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Versions: (RFC 3555) 00 01 02 03 04 05 RFC 4855

Internet Engineering Task Force      Audio/Video Transport Working Group
INTERNET-DRAFT                                                 S. Casner
draft-ietf-avt-rfc3555bis-00.txt                           Packet Design
                                                              P. Hoschka
                                                           W3C/INRIA/MIT
                                                           July 10, 2005
                                               Expires: January 10, 2006


             MIME Type Registration of RTP Payload Formats

Status of this Memo

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This Internet-Draft will expire on January 10, 2006.

Copyright Notice

Copyright (C) The Internet Society (2005).

                                Abstract

     This document defines the procedure to register RTP Payload Formats
     as audio, video or other MIME subtype names.  This is useful in a
     text-based format or control protocol to identify the type of an
     RTP transmission.  This document also registers all the RTP payload
     formats defined in the RTP Profile for Audio and Video Conferences
     as MIME subtypes.  Some of these may also be used for transfer
     modes other than RTP.



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Table of Contents

   1. Introduction ..................................................  3
      1.1. IANA Considerations ......................................  3
      1.2. Terminology ..............................................  4
   2. Procedure For Registering MIME Types for RTP Payload Types ....  4
      2.1. Restrictions on Sharing a Type ...........................  6
   3. Mapping to SDP Parameters .....................................  6
   4. Registrations for "Audio/Video Profile" .......................  8
      4.1. Audio Type Registrations .................................  8
      4.2. Video Type Registrations ................................. 28
   5. Changes from RFC 3555 ......................................... 38
   6. Security Considerations ....................................... 38
   7. Normative References .......................................... 39
   8. Authors' Addresses ............................................ 39
   9. Intellectual Property Statement ............................... 40
  10. Disclaimer of Validity ........................................ 40
  11. Copyright Statement ........................................... 41

































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1.  Introduction

The MIME registration procedure described in RFC 2048 [1] was originally
designed for transport of multimedia information via asynchronous
Internet mail, but the MIME namespace now provides identification for
other transport modes as well.  Updated registration procedures are
specified in [2].  This document defines the procedure to register MIME
subtype names for use with the Real-time Transport Protocol (RTP), RFC
3550 [3], to identify RTP payload formats.

This document also registers all the RTP payload formats defined in the
RTP Profile for Audio and Video Conferences, RFC 3551 [4], as MIME
subtypes under the "audio" and "video" MIME types.

1.1.  IANA Considerations

This document registers the following MIME subtypes:

     audio/DVI4
     audio/G722
     audio/G723
     audio/G726-16
     audio/G726-24
     audio/G726-32
     audio/G726-40
     audio/G728
     audio/G729
     audio/G729D
     audio/G729E
     audio/GSM
     audio/GSM-EFR
     audio/L8
     audio/L16
     audio/LPC
     audio/MPA
     audio/PCMA
     audio/PCMU
     audio/QCELP
     audio/RED
     audio/VDVI











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     video/BT656
     video/CelB
     video/JPEG
     video/H261
     video/H263
     video/H263-1998
     video/H263-2000
     video/MPV
     video/MP2T
     video/MP1S
     video/MP2P
     video/BMPEG
     video/nv


MIME subtype audio/L16 has already been registered via RFC 2586 for
transports other than RTP.  That registration is incorporated here and
augmented with additional information for RTP transport.

1.2.  Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [5] and indicate
requirement levels for implementations compliant with this
specification.

2.  Procedure For Registering MIME Types for RTP Payload Types

Registering an RTP payload type as a MIME type follows the same
procedures as described in [2] and uses the registration template shown
in Section 10 of [2].  Some additional parameters are required to
specify how a particular payload format is transported over RTP:

     Published specification
          A description of the media encoding and a specification of the
          payload format must be provided, usually by reference to an
          RTP payload format specification RFC.  That RFC may be
          separate, or the MIME subtype registration may be incorporated
          into the payload format specification RFC.  The payload format
          specification MUST include the RTP timestamp clock rate (or
          multiple rates for audio encodings with multiple sampling
          rates).

          A reference to a further description of the data compression
          format itself should be provided, if available.





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     Required parameters
          If the payload format does not have a fixed RTP timestamp
          clock rate, then a "rate" parameter is required to specify the
          RTP timestamp clock rate.  A particular payload format may
          have additional required parameters.

     Optional parameters
          Most audio payload formats can have an optional "channels"
          parameter to specify the number of audio channels included in
          the transmission.  Any payload format, but most likely audio
          formats, may also include the optional parameters "ptime", to
          specify the recommended length of time in milliseconds
          represented by the media in a packet, and/or "maxptime" to
          specify the maximum amount of media which can be encapsulated
          in each packet, expressed as time in milliseconds.  The
          "ptime" and "maxptime" parameters are defined in the Session
          Description Protocol (SDP) [6].

          A particular payload format may have additional optional
          parameters.

     Encoding considerations
          Most RTP payload formats include binary or framed data as
          described in Section 4.8 of [2].  The appropriate encoding
          considerations MUST be noted.

     Restrictions on usage:
          The fact that the type is defined for transfer via RTP MUST be
          noted, in particular if the transfer depends on RTP framing
          and hence the type is only defined for transfer via RTP.

Depending on whether the type has already been registered for transfer
with a non-RTP protocol (e.g. MIME mail or http) or not, several
different cases can occur:

     a) Not yet registered as a MIME type

        A new registration should be constructed using the MIME
        registration template.  The registration may specify transfer
        via other means in addition to RTP if that is feasible and
        desired.  The appropriate encoding considerations must be
        specified, and the restrictions on usage must specify whether
        the type is only defined for transfer via RTP or via other modes
        as well.

        Optional parameters may be defined as needed, and it must be
        clearly stated to which mode(s) of transfer the parameters
        apply.



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     b) MIME type exists for a non-RTP protocol

        The restrictions on usage of the existing type should be
        changed, if present, or added, if not, to indicate that the type
        can also be transferred via RTP.

        RTP-specific parameters may be added, and it must be clearly
        stated that these are only to be used when the media type is
        transmitted via RTP transport.

     c) Update an existing MIME type for RTP to be used for a non-RTP
        protocol

        The restrictions on usage of the existing type should be changed
        to indicate that the type can also be transferred via a non-RTP
        protocol (e.g. SMTP, HTTP).

        Non-RTP-specific parameters can be added, and it must be clearly
        stated that these are only to be used when the media type is
        transmitted via a non-RTP transport.

2.1.  Restrictions on Sharing a Type

The same MIME type MUST NOT be shared for RTP and non-RTP (file-based)
transfer methods unless the data format is the same for both methods.
The data format is considered to be same if the file format is
equivalent to a concatenated sequence of payloads from RTP packets not
including the RTP header or any payload-format header.

The file format MAY include a magic number or other header at the start
of the file that is not included when the data is transferred via RTP.

A second requirement for sharing a MIME type is that the sets of
required parameters must be the same for both methods.

For cases where the data format or required parameters cannot be the
same for RTP and non-RTP transfer methods, then the data formats MUST be
registered as separate types.  It is RECOMMENDED that the type names be
related, such as by using a common root plus a suffix.

3.  Mapping to SDP Parameters

The representation of a MIME media type is specified in the syntax of
the Content-Type header field in RFC 2045 [7] as follows:

     type "/" subtype  *(";" parameter)





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Parameters may be required for a particular type or subtype or they may
be optional.  For media types which represent RTP payload formats, the
parameters "rate", "channels", "ptime", and "maxptime" have general
definitions (given above) that may apply across types and subtypes.  The
format for a parameter is specified in RFC 2045 as

     attribute "=" value

where attribute is the parameter name and the permissible values are
specified for each parameter.  The value may need to be a quoted string
if it contains any of the special characters listed in RFC 2045.

The information carried in the media type string has a specific mapping
to fields in the Session Description Protocol (SDP) [6], which is
commonly used to describe RTP sessions.  The mapping is as follows:

    o  The MIME type (e.g., audio) goes in SDP "m=" as the media name.

    o  The MIME subtype (payload format) goes in SDP "a=rtpmap" as the
       encoding name.

    o  The general (possibly optional) parameters "rate" and "channels"
       also go in "a=rtpmap" as clock rate and encoding parameters,
       respectively.

    o  The general (and optional) parameters "ptime" and "maxptime" go
       in the SDP "a=ptime" and "a=maxptime" attributes, respectively.

    o  Any payload-format-specific parameters go in the SDP "a=fmtp"
       attribute.  The set of allowed parameters is defined by the RFC
       that specifies the payload format and MUST NOT be extended by the
       MIME subtype registration without a corresponding revision of the
       payload format specification.  The format and syntax of these
       parameters may also be defined by the payload format
       specification, but it is suggested that the parameters be copied
       directly from the MIME media type string as a semicolon separated
       list of parameter=value pairs.  For payload formats that specify
       some other syntax for the fmtp parameters, the registration of
       that payload format as a MIME subtype must specify what the
       parameters are in MIME format and how to map them to the SDP
       "a=fmtp" attribute.  See Section 4.1.21 for an example.

An example mapping is as follows:








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        audio/L16; rate=48000; channels=2; ptime=5; emphasis=50-15

        m=audio 49170 RTP/AVP 97
        a=rtpmap:97 L16/48000/2
        a=fmtp:97 emphasis=50-15
        a=ptime:5

Note that the payload format (encoding) names defined in the RTP Profile
are commonly shown in upper case.  MIME subtypes are commonly shown in
lower case.  These names are case-insensitive in both places.
Similarly, parameter names are case-insensitive both in MIME types and
in the default mapping to the SDP a=fmtp attribute.

4.  Registrations for "Audio/Video Profile"

In the following sections, all RTP payload formats described in the RTP
Profile for Audio and Video Conferences, RFC 3551 [4], are registered as
MIME subtypes.

4.1.  Audio Type Registrations

The following sections register all of the RTP audio payload types
defined in RFC 3551 as MIME types.

For most audio payload formats, the RTP timestamp clock rate is equal to
the sampling rate.  Some payload formats operate only at one fixed
sampling rate, while others are adjustable.

4.1.1.  Registration of MIME media type audio/DVI4

     MIME media type name: audio

     MIME subtype name: DVI4

     Required parameters: rate
          The RTP timestamp clock rate, which is equal to the sampling
          rate.  The typical rate is 8000, but other rates may be
          specified.

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555





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     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.2.  Registration of MIME media type audio/G722

     MIME media type name: audio

     MIME subtype name: G722

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>




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     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.3.  Registration of MIME media type audio/G723

     MIME media type name: audio

     MIME subtype name: G723

     Required parameters: None

     Optional parameters:
          ptime, maxptime

          bitrate: the data rate in kb/s used or preferred for the audio
          bit stream, with permissible values 5.3 or 6.3.  If
          unspecified, the bitrate may change from frame to frame as
          indicated inband.

          annexa: indicates that Annex A, voice activity detection, is
          used or preferred.  Permissible values are "yes" and "no"
          (without the quotes); "yes" is implied if this parameter is
          omitted.

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>





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     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.4.  Registration of MIME media type audio/G726-16

     MIME media type name: audio

     MIME subtype name: G726-16

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.5.  Registration of MIME media type audio/G726-24

     MIME media type name: audio




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     MIME subtype name: G726-24

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.6.  Registration of MIME media type audio/G726-32

     MIME media type name: audio

     MIME subtype name: G726-32

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555




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     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.7.  Registration of MIME media type audio/G726-40

     MIME media type name: audio

     MIME subtype name: G726-40

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>




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     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.8.  Registration of MIME media type audio/G728

     MIME media type name: audio

     MIME subtype name: G728

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.9.  Registration of MIME media type audio/G729

     MIME media type name: audio




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     MIME subtype name: G729

     Required parameters: None

     Optional parameters:
          ptime, maxptime

          annexb: indicates that Annex B, voice activity detection, is
          used or preferred.  Permissible values are "yes" and "no"
          (without the quotes); "yes" is implied if this parameter is
          omitted.

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.10.  Registration of MIME media type audio/G729D

     MIME media type name: audio

     MIME subtype name: G729D

     Required parameters: None

     Optional parameters:
          ptime, maxptime



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          annexb: indicates that Annex B, voice activity detection, is
          used or preferred.  Permissible values are "yes" and "no"
          (without the quotes); "yes" is implied if this parameter is
          omitted.

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.11.  Registration of MIME media type audio/G729E

     MIME media type name: audio

     MIME subtype name: G729E

     Required parameters: None

     Optional parameters:
          ptime, maxptime

          annexb: indicates that Annex B, voice activity detection, is
          used or preferred.  Permissible values are "yes" and "no"
          (without the quotes); "yes" is implied if this parameter is
          omitted.





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     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.12.  Registration of MIME media type audio/GSM

     MIME media type name: audio

     MIME subtype name: GSM

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.



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     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.13.  Registration of MIME media type audio/GSM-EFR

     MIME media type name: audio

     MIME subtype name: GSM-EFR

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner



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4.1.14.  Registration of MIME media type audio/L8

     MIME media type name: audio

     MIME subtype name: L8

     Required parameters: rate, the RTP timestamp clock rate

     Optional parameters: channels, ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.15.  Registration of MIME media type audio/L16

MIME subtype audio/L16 has already been registered via RFC 2586 for
transports other than RTP.  That registration is incorporated here and
augmented with additional information for RTP transport.

     MIME media type name: audio

     MIME subtype name: L16

     Required parameters
          rate: number of samples per second -- For non-RTP transport,



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          the permissible values for rate are 8000, 11025, 16000, 22050,
          24000, 32000, 44100, and 48000 samples per second.  For RTP
          transport, other values are permissible but the aforementioned
          values are RECOMMENDED.  For RTP, the rate parameter indicates
          the RTP timestamp clock rate, which is equal to the sample
          rate.

     Optional parameters
          channels: how many audio streams are interleaved -- defaults
          to 1; stereo would be 2, etc.  Interleaving takes place
          between individual two-byte samples.

          emphasis: analog preemphasis applied to the signal before
          quantization.  The only emphasis value defined here is
          emphasis=50-15 to indicate the 50/15 microsecond preemphasis
          used with Compact Disks.  This parameter MUST be omitted if no
          analog preemphasis was applied.

          channel-order: specifies the sample interleaving order for
          multiple-channel audio streams (see [8] Section 7).
          Permissible values are DV.LRLsRs, DV.LRCS, DV.LRCWo,
          DV.LRLsRsC, DV.LRLsRsCS, DV.LmixRmixTWoQ1Q2,
          DV.LRCWoLsRsLmixRmix, DV.LRCWoLs1Rs1Ls2Rs2, DV.LRCWoLsRsLcRc.
          For interoperation with DV video systems, only a subset of
          these channel combinations is specified for use with 20-bit
          linear encoding in the DV video specification [5]; those are
          DV.LRLsRs, DV.LRCS, DV.LmixRmixTWoQ1Q2.  This parameter MUST
          be omitted when the AIFF-C channel order convention (see RFC
          3551) is in use.

          For RTP, ptime: RECOMMENDED duration of each packet in
          milliseconds.

          For RTP, maxptime: maximum duration of each packet in
          milliseconds.

     Encoding considerations
          Audio data is binary data, and must be encoded for non-binary
          transport; the Base64 encoding is suitable for Email.  Note
          that audio data does not compress easily using lossless
          compression.

     Security considerations
          Audio data is believed to offer no security risks.
          See Section 5 of RFC 3555.

     Interoperability considerations
          This type is compatible with the encoding used in the WAV



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          (Microsoft Windows RIFF) and Apple AIFF union types, and with
          the public domain "sox" and "rateconv" programs.

     Published specification
          RFC 2586 for non-RTP transports, RFC 3551 for RTP

     Applications which use this media
          The public domain "sox" and "rateconv" programs accept this
          type.

          1. Magic number(s) : None
          2. File extension(s) : WAV L16
          3. Macintosh file type code : AIFF


     Person to contact for further information
          1. Name : James Salsman
          2. E-mail : jps-L16@bovik.org

     Intended usage
          Common

          It is expected that many audio and speech applications will
          use this type.  Already the most popular platforms provide
          this type with the rate=11025 parameter referred to as "radio
          quality speech."

     Restrictions on usage
          In addition to file-based transfer methods, this type is also
          defined for transfer via RTP [RFC 3550].

     Author/Change controller
          James Salsman for non-RTP transports.
          Stephen Casner for RTP transport.

4.1.16.  Registration of MIME media type audio/LPC

     MIME media type name: audio

     MIME subtype name: LPC

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).



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     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.17.  Registration of MIME media type audio/MPA

     MIME media type name: audio

     MIME subtype name: MPA (MPEG audio)

     Required parameters: None

     Optional parameters:
          layer: which layer of MPEG audio encoding; permissible values
          are 1, 2, 3.

          samplerate: the rate at which audio is sampled.  MPEG-1 audio
          supports sampling rates of 32, 44.1, and 48 kHz; MPEG-2
          supports sampling rates of 16, 22.05 and 24 kHz.  This
          parameter is separate from the RTP timestamp clock rate which
          is always 90000 Hz for MPA.

          mode: permissible values are "stereo", "joint_stereo",
          "single_channel", "dual_channel".  The "channels" parameter
          does not apply to MPA.  It is undefined to put a number of
          channels in the SDP rtpmap attribute for MPA.

          bitrate: the data rate for the audio bit stream.





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          ptime: RECOMMENDED duration of each packet in milliseconds.

          maxptime: maximum duration of each packet in milliseconds.

          Parameters which are omitted are left to the encoder to choose
          based on the session bandwidth, configuration information, or
          other constraints.  The selected layer as well as the sampling
          rate and mode are indicated in the payload so receivers can
          process the data without these parameters being specified
          externally.

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.18.  Registration of MIME media type audio/PCMA

     MIME media type name: audio

     MIME subtype name: PCMA

     Required parameters: rate
          The RTP timestamp clock rate, which is equal to the sampling
          rate.  The typical rate is 8000, but other rates may be
          specified.




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     Optional parameters: channels, ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.19.  Registration of MIME media type audio/PCMU

     MIME media type name: audio

     MIME subtype name: PCMU

     Required parameters: rate
          The RTP timestamp clock rate, which is equal to the sampling
          rate.  The typical rate is 8000, but other rates may be
          specified.

     Optional parameters: channels, ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555





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     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.20.  Registration of MIME media type audio/QCELP

     MIME media type name: audio

     MIME subtype name: QCELP

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2658

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>




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     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.21.  Registration of MIME media type audio/RED

     MIME media type name: audio

     MIME subtype name: RED

     Required parameters:
          pt: a comma-separated list of RTP payload types.  Because
          comma is a special character, the list must be a quoted-string
          (enclosed in double quotes).  For static payload types, each
          list element is simply the type number.  For dynamic payload
          types, each list element is a mapping of the dynamic payload
          type number to an embedded MIME content-type specification for
          the payload format corresponding to the dynamic payload type.
          The format of the mapping is:

             dynamic-payload-type "=" content-type

          If the content-type string includes a comma, then the content-
          type string MUST be a quoted-string.  If the content-type
          string does not include a comma, it MAY still be quoted.
          Since it is part of the list which must itself be a quoted-
          string, that means the quotation marks MUST be quoted with
          backslash quoting as specified in RFC 2045.  If the content-
          type string itself contains a quoted-string, then the
          requirement for backslash quoting is recursively applied.  To
          specify the audio/RED payload format in SDP, the pt parameter
          is mapped to an a=fmtp attribute by eliminating the parameter
          name (pt) and changing the commas to slashes.  For example,
          'pt="0,5"' maps to 'a=fmtp:99 0/5'.  A more complicated
          example, with a dynamic payload type, is:

             pt = "0, 103 = \"audio/G729D;annexb=yes\" "

             m=audio 49170 RTP/AVP 99 0 103
             a=rtpmap:99 RED/8000
             a=fmtp:99 0/103
             a=rtpmap:103 G729D/8000
             a=fmtp:103 annexb=yes




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     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2198

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.1.22.  Registration of MIME media type audio/VDVI

     MIME media type name: audio

     MIME subtype name: VDVI

     Required parameters: None

     Optional parameters: ptime, maxptime

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551




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     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.  Video Type Registrations

For all of the video payload formats registered here, the RTP timestamp
clock rate is always 90000 Hz, so the "rate" parameter is not
applicable.  Likewise, the "channel" parameter is not used with video,
and while "ptime" and "maxptime" could be used with video, they
typically are not.

4.2.1.  Registration of MIME media type video/BT656

     MIME media type name: video

     MIME subtype name: BT656

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2431

     Applications which use this media type:
          Audio and video streaming and conferencing tools.





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     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.2.  Registration of MIME media type video/CelB

     MIME media type name: video

     MIME subtype name: CelB

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2029

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner



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4.2.3.  Registration of MIME media type video/JPEG

     MIME media type name: video

     MIME subtype name: JPEG

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2435

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.4.  Registration of MIME media type video/H261

     MIME media type name: video

     MIME subtype name: H261

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in



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          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2032

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.5.  Registration of MIME media type video/H263

     MIME media type name: video

     MIME subtype name: H263

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2190

     Applications which use this media type:
          Audio and video streaming and conferencing tools.





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     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.6.  Registration of MIME media type video/H263-1998

     MIME media type name: video

     MIME subtype name: H263-1998

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2429

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner



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4.2.7.  Registration of MIME media type video/H263-2000

     MIME media type name: video

     MIME subtype name: H263-2000

     Required parameters: None

     Optional parameters:
          profile: H.263 profile number, in the range 0 through 10,
          specifying the supported H.263 annexes/subparts.

          level: Level of bitstream operation, in the range 0 through
          100, specifying the level of computational complexity of the
          decoding process.

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2429
          The specific values for the profile and level parameters and
          their meaning are defined in Annex X of ITU-T Recommendation
          H.263, "Video coding for low bit rate communication".  Note
          that the RTP payload format for H263-2000 is the same as for
          H263-1998, but additional annexes/subparts are specified along
          with the profiles and levels.

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner




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4.2.8.  Registration of MIME media type video/MPV

     MIME media type name: video

     MIME subtype name: MPV
          MPEG-1 or -2 Elementary Streams

     Required parameters: None

     Optional parameters:
          type: the type of MPEG video, from the set "mpeg1",
          "mpeg2-halfd1", or "mpeg2-fulld1".  The default is "mpeg1".
          The mapping to a=fmtp is identity.

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2250

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.9.  Registration of MIME media type video/MP2T

     MIME media type name: video

     MIME subtype name: MP2T
          MPEG-2 Transport Streams





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     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2250

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.10.  Registration of MIME media type video/MP1S

     MIME media type name: video

     MIME subtype name: MP1S
          MPEG-1 Systems Streams

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555





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     Interoperability considerations: none

     Published specification: RFC 2250

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.11.  Registration of MIME media type video/MP2P

     MIME media type name: video

     MIME subtype name: MP2P
          MPEG-2 Program Streams

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2250

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>



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     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.12.  Registration of MIME media type video/BMPEG

     MIME media type name: video

     MIME subtype name: BMPEG

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 2343

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

4.2.13.  Registration of MIME media type video/nv

     MIME media type name: video




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     MIME subtype name: nv

     Required parameters: None

     Optional parameters: None

     Encoding considerations:
          This media type is framed binary data (see section 4.8 in
          [2]).

     Security considerations: See Section 5 of RFC 3555

     Interoperability considerations: none

     Published specification: RFC 3551

     Applications which use this media type:
          Audio and video streaming and conferencing tools.

     Additional information: none

     Person & email address to contact for further information:
          Stephen Casner <casner@acm.org>

     Intended usage: COMMON

     Restrictions on usage:
          This type is only defined for transfer via RTP [RFC 3550].

     Author/Change controller:
          Stephen Casner

5.  Changes from RFC 3555

This document updates RFC 3555 to conform to the revised MIME type
registration procedures in [2].  Whereas RFC 3555 required the encoding
considerations to specify transfer via RTP, that is now specified under
restrictions on usage.  This document also adds a new Section 2.1 to
clarify the requirements for sharing a MIME type among RTP and non-RTP
transfer methods.

6.  Security Considerations

The MIME subtype registration procedure specified in this memo does not
impose any security considerations on its own.  This memo also contains
several MIME type registrations.  The registrations themselves do not
impose security risks, but some may state security considerations
specific to the particular registration.



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Several audio and video encodings are perfect for hiding data using
steganography.

The RTP specification, RFC 3550, provides security considerations for
the transport of audio and video data over RTP, including the use of
encryption where confidentiality is required.

7.  Normative References

[1] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet Mail
    Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC
    2048, November 1996.

[2] Freed, N. and J. Klensin, "Media Type Specifications and
    Registration Procedures", draft-freed-media-type-reg-04, April
    2005.

[3] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP:
    A Transport Protocol for Real-Time Applications", RFC 3550, July
    2003.

[4] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
    Conferences with Minimal Control", RFC 3551, July 2003.

[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
    Levels", BCP 14, RFC 2119, March 1997.

[6] Handley, M. and V. Jacobson, "SDP: Session Description
    Protocol", RFC 2327, April 1998.

[7] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions
    (MIME) Part One: Format of Internet Message Bodies", RFC 2045,
    November 1996.

[8] Kobayashi, K., Ogawa, A., Casner, S. and C. Bormann, "RTP Payload
    Format for 12-bit DAT Audio and 20- and 24-bit Linear Sampled
    Audio", RFC 3190, January 2002.

8.  Authors' Addresses

   Stephen L. Casner
   Packet Design
   3400 Hillview Avenue, Building 3
   Palo Alto, CA 94304
   United States

   Phone: +1 650 739-1843
   EMail: casner@acm.org



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   Philipp Hoschka
   INRIA
   Route des Lucioles 2004
   06904, Sophia-Antipolis Cedex
   BP 93, France
   Phone: (+33) 4 92 38 79 84
   Fax:   (+33) 4 92 38 77 65
   EMail: ph@w3.org
   W3C
   http://www.w3.org/people/hoschka

9.  Intellectual Property Statement

The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in this
document or the extent to which any license under such rights might or
might not be available; nor does it represent that it has made any
independent effort to identify any such rights.  Information on the
procedures with respect to rights in RFC documents can be found in BCP
78 and BCP 79.

Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an attempt
made to obtain a general license or permission for the use of such
proprietary rights by implementers or users of this specification can be
obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.

The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary rights
that may cover technology that may be required to implement this
standard.  Please address the information to the IETF at ietf-
ipr@ietf.org.

10.  Disclaimer of Validity

This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR
IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.







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Internet Draft      draft-ietf-avt-rfc3555bis-00.txt             July 10


11.  Copyright Statement

Copyright (C) The Internet Society (2005).

This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors retain
all their rights.












































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