
stream will not be set up (SETUP). Instead, a 304 (Not Modified) stream will not be set up (SETUP). Instead, a 304 (Not Modified)
response will be returned without any message-body. response will be returned without any message-body.
If-Modified-Since _ "If-Modified-Since" ":" HTTP-date If-Modified-Since = "If-Modified-Since" ":" HTTP-date
An example of the field is: An example of the field is:
If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT
12.25 Last-Modified 12.24 Last-Modified
The Last-Modified entity-header field indicates the date and time at The Last-Modified entity-header field indicates the date and time at
which the origin server believes the presentation description or which the origin server believes the presentation description or
media stream was last modified. See [H14.29]. For the methods media stream was last modified. See [H14.29]. For the methods
DESCRIBE or ANNOUNCE, the header field indicates the last DESCRIBE or ANNOUNCE, the header field indicates the last modifica-
modification date and time of the description, for SETUP that of the tion date and time of the description, for SETUP that of the media
media stream. stream.
12.26 Location 12.25 Location
See [H14.30]. See [H14.30].
12.27 Proxy-Authenticate 12.26 Proxy-Authenticate
See [H14.33]. See [H14.33].
12.28 Proxy-Require 12.27 Proxy-Require
The Proxy-Require request-header field is used to indicate proxy- The Proxy-Require request-header field is used to indicate proxy-sen-
sensitive features that MUST be supported by the proxy. Any Proxy- sitive features that MUST be supported by the proxy. Any Proxy-
Require header features that are not supported by the proxy MUST be Require header features that are not supported by the proxy MUST be
negatively acknowledged by the proxy to the client if not supported. negatively acknowledged by the proxy to the client if not supported.
Servers should treat this field identically to the Require field. Servers should treat this field identically to the Require field.
See Section 12.33 for more details on the mechanics of this message See Section 12.32 for more details on the mechanics of this message
and a usage example. and a usage example.
12.29 Public 12.28 Public
See [H14.35]. The Public response-header field lists the set of methods supported
by the server. The purpose of this field is strictly to inform the
recipient of the capabilities of the server regarding unusual meth-
ods. The methods listed may or may not be applicable to the Request-
URI; the Allow header field (section 14.7) MAY be used to indicate
methods allowed for a particular URI.
12.30 Range Public = "Public" ":" 1#method
Example of use:
Public: OPTIONS, MGET, MHEAD, GET, HEAD
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 The Range request and response header field specifies a range of
time. The range can be specified in a number of units. This time. The range can be specified in a number of units. This specifi-
specification defines the smpte (Section 3.5), npt (Section 3.6), cation defines the smpte (Section 3.4), npt (Section 3.5), and clock
and clock (Section 3.7) range units. Within RTSP, byte ranges (Section 3.6) range units. Within RTSP, byte ranges [H14.35.1] are
[H14.36.1] are not meaningful and MUST NOT be used. The header may not meaningful and MUST NOT be used. The header may also contain a
also contain a time parameter in UTC, specifying the time at which time parameter in UTC, specifying the time at which the operation is
the operation is to be made effective. Servers supporting the Range to be made effective. Servers supporting the Range header MUST under-
header MUST understand the NPT range format and SHOULD understand the stand the NPT range format and SHOULD understand the SMPTE range for-
SMPTE range format. The Range response header indicates what range mat. The Range response header indicates what range of time is actu-
of time is actually being played or recorded. If the Range header is ally being played or recorded. If the Range header is given in a time
given in a time format that is not understood, the recipient should format that is not understood, the recipient should return 501 (Not
return 501 (Not Implemented). Implemented).
Ranges are half-open intervals, including the lower point, but Ranges are half-open intervals, including the lower point, but
excluding the upper point. In other words, a range of a-b starts excluding the upper point. In other words, a range of a-b starts
exactly at time a, but stops just before b. Only the start time of a exactly at time a, but stops just before b. Only the start time of a
media unit such as a video or audio frame is relevant. As an example, media unit such as a video or audio frame is relevant. As an example,
assume that video frames are generated every 40 ms. A range of assume that video frames are generated every 40 ms. A range of
10.0-10.1 would include a video frame starting at 10.0 or later time 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 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, lasted beyond the interval. A range of 10.0-10.08, on the other hand,
would exclude the frame at 10.08. would exclude the frame at 10.08.
Range _ "Range" ":" 1#ranges-specifier [ ";" "time" "=" utc-time ] Range = "Range" ":" 1#ranges-specifier [ ";" "time" "=" utc-time ]
ranges-specifier _ npt-range | utc-range | smpte-range ranges-specifier = npt-range | utc-range | smpte-range
Example: Example:
Range: clock=19960213T143205Z-;time=19970123T143720Z Range: clock=19960213T143205Z-;time=19970123T143720Z
The notation is similar to that used for the HTTP/1.1 [2]
byte-range header. It allows clients to select an excerpt
from the media object, and to play from a given point to
the end as well as from the current location to a given
point. The start of playback can be scheduled for any time
in the future, although a server may refuse to keep server
resources for extended idle periods.
12.31 Referer The notation is similar to that used for the HTTP/1.1 [26]
byte-range header. It allows clients to select an excerpt from
the media object, and to play from a given point to the end as
well as from the current location to a given point. The start
of playback can be scheduled for any time in the future,
although a server may refuse to keep server resources for
extended idle periods.
See [H14.37]. The URL refers to that of the presentation description, 12.30 Referer
See [H14.36]. The URL refers to that of the presentation description,
typically retrieved via HTTP. typically retrieved via HTTP.
12.32 Retry-After 12.31 Retry-After
See [H14.38]. See [H14.37].
12.33 Require 12.32 Require
The Require request-header field is used by clients to query the The Require request-header field is used by clients to query the
server about options that it may or may not support. The server MUST server about options that it may or may not support. The server MUST
respond to this header by using the Unsupported header to negatively respond to this header by using the Unsupported header to negatively
acknowledge those options which are NOT supported. acknowledge those options which are NOT supported.
This is to make sure that the client-server interaction This is to make sure that the client-server interaction will
will proceed without delay when all options are understood proceed without delay when all options are understood by both
by both sides, and only slow down if options are not sides, and only slow down if options are not understood (as in
understood (as in the case above). For a well-matched the case above). For a well-matched client-server pair, the
client-server pair, the interaction proceeds quickly, interaction proceeds quickly, saving a round-trip often
saving a round-trip often required by negotiation required by negotiation mechanisms. In addition, it also
mechanisms. In addition, it also removes state ambiguity removes state ambiguity when the client requires features that
when the client requires features that the server does not the server does not understand.
understand.
Require _ "Require" ":" 1#option-tag Require = "Require" ":" 1#option-tag
Example: Example:
C->S: SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0 C->S: SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0
CSeq: 302 CSeq: 302
Require: funky-feature Require: funky-feature
Funky-Parameter: funkystuff Funky-Parameter: funkystuff
S->C: RTSP/1.0 551 Option not supported S->C: RTSP/1.0 551 Option not supported
CSeq: 302 CSeq: 302
skipping to change at page 1, line 2371 skipping to change at page 1, line 2512
S->C: RTSP/1.0 551 Option not supported S->C: RTSP/1.0 551 Option not supported
CSeq: 302 CSeq: 302
Unsupported: funky-feature Unsupported: funky-feature
C->S: SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0 C->S: SETUP rtsp://server.com/foo/bar/baz.rm RTSP/1.0
CSeq: 303 CSeq: 303
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 303 CSeq: 303
In this example, "funky-feature" is the feature tag which indicates In this example, "funky-feature" is the feature tag which indicates
to the client that the fictional Funky-Parameter field is required. to the client that the fictional Funky-Parameter field is required.
The relationship between "funky-feature" and Funky-Parameter is not The relationship between "funky-feature" and Funky-Parameter is not
communicated via the RTSP exchange, since that relationship is an communicated via the RTSP exchange, since that relationship is an
immutable property of "funky-feature" and thus should not be immutable property of "funky-feature" and thus should not be trans-
transmitted with every exchange. mitted with every exchange.
Proxies and other intermediary devices SHOULD ignore features that Proxies and other intermediary devices SHOULD ignore features that
are not understood in this field. If a particular extension requires are not understood in this field. If a particular extension requires
that intermediate devices support it, the extension should be tagged that intermediate devices support it, the extension should be tagged
in the Proxy-Require field instead (see Section 12.28). in the Proxy-Require field instead (see Section 12.27).
12.34 RTP-Info 12.33 RTP-Info
The RTP-Info response-header field is used to set RTP-specific The RTP-Info response-header field is used to set RTP-specific param-
parameters in the PLAY response. eters in the PLAY response.
url: Indicates the stream URL which for which the following RTP url: Indicates the stream URL which for which the following RTP
parameters correspond. parameters correspond.
seq: Indicates the sequence number of the first packet of the seq: Indicates the sequence number of the first packet of the
stream. This allows clients to gracefully deal with packets stream. This allows clients to gracefully deal with packets
when seeking. The client uses this value to differentiate when seeking. The client uses this value to differentiate
packets that originated before the seek from packets that packets that originated before the seek from packets that
originated after the seek. originated after the seek.
rtptime: Indicates the RTP timestamp corresponding to the time rtptime: Indicates the RTP timestamp corresponding to the time
value in the Range response header. (Note: For aggregate value in the Range response header. (Note: For aggregate con-
control, a particular stream may not actually generate a trol, a particular stream may not actually generate a packet
packet for the Range time value returned or implied. Thus, for the Range time value returned or implied. Thus, there is
there is no guarantee that the packet with the sequence no guarantee that the packet with the sequence number indi-
number indicated by seq actually has the timestamp cated by seq actually has the timestamp indicated by rtptime.)
indicated by rtptime.) The client uses this value to The client uses this value to calculate the mapping of RTP
calculate the mapping of RTP time to NPT. time to NPT.
A mapping from RTP timestamps to NTP timestamps (wall A mapping from RTP timestamps to NTP timestamps (wall
clock) is available via RTCP. However, this clock) is available via RTCP. However, this information
information is not sufficient to generate a mapping is not sufficient to generate a mapping from RTP times-
from RTP timestamps to NPT. Furthermore, in order to tamps to NPT. Furthermore, in order to ensure that this
ensure that this information is available at the information is available at the necessary time (immedi-
necessary time (immediately at startup or after a ately at startup or after a seek), and that it is deliv-
seek), and that it is delivered reliably, this mapping ered reliably, this mapping is placed in the RTSP control
is placed in the RTSP control channel. channel.
In order to compensate for drift for long, uninterrupted In order to compensate for drift for long, uninterrupted pre-
presentations, RTSP clients should additionally map NPT to sentations, RTSP clients should additionally map NPT to NTP,
NTP, using initial RTCP sender reports to do the mapping, using initial RTCP sender reports to do the mapping, and later
and later reports to check drift against the mapping. reports to check drift against the mapping.
Syntax: Syntax:
RTP-Info ______________________________ "RTP-Info" ":" 1#rtsp-info-spec RTP-Info = "RTP-Info" ":" 1#rtsp-info-spec
rtsp-info-spec ______________________________ stream-url 1*parameter rtsp-info-spec = stream-url 1*parameter
stream-url ______________________________ quoted-url | unquoted-url stream-url = quoted-url | unquoted-url
unquoted-url ______________________________ "url" "=" safe-url unquoted-url = "url" "=" safe-url
| ";" "mode" = <"> 1#Method <"> | ";" "mode" = <"> 1#Method <">
quoted-url ______________________________ "url" "=" <"> needquote-url <"> quoted-url = "url" "=" <"> needquote-url <">
safe-url ______________________________ url safe-url = url
needquote-url ______________________________ url needquote-url = url
url ______________________________ ( absoluteURI | relativeURI ) url = ( absoluteURI | relativeURI )
parameter ______________________________ ";" "seq" "=" 1*DIGIT parameter = ";" "seq" "=" 1*DIGIT
| ";" "rtptime" "=" 1*DIGIT | ";" "rtptime" "=" 1*DIGIT
Additional constraint: safe-url MUST NOT contain the semicolon (";") Additional constraint: safe-url MUST NOT contain the semicolon (";")
or comma (",") characters. The quoted-url form SHOULD only be used or comma (",") characters. The quoted-url form SHOULD only be used
when a URL does not meet the safe-url constraint, in order to ensure when a URL does not meet the safe-url constraint, in order to ensure
compatibility with implementations conformant to RFC 2326 [25]. compatibility with implementations conformant to RFC 2326 [21].
absoluteURI and relativeURI are defined in RFC 2396 [26]. absoluteURI and relativeURI are defined in RFC 2396 [22].
Example: Example:
RTP-Info: url=rtsp://foo.com/bar.avi/streamid=0;seq=45102, RTP-Info: url=rtsp://foo.com/bar.avi/streamid=0;seq=45102,
url=rtsp://foo.com/bar.avi/streamid=1;seq=30211 url=rtsp://foo.com/bar.avi/streamid=1;seq=30211
12.35 Scale 12.34 Scale
A scale value of 1 indicates normal play or record at the normal A scale value of 1 indicates normal play or record at the normal for-
forward viewing rate. If not 1, the value corresponds to the rate ward viewing rate. If not 1, the value corresponds to the rate with
with respect to normal viewing rate. For example, a ratio of 2 respect to normal viewing rate. For example, a ratio of 2 indicates
indicates twice the normal viewing rate ("fast forward") and a ratio twice the normal viewing rate ("fast forward") and a ratio of 0.5
of 0.5 indicates half the normal viewing rate. In other words, a indicates half the normal viewing rate. In other words, a ratio of 2
ratio of 2 has normal play time increase at twice the wallclock rate. has normal play time increase at twice the wallclock rate. For every
For every second of elapsed (wallclock) time, 2 seconds of content second of elapsed (wallclock) time, 2 seconds of content will be
will be delivered. A negative value indicates reverse direction. delivered. A negative value indicates reverse direction.
Unless requested otherwise by the Speed parameter, the data rate Unless requested otherwise by the Speed parameter, the data rate
SHOULD not be changed. Implementation of scale changes depends on the SHOULD not be changed. Implementation of scale changes depends on the
server and media type. For video, a server may, for example, deliver server and media type. For video, a server may, for example, deliver
only key frames or selected key frames. For audio, it may time-scale only key frames or selected key frames. For audio, it may time-scale
the audio while preserving pitch or, less desirably, deliver the audio while preserving pitch or, less desirably, deliver frag-
fragments of audio. ments of audio.
The server should try to approximate the viewing rate, but may The server should try to approximate the viewing rate, but may
restrict the range of scale values that it supports. The response restrict the range of scale values that it supports. The response
MUST contain the actual scale value chosen by the server. MUST contain the actual scale value chosen by the server.
If the request contains a Range parameter, the new scale value will If the request contains a Range parameter, the new scale value will
take effect at that time. take effect at that time.
Scale _ "Scale" ":" [ "-" ] 1*DIGIT [ "." *DIGIT ] Scale = "Scale" ":" [ "-" ] 1*DIGIT [ "." *DIGIT ]
Example of playing in reverse at 3.5 times normal rate: Example of playing in reverse at 3.5 times normal rate:
Scale: -3.5 Scale: -3.5
12.36 Speed 12.35 Speed
The Speed request-header field requests the server to deliver data The Speed request-header field requests the server to deliver data to
to the client at a particular speed, contingent on the server's the client at a particular speed, contingent on the server's ability
ability and desire to serve the media stream at the given speed. and desire to serve the media stream at the given speed. Implementa-
Implementation by the server is OPTIONAL. The default is the bit rate tion by the server is OPTIONAL. The default is the bit rate of the
of the stream. stream.
The parameter value is expressed as a decimal ratio, e.g., a value of The parameter value is expressed as a decimal ratio, e.g., a value of
2.0 indicates that data is to be delivered twice as fast as normal. A 2.0 indicates that data is to be delivered twice as fast as normal. A
speed of zero is invalid. If the request contains a Range parameter, speed of zero is invalid. If the request contains a Range parameter,
the new speed value will take effect at that time. the new speed value will take effect at that time.
Speed = "Speed" ":" 1*DIGIT [ "." *DIGIT ] Speed = "Speed" ":" 1*DIGIT [ "." *DIGIT ]
Example: Example:
Speed: 2.5 Speed: 2.5
Use of this field changes the bandwidth used for data delivery. It is Use of this field changes the bandwidth used for data delivery. It is
meant for use in specific circumstances where preview of the meant for use in specific circumstances where preview of the presen-
presentation at a higher or lower rate is necessary. Implementors tation at a higher or lower rate is necessary. Implementors should
should keep in mind that bandwidth for the session may be negotiated keep in mind that bandwidth for the session may be negotiated before-
beforehand (by means other than RTSP), and therefore re-negotiation hand (by means other than RTSP), and therefore re-negotiation may be
may be necessary. When data is delivered over UDP, it is highly necessary. When data is delivered over UDP, it is highly recommended
recommended that means such as RTCP be used to track packet loss that means such as RTCP be used to track packet loss rates.
rates.
12.37 Server 12.36 Server
See [H14.39] See [H14.38]
12.38 Session 12.37 Session
The Session request-header and response-header field identifies an The Session request-header and response-header field identifies an
RTSP session started by the media server in a SETUP response and RTSP session started by the media server in a SETUP response and con-
concluded by TEARDOWN on the presentation URL. The session cluded by TEARDOWN on the presentation URL. The session identifier is
identifier is chosen by the media server (see Section 3.4) and MUST chosen by the media server (see Section 3.3) and MUST be returned in
be returned in the SETUP response. Once a client receives a Session the SETUP response. Once a client receives a Session identifier, it
identifier, it MUST return it for any request related to that MUST return it for any request related to that session.
session.
Session _ "Session" ":" session-id [ ";" "timeout" "=" delta-seconds ] Session = "Session" ":" session-id [ ";" "timeout" "=" delta-seconds ]
The timeout parameter is only allowed in a response header. The The timeout parameter is only allowed in a response header. The
server uses it to indicate to the client how long the server is server uses it to indicate to the client how long the server is pre-
prepared to wait between RTSP commands before closing the session due pared to wait between RTSP commands before closing the session due to
to lack of activity (see Section A). The timeout is measured in lack of activity (see Section A). The timeout is measured in seconds,
seconds, with a default of 60 seconds (1 minute). with a default of 60 seconds (1 minute).
Note that a session identifier identifies an RTSP session across Note that a session identifier identifies an RTSP session across
transport sessions or connections. Control messages for more than one transport sessions or connections. Control messages for more than one
RTSP URL may be sent within a single RTSP session. Hence, it is RTSP URL may be sent within a single RTSP session. Hence, it is pos-
possible that clients use the same session for controlling many sible that clients use the same session for controlling many streams
streams constituting a presentation, as long as all the streams come constituting a presentation, as long as all the streams come from the
from the same server. (See example in Section 14). However, multiple same server. (See example in Section 14). However, multiple "user"
"user" sessions for the same URL from the same client MUST use sessions for the same URL from the same client MUST use different
different session identifiers. session identifiers.
The session identifier is needed to distinguish several The session identifier is needed to distinguish several deliv-
delivery requests for the same URL coming from the same ery requests for the same URL coming from the same client.
client.
The response 454 (Session Not Found) is returned if the session The response 454 (Session Not Found) is returned if the session iden-
identifier is invalid. tifier is invalid.
12.38 Supported |
The Supported header field enumerates all the extensions supported by |
the client or server. When offered in a request, the receiver MUST |
respond with its cooresponding Supported header. |
The Supported header field contains a list of option tags, described |
in Section 3.7, that are understood by the client or server. |
Example: |
C->S OPTIONS rtsp://example.com/ RTSP/1.0 ||
Supported: foo, bar, blech ||
SuppoS->C:RTSP/1.0e200 OKz ||
12.39 Timestamp 12.39 Timestamp
The Timestamp general-header field describes when the client sent The Timestamp general-header field describes when the client sent the
the request to the server. The value of the timestamp is of request to the server. The value of the timestamp is of significance
significance only to the client and may use any timescale. The server only to the client and may use any timescale. The server MUST echo
MUST echo the exact same value and MAY, if it has accurate the exact same value and MAY, if it has accurate information about
information about this, add a floating point number indicating the this, add a floating point number indicating the number of seconds
number of seconds that has elapsed since it has received the request. that has elapsed since it has received the request. The timestamp is
The timestamp is used by the client to compute the round-trip time to used by the client to compute the round-trip time to the server so
the server so that it can adjust the timeout value for that it can adjust the timeout value for retransmissions.
retransmissions.
Timestamp _ "Timestamp" ":" *(DIGIT) [ "." *(DIGIT) ] [ delay ] Timestamp = "Timestamp" ":" *(DIGIT) [ "." *(DIGIT) ] [ delay ]
delay _ *(DIGIT) [ "." *(DIGIT) ] delay = *(DIGIT) [ "." *(DIGIT) ]
12.40 Transport 12.40 Transport
The Transport request-header field indicates which transport The Transport request-header field indicates which transport protocol
protocol is to be used and configures its parameters such as is to be used and configures its parameters such as destination
destination address, compression, multicast time-to-live and address, compression, multicast time-to-live and destination port for
destination port for a single stream. It sets those values not a single stream. It sets those values not already determined by a
already determined by a presentation description. presentation description.
Transports are comma separated, listed in order of preference. Transports are comma separated, listed in order of preference.
Parameters may be added to each transport, separated by a semicolon. Parameters may be added to each transport, separated by a semicolon.
The Transport header field MAY also be used to change certain The Transport header field MAY also be used to change certain trans-
transport parameters. A server MAY refuse to change parameters of an port parameters. A server MAY refuse to change parameters of an
existing stream. existing stream.
The server MAY return a Transport response-header field in the The server MAY return a Transport response-header field in the
response to indicate the values actually chosen. response to indicate the values actually chosen.
A Transport request header field may contain a list of transport A Transport request header field may contain a list of transport
options acceptable to the client, in the form of multiple transport- options acceptable to the client, in the form of multiple transport-
spec entries. In that case, the server MUST return a single option ( spec entries. In that case, the server MUST return a single option
transport-spec) which was actually chosen. (transport-spec) which was actually chosen.
A transport-spec transport option may only contain one of any given A transport-spec transport option may only contain one of any given |
parameter within it. Parameters may be given in any order. parameter within it. Parameters may be given in any order. Addition- |
Additionally, it may only contain the unicast or multicast transport ally, it may only contain the unicast or multicast transport parame- |
parameter. ter.
The Transport header field is restricted to describing a The Transport header field is restricted to describing a sin-
single RTP stream. (RTSP can also control multiple streams gle RTP stream. (RTSP can also control multiple streams as a
as a single entity.) Making it part of RTSP rather than single entity.) Making it part of RTSP rather than relying on
relying on a multitude of session description formats a multitude of session description formats greatly simplifies
greatly simplifies designs of firewalls. designs of firewalls.
The syntax for the transport specifier is The syntax for the transport specifier is
transport transport/profile/lower-transport.
/
profile
/
lower-transport
The default value for the "lower-transport" parameters is specific to The default value for the "lower-transport" parameters is specific to
the profile. For RTP/AVP, the default is UDP. the profile. For RTP/AVP, the default is UDP.
Below are the configuration parameters associated with transport: Below are the configuration parameters associated with transport:
General parameters: General parameters:
unicast | multicast: This parameter is a mutually exclusive unicast | multicast: This parameter is a mutually exclusive indica-
indication of whether unicast or multicast delivery will be tion of whether unicast or multicast delivery will be
attempted. One of the two values MUST be specified. Clients attempted. One of the two values MUST be specified. Clients
that are capable of handling both unicast and multicast that are capable of handling both unicast and multicast trans-
transmission MUST indicate such capability by including two mission MUST indicate such capability by including two full
full transport-specs with separate parameters for each. transport-specs with separate parameters for each.
destination: The address to which a stream will be sent. The destination: The address to which a stream will be sent. The |
client may specify the destination address with the client may specify the destination address with the destina- |
destination parameter. To avoid becoming the unwitting tion parameter. To avoid becoming the unwitting perpetrator of |
perpetrator of a remote-controlled denial-of-service a remote-controlled denial-of-service attack, a server SHOULD |
attack, a server SHOULD authenticate the client and SHOULD authenticate the client and SHOULD log such attempts before |
log such attempts before allowing the client to direct a allowing the client to direct a media stream to an address not |
media stream to an address not chosen by the server. This chosen by the server. This is particularly important if RTSP |
is particularly important if RTSP commands are issued via commands are issued via UDP, but implementations cannot rely |
UDP, but implementations cannot rely on TCP as reliable on TCP as reliable means of client identification by itself.
means of client identification by itself.
source: If the source address for the stream is different than source: If the source address for the stream is different than can
can be derived from the RTSP endpoint address (the server be derived from the RTSP endpoint address (the server in play-
in playback or the client in recording), the source address back or the client in recording), the source address MAY be
MAY be specified. specified.
This information may also be available through SDP. This information may also be available through SDP. How-
However, since this is more a feature of transport ever, since this is more a feature of transport than
than media initialization, the authoritative source media initialization, the authoritative source for this
for this information should be in the SETUP response. information should be in the SETUP response.
layers: The number of multicast layers to be used for this media layers: The number of multicast layers to be used for this media
stream. The layers are sent to consecutive addresses stream. The layers are sent to consecutive addresses starting
starting at the destination address. at the destination address.
mode: The mode parameter indicates the methods to be supported mode: The mode parameter indicates the methods to be supported for
for this session. Valid values are PLAY and RECORD. If not this session. Valid values are PLAY and RECORD. If not pro-
provided, the default is PLAY. vided, the default is PLAY.
append: If the mode parameter includes RECORD, the append append: If the mode parameter includes RECORD, the append parameter
parameter indicates that the media data should append to indicates that the media data should append to the existing
the existing resource rather than overwrite it. If resource rather than overwrite it. If appending is requested
appending is requested and the server does not support and the server does not support this, it MUST refuse the
this, it MUST refuse the request rather than overwrite the request rather than overwrite the resource identified by the
resource identified by the URI. The append parameter is URI. The append parameter is ignored if the mode parameter
ignored if the mode parameter does not contain RECORD. does not contain RECORD.
interleaved: The interleaved parameter implies mixing the media interleaved: The interleaved parameter implies mixing the media
stream with the control stream in whatever protocol is stream with the control stream in whatever protocol is being
being used by the control stream, using the mechanism used by the control stream, using the mechanism defined in
defined in Section 10.12. The argument provides the channel Section 10.13. The argument provides the channel number to be
number to be used in the $ statement. This parameter may be used in the $ statement. This parameter may be specified as a
specified as a range, e.g., interleaved=4-5 in cases where range, e.g., interleaved=4-5 in cases where the transport
the transport choice for the media stream requires it. choice for the media stream requires it.
This allows RTP/RTCP to be handled similarly to the This allows RTP/RTCP to be handled similarly to the way
way that it is done with UDP, i.e., one channel for that it is done with UDP, i.e., one channel for RTP and
RTP and the other for RTCP. the other for RTCP.
Multicast-specific: Multicast-specific:
ttl: multicast time-to-live. ttl: multicast time-to-live.
RTP-specific: RTP-specific:
port: This parameter provides the RTP/RTCP port pair for a port: This parameter provides the RTP/RTCP port pair for a multi-
multicast session. It is specified as a range, e.g., cast session. It is specified as a range, e.g., port=3456-3457
port=3456-3457
client_port: This parameter provides the unicast RTP/RTCP port client_port: This parameter provides the unicast RTP/RTCP port pair
pair on the client where media data and control information on the client where media data and control information is to
is to be sent. It is specified as a range, e.g., be sent. It is specified as a range, e.g., port=3456-3457
port=3456-3457 server_port: This parameter provides the unicast RTP/RTCP port pair
server_port: This parameter provides the unicast RTP/RTCP port on the server where media data and control information is to
pair on the server where media data and control information be sent. It is specified as a range, e.g., port=3456-3457
is to be sent. It is specified as a range, e.g.,
port=3456-3457
ssrc: The ssrc parameter indicates the RTP SSRC [27] value that ssrc: The ssrc parameter indicates the RTP SSRC [23] value that
should be (request) or will be (response) used by the media should be (request) or will be (response) used by the media
server. This parameter is only valid for unicast server. This parameter is only valid for unicast transmission.
transmission. It identifies the synchronization source to It identifies the synchronization source to be associated with
be associated with the media stream, and is expressed as an the media stream, and is expressed as an eight digit hexideci-
eight digit hexidecimal value. mal value.
Transport ______________________________________________ "Transport" ":" 1#transport-spec Transport = "Transport" ":" 1#transport-spec
transport-spec = transport-id *parameter transport-spec = transport-id *parameter
transport-id = transport-protocol "/" profile ["/" lower-transport] transport-id = transport-protocol "/" profile ["/" lower-transport]
; no LWS is allowed inside transport-id ; no LWS is allowed inside transport-id
transport-protocol = "RTP" | token transport-protocol = "RTP" | token
profile = "AVP" | token profile = "AVP" | token
lower-transport = "TCP" | "UDP" | token lower-transport = "TCP" | "UDP" | token
parameter = ";" ( "unicast" | "multicast" ) parameter = ";" ( "unicast" | "multicast" )
| ";" "source" [ "=" address ] | ";" "source" [ "=" address ]
| ";" "destination" [ "=" address ] | ";" "destination" [ "=" address ]
| ";" "interleaved" "=" channel [ "-" channel ] | ";" "interleaved" "=" channel [ "-" channel ]
skipping to change at page 1, line 2737 skipping to change at page 1, line 2880
S->C: RTSP/1.0 200 OK S->C: RTSP/1.0 200 OK
CSeq: 302 CSeq: 302
Date: 23 Jan 1997 15:35:06 GMT Date: 23 Jan 1997 15:35:06 GMT
Session: 47112344 Session: 47112344
Transport: RTP/AVP;unicast;client_port=3456-3457; Transport: RTP/AVP;unicast;client_port=3456-3457;
server_port=6256-6257;mode="PLAY" server_port=6256-6257;mode="PLAY"
12.41 Unsupported 12.41 Unsupported
The Unsupported response-header field lists the features not The Unsupported response-header field lists the features not sup-
supported by the server. In the case where the feature was specified ported by the server. In the case where the feature was specified via
via the Proxy-Require field (Section 12.33), if there is a proxy on the Proxy-Require field (Section 12.32), if there is a proxy on the
the path between the client and the server, the proxy MUST insert a path between the client and the server, the proxy MUST insert a
response message with a status code of 551 (Option Not Supported). response message with a status code of 551 (Option Not Supported).
See Section 12.33 for a usage example. See Section 12.32 for a usage example.
Unsupported _ "Unsupported" ":" 1#option-tag Unsupported = "Unsupported" ":" 1#option-tag
12.42 User-Agent 12.42 User-Agent
See [H14.42] See [H14.43]
12.43 Vary 12.43 Vary
See [H14.43] See [H14.44]
12.44 Via 12.44 Via
See [H14.44]. See [H14.45].
12.45 WWW-Authenticate 12.45 WWW-Authenticate
See [H14.46]. See [H14.47].
13 Caching 13 Caching
In HTTP, response-request pairs are cached. RTSP differs In HTTP, response-request pairs are cached. RTSP differs signifi-
significantly in that respect. Responses are not cacheable, with the cantly in that respect. Responses are not cacheable, with the excep-
exception of the presentation description returned by DESCRIBE or tion of the presentation description returned by DESCRIBE or included
included with ANNOUNCE. (Since the responses for anything but with ANNOUNCE. (Since the responses for anything but DESCRIBE and
DESCRIBE and GET_PARAMETER do not return any data, caching is not GET_PARAMETER do not return any data, caching is not really an issue
really an issue for these requests.) However, it is desirable for the for these requests.) However, it is desirable for the continuous
continuous media data, typically delivered out-of-band with respect media data, typically delivered out-of-band with respect to RTSP, to
to RTSP, to be cached, as well as the session description. be cached, as well as the session description.
On receiving a SETUP or PLAY request, a proxy ascertains whether it On receiving a SETUP or PLAY request, a proxy ascertains whether it
has an up-to-date copy of the continuous media content and its has an up-to-date copy of the continuous media content and its
description. It can determine whether the copy is up-to-date by description. It can determine whether the copy is up-to-date by issu-
issuing a SETUP or DESCRIBE request, respectively, and comparing ing a SETUP or DESCRIBE request, respectively, and comparing the
the Last-Modified header with that of the cached copy. If the copy Last-Modified header with that of the cached copy. If the copy is not
is not up-to-date, it modifies the SETUP transport parameters as up-to-date, it modifies the SETUP transport parameters as appropriate
appropriate and forwards the request to the origin server. Subsequent and forwards the request to the origin server. Subsequent control
control commands such as PLAY or PAUSE then pass the proxy commands such as PLAY or PAUSE then pass the proxy unmodified. The
unmodified. The proxy delivers the continuous media data to the proxy delivers the continuous media data to the client, while possi-
client, while possibly making a local copy for later reuse. The exact bly making a local copy for later reuse. The exact behavior allowed
behavior allowed to the cache is given by the cache-response to the cache is given by the cache-response directives described in
directives described in Section 12.9. A cache MUST answer any Section 12.9. A cache MUST answer any DESCRIBE requests if it is cur-
DESCRIBE requests if it is currently serving the stream to the rently serving the stream to the requestor, as it is possible that
requestor, as it is possible that low-level details of the stream low-level details of the stream description may have changed on the
description may have changed on the origin-server. origin-server.
Note that an RTSP cache, unlike the HTTP cache, is of the "cut- Note that an RTSP cache, unlike the HTTP cache, is of the "cut-
through" variety. Rather than retrieving the whole resource from the through" variety. Rather than retrieving the whole resource from the
origin server, the cache simply copies the streaming data as it origin server, the cache simply copies the streaming data as it
passes by on its way to the client. Thus, it does not introduce passes by on its way to the client. Thus, it does not introduce addi-
additional latency. tional latency.
To the client, an RTSP proxy cache appears like a regular media To the client, an RTSP proxy cache appears like a regular media
server, to the media origin server like a client. Just as an HTTP server, to the media origin server like a client. Just as an HTTP
cache has to store the content type, content language, and so on for 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 the objects it caches, a media cache has to store the presentation
description. Typically, a cache eliminates all transport-references description. Typically, a cache eliminates all transport-references
(that is, multicast information) from the presentation description, (that is, multicast information) from the presentation description,
since these are independent of the data delivery from the cache to since these are independent of the data delivery from the cache to
the client. Information on the encodings remains the same. If the the client. Information on the encodings remains the same. If the
cache is able to translate the cached media data, it would create a cache is able to translate the cached media data, it would create a
skipping to change at page 1, line 2817 skipping to change at page 1, line 2960
14 Examples 14 Examples
The following examples refer to stream description formats that are The following examples refer to stream description formats that are
not standards, such as RTSL. The following examples are not to be not standards, such as RTSL. The following examples are not to be
used as a reference for those formats. used as a reference for those formats.
14.1 Media on Demand (Unicast) 14.1 Media on Demand (Unicast)
Client C requests a movie from media servers A ( audio.example.com ) Client C requests a movie from media servers A ( audio.example.com )
and V ( video.example.com ). The media description is stored on a web and V ( video.example.com ). The media description is stored on a web
server W. The media description contains descriptions of the server W. The media description contains descriptions of the presen-
presentation and all its streams, including the codecs that are tation and all its streams, including the codecs that are available,
available, dynamic RTP payload types, the protocol stack, and content dynamic RTP payload types, the protocol stack, and content informa-
information such as language or copyright restrictions. It may also tion such as language or copyright restrictions. It may also give an
give an indication about the timeline of the movie. indication about the timeline of the movie.
In this example, the client is only interested in the last part of In this example, the client is only interested in the last part of
the movie. the movie.
C->W: GET /twister.sdp HTTP/1.1 C->W: GET /twister.sdp HTTP/1.1
Host: www.example.com Host: www.example.com
Accept: application/sdp Accept: application/sdp
W->C: HTTP/1.0 200 OK W->C: HTTP/1.0 200 OK
Content-Type: application/sdp Content-Type: application/sdp
skipping to change at page 1, line 2906 skipping to change at page 1, line 3049
V->C: RTSP/1.0 200 OK V->C: RTSP/1.0 200 OK
CSeq: 3 CSeq: 3
Even though the audio and video track are on two different servers, Even though the audio and video track are on two different servers,
and may start at slightly different times and may drift with respect and may start at slightly different times and may drift with respect
to each other, the client can synchronize the two using standard RTP to each other, the client can synchronize the two using standard RTP
methods, in particular the time scale contained in the RTCP sender methods, in particular the time scale contained in the RTCP sender
reports. reports.
14.2 Streaming of a Container file 14.2 Streaming of a Container file
For purposes of this example, a container file is a storage entity in For purposes of this example, a container file is a storage entity in
which multiple continuous media types pertaining to the same end-user which multiple continuous media types pertaining to the same end-user
presentation are present. In effect, the container file represents an presentation are present. In effect, the container file represents an
RTSP presentation, with each of its components being RTSP streams. RTSP presentation, with each of its components being RTSP streams.
Container files are a widely used means to store such presentations. Container files are a widely used means to store such presentations.
While the components are transported as independent streams, it is While the components are transported as independent streams, it is
desirable to maintain a common context for those streams at the desirable to maintain a common context for those streams at the
server end. server end.
This enables the server to keep a single storage handle This enables the server to keep a single storage handle open
open easily. It also allows treating all the streams easily. It also allows treating all the streams equally in
equally in case of any prioritization of streams by the case of any prioritization of streams by the server.
server.
It is also possible that the presentation author may wish to prevent It is also possible that the presentation author may wish to prevent
selective retrieval of the streams by the client in order to preserve selective retrieval of the streams by the client in order to preserve
the artistic effect of the combined media presentation. Similarly, in the artistic effect of the combined media presentation. Similarly, in
such a tightly bound presentation, it is desirable to be able to such a tightly bound presentation, it is desirable to be able to con-
control all the streams via a single control message using an trol all the streams via a single control message using an aggregate
aggregate URL. URL.
The following is an example of using a single RTSP session to control The following is an example of using a single RTSP session to control
multiple streams. It also illustrates the use of aggregate URLs. multiple streams. It also illustrates the use of aggregate URLs.
Client C requests a presentation from media server M. The movie is Client C requests a presentation from media server M. The movie is
stored in a container file. The client has obtained an RTSP URL to stored in a container file. The client has obtained an RTSP URL to
the container file. the container file.
C->M: DESCRIBE rtsp://foo/twister RTSP/1.0 C->M: DESCRIBE rtsp://foo/twister RTSP/1.0
CSeq: 1 CSeq: 1
skipping to change at page 1, line 3020 skipping to change at page 1, line 3161
aggregate URL may not be used for SETUP and one control message is aggregate URL may not be used for SETUP and one control message is
required per stream to set up transport parameters. required per stream to set up transport parameters.
This keeps the syntax of the Transport header simple and This keeps the syntax of the Transport header simple and
allows easy parsing of transport information by firewalls. allows easy parsing of transport information by firewalls.
14.3 Single Stream Container Files 14.3 Single Stream Container Files
Some RTSP servers may treat all files as though they are "container Some RTSP servers may treat all files as though they are "container
files", yet other servers may not support such a concept. Because of files", yet other servers may not support such a concept. Because of
this, clients SHOULD use the rules set forth in the session this, clients SHOULD use the rules set forth in the session descrip-
description for request URLs, rather than assuming that a consistent tion for request URLs, rather than assuming that a consistent URL may
URL may always be used throughout. Here's an example of how a multi- always be used throughout. Here's an example of how a multi-stream
stream server might expect a single-stream file to be served: server might expect a single-stream file to be served:
C->S DESCRIBE rtsp://foo.com/test.wav RTSP/1.0 C->S DESCRIBE rtsp://foo.com/test.wav RTSP/1.0
Accept: application/x-rtsp-mh, application/sdp Accept: application/x-rtsp-mh, application/sdp
CSeq: 1 CSeq: 1
S->C RTSP/1.0 200 OK S->C RTSP/1.0 200 OK
CSeq: 1 CSeq: 1
Content-base: rtsp://foo.com/test.wav/ Content-base: rtsp://foo.com/test.wav/
Content-type: application/sdp Content-type: application/sdp
Content-length: 48 Content-length: 48
skipping to change at page 1, line 3064 skipping to change at page 1, line 3205
C->S PLAY rtsp://foo.com/test.wav RTSP/1.0 C->S PLAY rtsp://foo.com/test.wav RTSP/1.0
CSeq: 3 CSeq: 3
Session: 2034820394 Session: 2034820394
S->C RTSP/1.0 200 OK S->C RTSP/1.0 200 OK
CSeq: 3 CSeq: 3
Session: 2034820394 Session: 2034820394
RTP-Info: url=rtsp://foo.com/test.wav/streamid=0; RTP-Info: url=rtsp://foo.com/test.wav/streamid=0;
seq=981888;rtptime=3781123 seq=981888;rtptime=3781123
Note the different URL in the SETUP command, and then the switch Note the different URL in the SETUP command, and then the switch back
back to the aggregate URL in the PLAY command. This makes complete to the aggregate URL in the PLAY command. This makes complete sense
sense when there are multiple streams with aggregate control, but is when there are multiple streams with aggregate control, but is less
less than intuitive in the special case where the number of streams than intuitive in the special case where the number of streams is
is one. one.
In this special case, it is recommended that servers be forgiving of In this special case, it is recommended that servers be forgiving of
implementations that send: implementations that send:
C->S PLAY rtsp://foo.com/test.wav/streamid=0 RTSP/1.0 C->S PLAY rtsp://foo.com/test.wav/streamid=0 RTSP/1.0
CSeq: 3 CSeq: 3
In the worst case, servers should send back: In the worst case, servers should send back:
S->C RTSP/1.0 460 Only aggregate operation allowed S->C RTSP/1.0 460 Only aggregate operation allowed
skipping to change at page 1, line 3140 skipping to change at page 1, line 3281
Session: 0456804596 Session: 0456804596
C->M: PLAY rtsp://live.example.com/concert/audio RTSP/1.0 C->M: PLAY rtsp://live.example.com/concert/audio RTSP/1.0
CSeq: 3 CSeq: 3
Session: 0456804596 Session: 0456804596
M->C: RTSP/1.0 200 OK M->C: RTSP/1.0 200 OK
CSeq: 3 CSeq: 3
Session: 0456804596 Session: 0456804596
14.5 Playing media into an existing session 14.5 Recording
A conference participant C wants to have the media server M play back
a demo tape into an existing conference. C indicates to the media
server that the network addresses and encryption keys are already
given by the conference, so they should not be chosen by the server.
The example omits the simple ACK responses.
C->M: DESCRIBE rtsp://server.example.com/demo/548/sound RTSP/1.0
CSeq: 1
Accept: application/sdp
M->C: RTSP/1.0 200 1 OK
Content-type: application/sdp
Content-Length: 44
v=0
o=- 2890844526 2890842807 IN IP4 192.16.24.202
s=RTSP Session
i=See above
t=0 0
m=audio 0 RTP/AVP 0
C->M: SETUP rtsp://server.example.com/demo/548/sound RTSP/1.0
CSeq: 2
Transport: RTP/AVP;multicast;destination=225.219.201.15;
port=7000-7001;ttl=127
Conference: 199702170042.SAA08642@obiwan.arl.wustl.edu%20Starr
M->C: RTSP/1.0 200 OK
CSeq: 2
Transport: RTP/AVP;multicast;destination=225.219.201.15;
port=7000-7001;ttl=127
Session: 91389234234
Conference: 199702170042.SAA08642@obiwan.arl.wustl.edu%20Starr
C->M: PLAY rtsp://server.example.com/demo/548/sound RTSP/1.0
CSeq: 3
Session: 91389234234
M->C: RTSP/1.0 200 OK
CSeq: 3
14.6 Recording
The conference participant client C asks the media server M to record The conference participant client C asks the media server M to record
the audio and video portions of a meeting. The client uses the the audio and video portions of a meeting. The client uses the
ANNOUNCE method to provide meta-information about the recorded ANNOUNCE method to provide meta-information about the recorded ses-
session to the server. sion to the server.
C->M: ANNOUNCE rtsp://server.example.com/meeting RTSP/1.0 C->M: ANNOUNCE rtsp://server.example.com/meeting RTSP/1.0
CSeq: 90 CSeq: 90
Content-Type: application/sdp Content-Type: application/sdp
Content-Length: 121 Content-Length: 121
v=0 v=0
o=camera1 3080117314 3080118787 IN IP4 195.27.192.36 o=camera1 3080117314 3080118787 IN IP4 195.27.192.36
s=IETF Meeting, Munich - 1 s=IETF Meeting, Munich - 1
i=The thirty-ninth IETF meeting will be held in Munich, Germany i=The thirty-ninth IETF meeting will be held in Munich, Germany
skipping to change at page 1, line 3252 skipping to change at page 1, line 3350
M->C: RTSP/1.0 200 OK M->C: RTSP/1.0 200 OK
CSeq: 93 CSeq: 93
15 Syntax 15 Syntax
The RTSP syntax is described in an augmented Backus-Naur form (BNF) The RTSP syntax is described in an augmented Backus-Naur form (BNF)
as used in RFC 2068 [2]. as used in RFC 2068 [2].
15.1 Base Syntax 15.1 Base Syntax
OCTET ____________________________ <any 8-bit sequence of data> OCTET = <any 8-bit sequence of data>
CHAR ____________________________ <any US-ASCII character (octets 0 - 127)> CHAR = <any US-ASCII character (octets 0 - 127)>
UPALPHA ____________________________ <any US-ASCII uppercase letter "A".."Z"> UPALPHA = <any US-ASCII uppercase letter "A".."Z">
LOALPHA ____________________________ <any US-ASCII lowercase letter "a".."z"> LOALPHA = <any US-ASCII lowercase letter "a".."z">
ALPHA ____________________________ UPALPHA | LOALPHA ALPHA = UPALPHA | LOALPHA
DIGIT ____________________________ <any US-ASCII digit "0".."9"> DIGIT = <any US-ASCII digit "0".."9">
CTL ____________________________ <any US-ASCII control character CTL = <any US-ASCII control character
(octets 0 - 31) and DEL (127)> (octets 0 - 31) and DEL (127)>
CR ____________________________ <US-ASCII CR, carriage return (13)> CR = <US-ASCII CR, carriage return (13)>
LF ____________________________ <US-ASCII LF, linefeed (10)> LF = <US-ASCII LF, linefeed (10)>
SP ____________________________ <US-ASCII SP, space (32)> SP = <US-ASCII SP, space (32)>
HT ____________________________ <US-ASCII HT, horizontal-tab (9)> HT = <US-ASCII HT, horizontal-tab (9)>
<"> ____________________________ <US-ASCII double-quote mark (34)> <"> = <US-ASCII double-quote mark (34)>
CRLF ____________________________ CR LF BACKSLASH = <US-ASCII backslash (92)>
LWS ____________________________ [CRLF] 1*( SP | HT ) CRLF = CR LF
TEXT ____________________________ <any OCTET except CTLs> LWS = [CRLF] 1*( SP | HT )
tspecials ____________________________ "(" | ")" | "<" | ">" | "@" TEXT = <any OCTET except CTLs>
| "," | ";" | ":" | " tspecials = "(" | ")" | "<" | ">" | "@"
\&\h'|\n(40u'\h'|\n(41u'\h'|\n(42u' | "," | ";" | ":" | BACKSLASH | <">
" | <">
| "/" | "[" | "]" | "?" | "=" | "/" | "[" | "]" | "?" | "="
| "{" | "}" | SP | HT | "{" | "}" | SP | HT
token ____________________________ 1*<any CHAR except CTLs or tspecials> token = 1*<any CHAR except CTLs or tspecials>
quoted-string ____________________________ ( <"> *(qdtext) <"> ) quoted-string = ( <"> *(qdtext) <"> )
qdtext ____________________________ <any TEXT except <">> qdtext = <any TEXT except <">>
quoted-pair ____________________________ " quoted-pair = BACKSLASH CHAR
\&\h'|\n(40u'\h'|\n(41u'\h'|\n(42u' message-header = field-name ":" [ field-value ] CRLF
" CHAR field-name = token
message-header ____________________________ field-name ":" [ field-value ] CRLF field-value = *( field-content | LWS )
field-name ____________________________ token field-content = <the OCTETs making up the field-value and
field-value ____________________________ *( field-content | LWS )
field-content ____________________________ <the OCTETs making up the field-value and
consisting consisting
of either *TEXT or combinations of token, tspecials, of either *TEXT or combinations of token, tspecials,
and quoted-string> and quoted-string>
safe ____________________________ "$" | "-" | "_" | "." | "+" safe = "$" | "-" | "_" | "." | "+"
extra ____________________________ "!" | "*" | "'" | "(" | ")" | "," extra = "!" | "*" | "'" | "(" | ")" | ","
hex ____________________________ DIGIT | "A" | "B" | "C" | "D" | "E" | "F" | hex = DIGIT | "A" | "B" | "C" | "D" | "E" | "F" |
"a" | "b" | "c" | "d" | "e" | "f" "a" | "b" | "c" | "d" | "e" | "f"
escape ____________________________ "%" hex hex escape = "%" hex hex
reserved ____________________________ ";" | "/" | "?" | ":" | "@" | "&" | "=" reserved = ";" | "/" | "?" | ":" | "@" | "&" | "="
unreserved ____________________________ alpha | digit | safe | extra unreserved = alpha | digit | safe | extra
xchar ____________________________ unreserved | reserved | escape xchar = unreserved | reserved | escape
16 Security Considerations 16 Security Considerations
Because of the similarity in syntax and usage between RTSP servers Because of the similarity in syntax and usage between RTSP servers
and HTTP servers, the security considerations outlined in [H15] and HTTP servers, the security considerations outlined in [H15]
apply. Specifically, please note the following: apply. Specifically, please note the following:
Authentication Mechanisms: RTSP and HTTP share common Authentication Mechanisms: RTSP and HTTP share common authentica-
authentication schemes, and thus should follow the same tion schemes, and thus should follow the same prescriptions
prescriptions with regards to authentication. See [H15.1] with regards to authentication. See chapter 15.1 of [2] for
for client authentication issues, and [H15.2] for issues client authentication issues, and chapter 15.2 of [2] for
regarding support for multiple authentication mechanisms. issues regarding support for multiple authentication mecha-
nisms.
Abuse of Server Log Information: RTSP and HTTP servers will Abuse of Server Log Information: RTSP and HTTP servers will presum-
presumably have similar logging mechanisms, and thus should ably have similar logging mechanisms, and thus should be
be equally guarded in protecting the contents of those equally guarded in protecting the contents of those logs, thus
logs, thus protecting the privacy of the users of the protecting the privacy of the users of the servers. See
servers. See [H15.3] for HTTP server recommendations [H15.1.1] for HTTP server recommendations regarding server
regarding server logs. logs.
Transfer of Sensitive Information: There is no reason to believe Transfer of Sensitive Information: There is no reason to believe
that information transferred via RTSP may be any less that information transferred via RTSP may be any less sensi-
sensitive than that normally transmitted via HTTP. tive than that normally transmitted via HTTP. Therefore, all
Therefore, all of the precautions regarding the protection of the precautions regarding the protection of data privacy
of data privacy and user privacy apply to implementors of and user privacy apply to implementors of RTSP clients,
RTSP clients, servers, and proxies. See [H15.4] for further servers, and proxies. See [H15.1.2] for further details.
details.
Attacks Based On File and Path Names: Though RTSP URLs are Attacks Based On File and Path Names: Though RTSP URLs are opaque
opaque handles that do not necessarily have file system handles that do not necessarily have file system semantics, it
semantics, it is anticipated that many implementations will is anticipated that many implementations will translate por-
translate portions of the request URLs directly to file tions of the request URLs directly to file system calls. In
system calls. In such cases, file systems SHOULD follow the such cases, file systems SHOULD follow the precautions out-
precautions outlined in [H15.5], such as checking for ".." lined in [H15.5], such as checking for ".." in path compo-
in path components. nents.
Personal Information: RTSP clients are often privy to the same Personal Information: RTSP clients are often privy to the same
information that HTTP clients are (user name, location, information that HTTP clients are (user name, location, etc.)
etc.) and thus should be equally. See [H15.6] for further and thus should be equally. See [H15.1] for further recommen-
recommendations. dations.
Privacy Issues Connected to Accept Headers: Since may of the Privacy Issues Connected to Accept Headers: Since may of the same
same "Accept" headers exist in RTSP as in HTTP, the same "Accept" headers exist in RTSP as in HTTP, the same caveats
caveats outlined in [H15.7] with regards to their use outlined in [H15.1.4] with regards to their use should be fol-
should be followed. lowed.
DNS Spoofing: Presumably, given the longer connection times DNS Spoofing: Presumably, given the longer connection times typi-
typically associated to RTSP sessions relative to HTTP cally associated to RTSP sessions relative to HTTP sessions,
sessions, RTSP client DNS optimizations should be less RTSP client DNS optimizations should be less prevalent.
prevalent. Nonetheless, the recommendations provided in Nonetheless, the recommendations provided in [H15.3] are still
[H15.8] are still relevant to any implementation which relevant to any implementation which attempts to rely on a
attempts to rely on a DNS-to-IP mapping to hold beyond a DNS-to-IP mapping to hold beyond a single use of the mapping.
single use of the mapping.
Location Headers and Spoofing: If a single server supports Location Headers and Spoofing: If a single server supports multiple
multiple organizations that do not trust one another, then organizations that do not trust one another, then it must
it must check the values of Location and Content-Location check the values of Location and Content-Location header
header fields in responses that are generated under control fields in responses that are generated under control of said
of said organizations to make sure that they do not attempt organizations to make sure that they do not attempt to invali-
to invalidate resources over which they have no authority. date resources over which they have no authority. ([H15.4])
([H15.9])
In addition to the recommendations in the current HTTP specification In addition to the recommendations in the current HTTP specification
(RFC 2068 [2], as of this writing), future HTTP specifications may (RFC 2616 [26], as of this writing) and also of the previous RFC2068
provide additional guidance on security issues. [2], future HTTP specifications may provide additional guidance on
security issues.
The following are added considerations for RTSP implementations. The following are added considerations for RTSP implementations.
Concentrated denial-of-service attack: The protocol offers the Concentrated denial-of-service attack: The protocol offers the
opportunity for a remote-controlled denial-of-service opportunity for a remote-controlled denial-of-service attack.
attack.
The attacker may initiate traffic flows to one or more IP The attacker may initiate traffic flows to one or more IP
addresses by specifying them as the destination in SETUP addresses by specifying them as the destination in SETUP
requests. While the attacker's IP address may be known in requests. While the attacker's IP address may be known in this
this case, this is not always useful in prevention of more case, this is not always useful in prevention of more attacks
attacks or ascertaining the attackers identity. Thus, an or ascertaining the attackers identity. Thus, an RTSP server
RTSP server SHOULD only allow client-specified destinations SHOULD only allow client-specified destinations for RTSP-ini-
for RTSP-initiated traffic flows if the server has verified tiated traffic flows if the server has verified the client's
the client's identity, either against a database of known identity, either against a database of known users using RTSP
users using RTSP authentication mechanisms (preferably authentication mechanisms (preferably digest authentication or
digest authentication or stronger), or other secure means. stronger), or other secure means.
Session hijacking: Since there is no relation between a Session hijacking: Since there is no relation between a transport
transport layer connection and an RTSP session, it is layer connection and an RTSP session, it is possible for a
possible for a malicious client to issue requests with malicious client to issue requests with random session identi-
random session identifiers which would affect unsuspecting fiers which would affect unsuspecting clients. The server
clients. The server SHOULD use a large, random and non- SHOULD use a large, random and non-sequential session identi-
sequential session identifier to minimize the possibility fier to minimize the possibility of this kind of attack.
of this kind of attack.
Authentication: Servers SHOULD implement both basic and digest Authentication: Servers SHOULD implement both basic and digest [6]
[8] authentication. In environments requiring tighter authentication. In environments requiring tighter security for
security for the control messages, transport layer the control messages, transport layer mechanisms such as TLS
mechanisms such as TLS (RFC 2246 [7]) SHOULD be used. (RFC 2246 [27]) SHOULD be used.
Stream issues: RTSP only provides for stream control. Stream Stream issues: RTSP only provides for stream control. Stream deliv-
delivery issues are not covered in this section, nor in the ery issues are not covered in this section, nor in the rest of
rest of this draft. RTSP implementations will most likely this draft. RTSP implementations will most likely rely on
rely on other protocols such as RTP, IP multicast, RSVP and other protocols such as RTP, IP multicast, RSVP and IGMP, and
IGMP, and should address security considerations brought up should address security considerations brought up in those and
in those and other applicable specifications. other applicable specifications.
Persistently suspicious behavior: RTSP servers SHOULD return Persistently suspicious behavior: RTSP servers SHOULD return error
error code 403 (Forbidden) upon receiving a single instance code 403 (Forbidden) upon receiving a single instance of
of behavior which is deemed a security risk. RTSP servers behavior which is deemed a security risk. RTSP servers SHOULD
SHOULD also be aware of attempts to probe the server for also be aware of attempts to probe the server for weaknesses
weaknesses and entry points and MAY arbitrarily disconnect and entry points and MAY arbitrarily disconnect and ignore
and ignore further requests clients which are deemed to be further requests clients which are deemed to be in violation
in violation of local security policy. of local security policy.
A RTSP Protocol State Machines 17 IANA Considerations
This section set up a number of registers for RTSP that should be
maintained by IANA. For each registry there is a description on what
it shall contain, what specification is needed when adding a entry
with IANA, and finally the entries that this document needs to regis-
ter. See also the section 1.5 "Extending RTSP".
The RTSP client and server state machines describe the behavior of The sections describing how to register an item uses some of the
the protocol from RTSP session initialization through RTSP session requirements level described in RFC 2434 [29], namely " First Come,
termination. First Served", "Specification Required", and "Standards Action".
State is defined on a per object basis. An object is uniquely A registration request to IANA MUST contain the following informa-
identified by the stream URL and the RTSP session identifier. Any tion:
request/reply using aggregate URLs denoting RTSP presentations
composed of multiple streams will have an effect on the individual
states of all the streams. For example, if the presentation /movie
contains two streams, /movie/audio and /movie/video , then the
following command:
PLAY rtsp://foo.com/movie RTSP/1.0 + A name of the item to register according to the rules specified
CSeq: 559 by the intended registry.
Session: 12345678
will have an effect on the states of movie/audio and movie/video + 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);
This example does not imply a standard way to represent + A reference to a further description, if available, for example
streams in URLs or a relation to the filesystem. See (in order of preference) an RFC, a published paper, a patent fil-
Section 3.2. ing, a technical report, documented source code or a computer
manual;
The requests OPTIONS, ANNOUNCE, DESCRIBE, GET_PARAMETER, + For proprietary options, contact information (postal and email
SET_PARAMETER do not have any effect on client or server state and address);
are therefore not listed in the state tables.
A.1 Client State Machine 17.1 Option-tags
The client can assume the following states: 17.1.1 Description
Init : SETUP has been sent, waiting for reply. When a client and server try to determine what part and functionality
of the RTSP specification and any future extensions that its counter
part implements there is need for a namespace. This registry con-
tains named entries representing certain functionality.
Ready : SETUP reply received or PAUSE reply received while in The usage of option-tags is explained in section 3.7 and 10.1.
Playing state.
Playing : PLAY reply received 17.1.2 Registering New Option Tags with IANA
Recording : RECORD reply received The registering of option tags is done on a first come, first served
basis.
In general, the client changes state on receipt of replies to The name of the option MUST follow these rules: The name may be of
requests. Note that some requests are effective at a future time or any length, but SHOULD be no more than twenty characters long. The
position (such as a PAUSE), and state also changes accordingly. If name MUST not contain any spaces, control characters or periods. Any
no explicit SETUP is required for the object (for example, it is proprietary option SHOULD have as the first part of the name a vendor
available via a multicast group), state begins at Ready are only two tag, which identifies the company/person.
states, Ready and Playing The client also changes state from
Playing/Recording to Ready when the end of the requested range is
reached.
The "next state" column indicates the state assumed after receiving a 17.1.3 Registered entries
success response (2xx). If a request yields a status code of 3xx, the
state becomes Init , and a status code of 4xx yields no change in
state. Messages not listed for each state MUST NOT be issued by the
client in that state, with the exception of messages not affecting
state, as listed above. Receiving a REDIRECT from the server is
equivalent to receiving a 3xx redirect status from the server.
state message sent next state after response The following options tags are in this specification defined and
____________________________________________________________ hereby registered. The change control belongs to the Authors and the
Init SETUP IETF MMUSIC WG.
Ready
TEARDOWN
Init
Ready PLAY
Playing
RECORD
Recording
TEARDOWN
Init
SETUP
Ready
Playing PAUSE
Ready
TEARDOWN
Init
PLAY
Playing
SETUP
Playing
(changed transport)
Recording PAUSE
Ready
TEARDOWN
Init
RECORD
Recording
SETUP
Recording
(changed transport)
A.2 Server State Machine play-basic: The minimal implementation for playback operations
according to section D.
The server can assume the following states: record-basic: The minimal implementation for record operations
according to section D.
Init : The initial state, no valid SETUP has been received yet. play-setup: The use of teardown and setup in play state.
Ready : Last SETUP received was successful, reply sent or after record-setup: The use of setup and teardown in record state.
playing, last PAUSE received was successful, reply sent.
Playing : Last PLAY received was successful, reply sent. Data 17.2 RTSP Methods
is being sent.
Recording : The server is recording media data. 17.2.1 Description
In general, the server changes state on receiving requests. If the What a method is, is described in section 10. Extending the protocol
server is in state Playing or Recording and in unicast mode, it MAY with new methods allow for totally new functionality.
revert to Init and tear down the RTSP session if it has not received
"wellness" information, such as RTCP reports or RTSP commands, from
the client for a defined interval, with a default of one minute. The
server can declare another timeout value in the Session response
header (Section 12.38). If the server is in state Ready , it MAY
revert to Init if it does not receive an RTSP request for an interval
of more than one minute. Note that some requests (such as PAUSE) may
be effective at a future time or position, and server state changes
at the appropriate time. The server reverts from state Playing or
Recording to state Ready at the end of the range requested by the
client.
The REDIRECT message, when sent, is effective immediately unless it 17.2.2 Registering New Methods with IANA
has a Range header specifying when the redirect is effective. In
such a case, server state will also change at the appropriate time.
If no explicit SETUP is required for the object, the state starts at A new method can only be registered through an IETF standards action.
Ready and there are only two states, Ready and Playing The reason is that new methods may radically change the protocols
behavior and purpose.
The "next state" column indicates the state assumed after sending a A specification for a new RTSP method MUST consist of the following
success response (2xx). If a request results in a status code of 3xx, items:
the state becomes Init change.
state message received next state + A method name which follows the BNF rules for methods.
_______________________________________
Init + A clear specification on what action and response a request with
SETUP the method will result in. Which directions the method is used,
Ready C->S or S->C or both. How the use of headers, if any, modifies
TEARDOWN the behavior and effect of the method.
Init
Ready + A list or table specifying which of the registered headers that
PLAY are allowed to use with the method in request or/and response.
Playing
SETUP + Describe how the method relates to network proxies.
Ready
TEARDOWN 17.2.3 Registered entries
Init This specification, RFCXXXX, registers 12 methods: DESCRIBE,
RECORD ANNOUNCE, GET_PARAMETER, OPTIONS, PAUSE, PING, PLAY, RECORD, REDI-
Recording RECT, SETUP, SET_PARAMETER, and TEARDOWN.
Playing
PLAY 17.3 RTSP Headers
Playing
PAUSE 17.3.1 Description
Ready
TEARDOWN By specifying new headers a method(s) can be enhanced in many differ-
Init ent ways. An unknown header will be ignored by the receiving entity.
SETUP If the new header is vital for a certain functionality, a option tag
Playing for the functionality can be created and demanded to be used by the
Recording counter-part with the inclusion of a Require header carrying the
RECORD option tag.
Recording
PAUSE Unregistered headers SHALL have a name starting with "X-" to signal
Ready that it is a experimental header.
TEARDOWN
Init 17.3.2 Registering New Headers with IANA
SETUP
Recording A specification is required to register a header.
The specification MUST contain the following information:
+ The header name following the BNF definition.
+ A BNF specification of how information (if any) is carried in the
header.
+ A list or table specifying when the header may be used, encom-
passing all methods, their request or response, the direction
(C->S or S->C).
+ How the header shall be handled by proxies.
+ A description of the purpose of the header.
17.3.3 Registered entries
All headers specified in section 12 in RFC XXXX are to be registered.
17.4 Parameters
17.4.1 Description
A Parameter allow the counterpart to set something 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:
+ The parameter name is a BNF token. The name SHOULD not be more
than 20 characters long. Any proprietary parameter should start
the name with a vendor tag, as clearly as possible identify the
company or person.
+ Any non proprietary parameter MUST in the form of BNF specify
what value types that are associated with the parameter.
17.4.3 Registered entries
For the moment no known parameters are defined in RFC XXXX.
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
variable is not mandated.
A.3 Abbreviations
To make the state tables more compact a number of abbreviations are
used, which are explained below.
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 result in ending of the session.
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.
ANNOUNCE S->C, Update SES descr.
Table 5: None state-machine changing events
The methods in Table 5 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 can only be left
by processing a correct SETUP request. As seen in the table the two
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 Set RedP
S->C:REDIRECT no range hdr Init Stop Media Playout
RedP reached Init
Table 7: State: Ready-nm
The Ready-nm state has no media streams and therefore can't play or
record. This state exist so that all session related parameters and
resources can be kept while changing media stream(s). As seen in
Table 7 the operations are limited to setting up a new media or tear-
ing down the session. The established session can also be redirected
with the REDIRECT method.
In the Ready state, see Table 8, some of the actions are depending on
the number of media streams in the session, i.e. aggregated or 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 the session will remain and a session header
MUST be returned in the response. The number of media streams remain-
ing after tearing down a media stream determines the new state.
The Play state table, see Table 9, is the largest. The table contains
an number of request that has presentation URL as a prerequisite on
the request URL, this is due to 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 Ready-nm 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 Record
S->C:REDIRECT Range hdr Ready Set RedP
S->C:REDIRECT no range hdr Init
Timeout Init
RedP reached Init
Table 8: 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 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, 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 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
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 Ready
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
Timeout Init
Table 10: State: Record
The Record state Table 10 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 B Interaction with RTP
RTSP allows media clients to control selected, non-contiguous RTSP allows media clients to control selected, non-contiguous sec-
sections of media presentations, rendering those streams with an RTP tions of media presentations, rendering those streams with an RTP
media layer[27]. The media layer rendering the RTP stream should not 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 be affected by jumps in NPT. Thus, both RTP sequence numbers and RTP
timestamps MUST be continuous and monotonic across jumps of NPT. timestamps MUST be continuous and monotonic across jumps of NPT.
As an example, assume a clock frequency of 8000 Hz, a packetization As an example, assume a clock frequency of 8000 Hz, a packetization
interval of 100 ms and an initial sequence number and timestamp of 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 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 18 through 20. The first segment is presented as RTP packets with
sequence numbers 0 through 49 and timestamp 0 through 39,200. The sequence numbers 0 through 49 and timestamp 0 through 39,200. The
second segment consists of RTP packets with sequence number 50 second segment consists of RTP packets with sequence number 50
through 69, with timestamps 40,000 through 55,200. through 69, with timestamps 40,000 through 55,200.
We cannot assume that the RTSP client can communicate with We cannot assume that the RTSP client can communicate with the
the RTP media agent, as the two may be independent RTP media agent, as the two may be independent processes. If
processes. If the RTP timestamp shows the same gap as the the RTP timestamp shows the same gap as the NPT, the media
NPT, the media agent will assume that there is a pause in agent will assume that there is a pause in the presentation.
the presentation. If the jump in NPT is large enough, the If the jump in NPT is large enough, the RTP timestamp may roll
RTP timestamp may roll over and the media agent may believe over and the media agent may believe later packets to be
later packets to be duplicates of packets just played out. duplicates of packets just played out.
For certain datatypes, tight integration between the RTSP layer and For certain datatypes, tight integration between the RTSP layer and
the RTP layer will be necessary. This by no means precludes the above the RTP layer will be necessary. This by no means precludes the above
restriction. Combined RTSP/RTP media clients should use the RTP-Info restriction. Combined RTSP/RTP media clients should use the RTP-Info
field to determine whether incoming RTP packets were sent before or field to determine whether incoming RTP packets were sent before or
after a seek. after a seek.
For continuous audio, the server SHOULD set the RTP marker bit at the 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 beginning of serving a new PLAY request. This allows the client to
perform playout delay adaptation. perform playout delay adaptation.
For scaling (see Section 12.35), RTP timestamps should correspond to For scaling (see Section 12.34), RTP timestamps should correspond to
the playback timing. For example, when playing video recorded at 30 the playback timing. For example, when playing video recorded at 30
frames/second at a scale of two and speed (Section 12.36) of one, the 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 server would drop every second frame to maintain and deliver video
packets with the normal timestamp spacing of 3,000 per frame, but NPT packets with the normal timestamp spacing of 3,000 per frame, but NPT
would increase by 1/15 second for each video frame. would increase by 1/15 second for each video frame.
The client can maintain a correct display of NPT by noting the RTP The client can maintain a correct display of NPT by noting the RTP
timestamp value of the first packet arriving after repositioning. The timestamp value of the first packet arriving after repositioning. The
sequence parameter of the RTP-Info (Section 12.34) header provides sequence parameter of the RTP-Info (Section 12.33) header provides
the first sequence number of the next segment. the first sequence number of the next segment.
C Use of SDP for RTSP Session Descriptions C Use of SDP for RTSP Session Descriptions
The Session Description Protocol (SDP, RFC 2327 [6]) may be used to The Session Description Protocol (SDP, RFC 2327 [24]) may be used to
describe streams or presentations in RTSP. Such usage is limited to describe streams or presentations in RTSP. This description is typi-
specifying means of access and encoding(s) for: 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
aggregate control: A presentation composed of streams from one an ANNOUNCE method from the client to the server.
or more servers that are available for aggregate control.
Such a description is typically retrieved by HTTP or other
non-RTSP means. However, they may be received with
ANNOUNCE methods.
non-aggregate control: A presentation composed of multiple
streams from a single server that are not available for
aggregate control. Such a description is typically
returned in reply to a DESCRIBE request on a URL, or
received in an ANNOUNCE method.
This appendix describes how an SDP file, retrieved, for example, This appendix describes how an SDP file determines the operation of
through HTTP, determines the operation of an RTSP session. It also an RTSP session. SDP provides no mechanism by which a client can
describes how a client should interpret SDP content returned in reply distinguish, without human guidance, between several media streams to
to a DESCRIBE request. SDP provides no mechanism by which a client be rendered simultaneously and a set of alternatives (e.g., two audio
can distinguish, without human guidance, between several media streams spoken in different languages).
streams to be rendered simultaneously and a set of alternatives
(e.g., two audio streams spoken in different languages).
C.1 Definitions C.1 Definitions
The terms "session-level", "media-level" and other key/attribute The terms "session-level", "media-level" and other key/attribute
names and values used in this appendix are to be used as defined in names and values used in this appendix are to be used as defined in
SDP (RFC 2327 [6]): SDP (RFC 2327 [24]):
C.1.1 Control URL C.1.1 Control URL
The "a=control:" attribute is used to convey the control URL. This The "a=control:" attribute is used to convey the control URL. This
attribute is used both for the session and media descriptions. If attribute is used both for the session and media descriptions. If
used for individual media, it indicates the URL to be used for used for individual media, it indicates the URL to be used for con-
controlling that particular media stream. If found at the session trolling that particular media stream. If found at the session level,
level, the attribute indicates the URL for aggregate control. the attribute indicates the URL for aggregate control.
Example: Example:
a=control:rtsp://example.com/foo a=control:rtsp://example.com/foo
This attribute may contain either relative and absolute URLs, This attribute may contain either relative and absolute URLs, follow-
following the rules and conventions set out in RFC 1808 [28]. ing the rules and conventions set out in RFC 1808 [25]. Implementa-
Implementations should look for a base URL in the following order: tions should look for a base URL in the following order:
1. the RTSP Content-Base field; 1. the RTSP Content-Base field;
2. the RTSP Content-Location field; 2. the RTSP Content-Location field;
3. the RTSP request URL. 3. the RTSP request URL.
If this attribute contains only an asterisk (*), then the URL is If this attribute contains only an asterisk (*), then the URL is
treated as if it were an empty embedded URL, and thus inherits the treated as if it were an empty embedded URL, and thus inherits the
entire base URL. entire base URL.
C.1.2 Media Streams C.1.2 Media Streams
The "m=" field is used to enumerate the streams. It is expected that The "m=" field is used to enumerate the streams. It is expected that
all the specified streams will be rendered with appropriate all the specified streams will be rendered with appropriate synchro-
synchronization. If the session is unicast, the port number serves as nization. If the session is unicast, the port number serves as a rec-
a recommendation from the server to the client; the client still has ommendation from the server to the client; the client still has to
to include it in its SETUP request and may ignore this include it in its SETUP request and may ignore this recommendation.
recommendation. If the server has no preference, it SHOULD set the If the server has no preference, it SHOULD set the port number value
port number value to zero. to zero.
Example: Example:
m=audio 0 RTP/AVP 31 m=audio 0 RTP/AVP 31
C.1.3 Payload Type(s) C.1.3 Payload Type(s)
The payload type(s) are specified in the "m=" field. In case the The payload type(s) are specified in the "m=" field. In case the pay-
payload type is a static payload type from RFC 1890 [1], no other load type is a static payload type from RFC 1890 [1], no other infor-
information is required. In case it is a dynamic payload type, the mation is required. In case it is a dynamic payload type, the media
media attribute "rtpmap" is used to specify what the media is. The attribute "rtpmap" is used to specify what the media is. The "encod-
"encoding name" within the "rtpmap" attribute may be one of those ing name" within the "rtpmap" attribute may be one of those specified
specified in RFC 1890 (Sections 5 and 6), or an experimental encoding in RFC 1890 (Sections 5 and 6), or an experimental encoding with a
with a "X-" prefix as specified in SDP (RFC 2327 [6]). Codec-specific "X-" prefix as specified in SDP (RFC 2327 [24]). Codec-specific
parameters are not specified in this field, but rather in the "fmtp" parameters are not specified in this field, but rather in the "fmtp"
attribute described below. Implementors seeking to register new attribute described below. Implementors seeking to register new
encodings should follow the procedure in RFC 1890 [1]. If the media 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 type is not suited to the RTP AV profile, then it is recommended that
a new profile be created and the appropriate profile name be used in a new profile be created and the appropriate profile name be used in
lieu of "RTP/AVP" in the "m=" field. lieu of "RTP/AVP" in the "m=" field.
C.1.4 Format-Specific Parameters C.1.4 Format-Specific Parameters
Format-specific parameters are conveyed using the "fmtp" media Format-specific parameters are conveyed using the "fmtp" media
skipping to change at page 1, line 3719 skipping to change at page 1, line 4046
encoding(s) that the attribute refers to. Note that the packetization encoding(s) that the attribute refers to. Note that the packetization
interval is conveyed using the "ptime" attribute. interval is conveyed using the "ptime" attribute.
C.1.5 Range of Presentation C.1.5 Range of Presentation
The "a=range" attribute defines the total time range of the stored 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 session. (The length of live sessions can be deduced from the "t" and
"r" parameters.) Unless the presentation contains media streams of "r" parameters.) Unless the presentation contains media streams of
different durations, the length attribute is a session-level different durations, the length attribute is a session-level
attribute. The unit is specified first, followed by the value range. attribute. The unit is specified first, followed by the value range.
The units and their values are as defined in Section 3.5, 3.6 and The units and their values are as defined in Section 3.4, 3.5 and
3.7. 3.6.
Examples: Examples:
a=range:npt=0-34.4368 a=range:npt=0-34.4368
a=range:clock=19971113T2115-19971113T2203 a=range:clock=19971113T2115-19971113T2203
C.1.6 Time of Availability C.1.6 Time of Availability
The "t=" field MUST contain suitable values for the start and stop The "t=" field MUST contain suitable values for the start and stop
times for both aggregate and non-aggregate stream control. With times for both aggregate and non-aggregate stream control. With
aggregate control, the server SHOULD indicate a stop time value for aggregate control, the server SHOULD indicate a stop time value for
which it guarantees the description to be valid, and a start time 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 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 received. It MAY also indicate start and stop times of 0, meaning
that the session is always available. With non-aggregate control, the that the session is always available. With non-aggregate control, the
values should reflect the actual period for which the session is values should reflect the actual period for which the session is
available in keeping with SDP semantics, and not depend on other available in keeping with SDP semantics, and not depend on other
means (such as the life of the web page containing the description) means (such as the life of the web page containing the description)
skipping to change at page 1, line 3753 skipping to change at page 1, line 4081
stream. However, for on-demand unicast streams and some multicast stream. However, for on-demand unicast streams and some multicast
streams, the destination address is specified by the client via the streams, the destination address is specified by the client via the
SETUP request. Unless the media content has a fixed destination SETUP request. Unless the media content has a fixed destination
address, the "c=" field is to be set to a suitable null value. For 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". addresses of type "IP4", this value is "0.0.0.0".
C.1.8 Entity Tag C.1.8 Entity Tag
The optional "a=etag" attribute identifies a version of the session The optional "a=etag" attribute identifies a version of the session
description. It is opaque to the client. SETUP requests may include description. It is opaque to the client. SETUP requests may include
this identifier in the If-Match field (see section 12.23) to only this identifier in the If-Match field (see section 12.22) to only
allow session establishment if this attribute value still corresponds allow session establishment if this attribute value still corresponds
to that of the current description. The attribute value is opaque to that of the current description. The attribute value is opaque
and may contain any character allowed within SDP attribute values. and may contain any character allowed within SDP attribute values.
Example: Example:
a=etag:158bb3e7c7fd62ce67f12b533f06b83a a=etag:158bb3e7c7fd62ce67f12b533f06b83a
One could argue that the "o=" field provides identical One could argue that the "o=" field provides identical func-
functionality. However, it does so in a manner that would tionality. However, it does so in a manner that would put
put constraints on servers that need to support multiple constraints on servers that need to support multiple session
session description types other than SDP for the same piece description types other than SDP for the same piece of media
of media content. content.
C.2 Aggregate Control Not Available C.2 Aggregate Control Not Available
If a presentation does not support aggregate control and multiple If a presentation does not support aggregate control and multiple
media sections are specified, each section MUST have the control URL media sections are specified, each section MUST have the control URL
specified via the "a=control:" attribute. specified via the "a=control:" attribute.
Example: Example:
v=0 v=0
skipping to change at page 1, line 3790 skipping to change at page 1, line 4118
t=0 0 t=0 0
m=video 8002 RTP/AVP 31 m=video 8002 RTP/AVP 31
a=control:rtsp://audio.com/movie.aud a=control:rtsp://audio.com/movie.aud
m=audio 8004 RTP/AVP 3 m=audio 8004 RTP/AVP 3
a=control:rtsp://video.com/movie.vid a=control:rtsp://video.com/movie.vid
Note that the position of the control URL in the description implies Note that the position of the control URL in the description implies
that the client establishes separate RTSP control sessions to the that the client establishes separate RTSP control sessions to the
servers audio.com and video.com servers audio.com and video.com
It is recommended that an SDP file contains the complete media It is recommended that an SDP file contains the complete media ini-
initialization information even if it is delivered to the media tialization information even if it is delivered to the media client
client through non-RTSP means. This is necessary as there is no through non-RTSP means. This is necessary as there is no mechanism to
mechanism to indicate that the client should request more detailed indicate that the client should request more detailed media stream
media stream information via DESCRIBE. information via DESCRIBE.
C.3 Aggregate Control Available C.3 Aggregate Control Available
In this scenario, the server has multiple streams that can be In this scenario, the server has multiple streams that can be con-
controlled as a whole. In this case, there are both a media-level trolled as a whole. In this case, there are both a media-level
"a=control:" attributes, which are used to specify the stream URLs, "a=control:" attributes, which are used to specify the stream URLs,
and a session-level "a=control:" attribute which is used as the and a session-level "a=control:" attribute which is used as the
request URL for aggregate control. If the media-level URL is request URL for aggregate control. If the media-level URL is rela-
relative, it is resolved to absolute URLs according to Section C.1.1 tive, it is resolved to absolute URLs according to Section C.1.1
above. above.
If the presentation comprises only a single stream, the media-level If the presentation comprises only a single stream, the media-level
"a=control:" attribute may be omitted altogether. However, if the "a=control:" attribute may be omitted altogether. However, if the
presentation contains more than one stream, each media stream section presentation contains more than one stream, each media stream section
MUST contain its own "a=control" attribute. MUST contain its own "a=control" attribute.
Example: Example:
v=0 v=0
skipping to change at page 1, line 3826 skipping to change at page 1, line 4154
i=<more info> i=<more info>
c=IN IP4 0.0.0.0 c=IN IP4 0.0.0.0
t=0 0 t=0 0
a=control:rtsp://example.com/movie/ a=control:rtsp://example.com/movie/
m=video 8002 RTP/AVP 31 m=video 8002 RTP/AVP 31
a=control:trackID=1 a=control:trackID=1
m=audio 8004 RTP/AVP 3 m=audio 8004 RTP/AVP 3
a=control:trackID=2 a=control:trackID=2
In this example, the client is required to establish a single RTSP In this example, the client is required to establish a single RTSP
session to the server, and uses the URLs session to the server, and uses the URLs rtsp://exam-
rtsp://example.com/movie/trackID=1 and ple.com/movie/trackID=1 and rtsp://example.com/movie/trackID=2 to set
rtsp://example.com/movie/trackID=2 to set up the video and audio up the video and audio streams, respectively. The URL rtsp://exam-
streams, respectively. The URL rtsp://example.com/movie/ controls the ple.com/movie/ controls the whole movie.
whole movie.
A client is not required to issues SETUP requests for all streams A client is not required to issues SETUP requests for all streams |
within an aggregate object. Servers SHOULD allow the client to ask within an aggregate object. Servers SHOULD allow the client to ask |
for only a subset of the streams. for only a subset of the streams.
D Minimal RTSP implementation D Minimal RTSP implementation
D.1 Client D.1 Client
A client implementation MUST be able to do the following : A client implementation MUST be able to do the following :
o Generate the following requests: SETUP, TEARDOWN, and one of + Generate the following requests: SETUP, TEARDOWN, and one of PLAY
PLAY (i.e., a minimal playback client) or RECORD (i.e., a (i.e., a minimal playback client) or RECORD (i.e., a minimal
minimal recording client). If RECORD is implemented, ANNOUNCE recording client). If RECORD is implemented, ANNOUNCE MUST be
MUST be implemented as well. implemented as well.
o Include the following headers in requests: CSeq, Connection, + Include the following headers in requests: CSeq, Connection, Ses-
Session, Transport. If ANNOUNCE is implemented, the sion, Transport. If ANNOUNCE is implemented, the capability to
capability to include headers Content-Language, Content- include headers Content-Language, Content-Encoding, Content-
Encoding, Content-Length, and Content-Type should be as well. Length, and Content-Type should be as well.
o Parse and understand the following headers in responses: + Parse and understand the following headers in responses: CSeq,
CSeq, Connection, Session, Transport, Content-Language, Connection, Session, Transport, Content-Language, Content-Encod-
Content-Encoding, Content-Length, Content-Type. If RECORD is ing, Content-Length, Content-Type. If RECORD is implemented, the
implemented, the Location header must be understood as well. Location header must be understood as well. RTP-compliant imple-
RTP-compliant implementations should also implement RTP-Info. mentations should also implement RTP-Info.
o Understand the class of each error code received and notify + Understand the class of each error code received and notify the
the end-user, if one is present, of error codes in classes 4xx end-user, if one is present, of error codes in classes 4xx and
and 5xx. The notification requirement may be relaxed if the 5xx. The notification requirement may be relaxed if the end-user
end-user explicitly does not want it for one or all status explicitly does not want it for one or all status codes.
codes.
o Expect and respond to asynchronous requests from the server, + Expect and respond to asynchronous requests from the server, such
such as ANNOUNCE. This does not necessarily mean that it as ANNOUNCE. This does not necessarily mean that it should imple-
should implement the ANNOUNCE method, merely that it MUST ment the ANNOUNCE method, merely that it MUST respond positively
respond positively or negatively to any request received from or negatively to any request received from the server.
the server.
Though not required, the following are RECOMMENDED. Though not required, the following are RECOMMENDED.
o Implement RTP/AVP/UDP as a valid transport. + Implement RTP/AVP/UDP as a valid transport.
o Inclusion of the User-Agent header. + Inclusion of the User-Agent header.
o Understand SDP session descriptions as defined in Appendix C + Understand SDP session descriptions as defined in Appendix C
o Accept media initialization formats (such as SDP) from + Accept media initialization formats (such as SDP) from standard
standard input, command line, or other means appropriate to input, command line, or other means appropriate to the operating
the operating environment to act as a "helper application" for environment to act as a "helper application" for other applica-
other applications (such as web browsers). tions (such as web browsers).
There may be RTSP applications different from those There may be RTSP applications different from those initially
initially envisioned by the contributors to the RTSP