One document matched: draft-marjou-mmusic-sdp-rtsp-00.txt




MMUSIC Working Group                                           X. Marjou
Internet-Draft                                            France Telecom
Expires: April 15, 2007                                     S. Whitehead
                                                                 Verizon
                                                          M.J. Montpetit
                                                              S. Ganesan
                                                                Motorola
                                                                 D. Ress
                                                             D. Goodwill
                                                                  Nortel
                                                        October 12, 2006


   Session Description Protocol (SDP) Format for Real Time Streaming
                        Protocol (RTSP) Streams.
                    draft-marjou-mmusic-sdp-rtsp-00

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   Copyright (C) The Internet Society (2006).

Abstract




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   This document specifies how to describe RTSP streams in SDP session
   descriptions.  Agents using the offer/answer model to establish RTSP
   streams use this format in their offers and their answers.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  RTSP Usage Restriction when used with SDP Offer/Answer . . . .  3
   4.  Procedure at the SDP Offerer . . . . . . . . . . . . . . . . .  4
     4.1.  Offerer is an RTSP Client  . . . . . . . . . . . . . . . .  4
     4.2.  Offerer is an RTSP Server  . . . . . . . . . . . . . . . .  5
   5.  Procedure at the SDP Answerer  . . . . . . . . . . . . . . . .  6
     5.1.  Answerer is an RTSP Server . . . . . . . . . . . . . . . .  6
     5.2.  Answerer is an RTSP Client . . . . . . . . . . . . . . . .  7
   6.  Fields in the 'm' Line . . . . . . . . . . . . . . . . . . . .  7
   7.  RTSP Grouping of Media Lines . . . . . . . . . . . . . . . . .  8
   8.  Mapping of RTSP Parameters to SDP Attributes . . . . . . . . .  8
     8.1.  RTSP Version . . . . . . . . . . . . . . . . . . . . . . .  9
     8.2.  RTSP Request-URI . . . . . . . . . . . . . . . . . . . . .  9
     8.3.  RTSP Header Attributes . . . . . . . . . . . . . . . . . .  9
     8.4.  RTSP Vendor Specific Attributes  . . . . . . . . . . . . .  9
   9.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
     11.1. Registration of the 'TCP/RTSP' and 'TCL/TLS/RTSP' SDP
           'Proto'  . . . . . . . . . . . . . . . . . . . . . . . . . 12
     11.2. Registration of the SDP 'rtspid' Attribute . . . . . . . . 12
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     13.2. Normative References . . . . . . . . . . . . . . . . . . . 13
     13.3. Informational References . . . . . . . . . . . . . . . . . 14
   Appendix A.  A SIP-RTSP call-flow example  . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
   Intellectual Property and Copyright Statements . . . . . . . . . . 18















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1.  Introduction

   The Real Time Streaming Protocol [1] [2], or RTSP, is an application-
   level protocol for control over the delivery of data with real-time
   properties.

   Although RTSP works perfectly well as a standalone protocol, there
   are some use-cases where it is desirable to establish an RTSP session
   using an offer/answer exchange [3], as discussed in [4].

   A first example of use-case is a scenario mixing video-surveillance
   with a regular call: a user monitors a remote scene, possibly with
   trick play commands, and when a remote user appears at the remote
   scene, he engages a multimedia conversation with this remote user.

   A second example of use-case is a scenario where trick play commands
   are possible within a conference.  A user joins a conference late and
   uses a fast rewind command to come back to the beginning of the
   presentation and possibly learn the names of the participants.

   This document therefore describes how to setup an RTSP session with
   the SDP offer/answer model.

   Section 3 details the minor restrictions associated to RTSP when used
   together with the offer/answer.  Section 4 and Section 5 rule-out the
   detailed behavior of an SDP offerer and answerer.  Section 6 details
   the media line associated to an RTSP stream.  Section 7 defines a new
   extension for grouping the media lines of the RTSP media stream and
   the other media streams that are under its control.  Section 8
   defines the mapping between some existing RTSP attributes and new SDP
   parameters.


2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in RFC 2119 [5]


3.  RTSP Usage Restriction when used with SDP Offer/Answer

   In this specification, a session signalling protocol (typically SIP)
   is used to establish an RTSP stream via an SDP offer/answer.  This
   session signalling protocol initiates, modifies and terminates the
   media session.  Therefore, when used in the context of SDP offer/
   answer, the RTSP SETUP and TEARDOWN requests MUST NOT be used within
   the RTSP stream.  Similarly, the RTSP REDIRECT request MUST NOT be



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   used, as it is the responsibility of the session signalling protocol
   to perform redirections.

   In the same vein, the description of the targeted presentation or
   media object makes part of the SDP offer/answer.  Therefore, the RTSP
   DESCRIBE and ANNOUNCE requests MUST NOT be used.

   This implies consequences on the existing rules of [1] and [2] for
   the life of an RTSP session.
   o  The RTSP session MUST also be able to start right after an
      accepted SDP offer followed by an RTSP transport connection.
   o  The RTSP session MUST also be able to terminate either at the
      reception of new SDP offer with the port number for that stream
      set to zero or at the reception of a terminating session
      signalling message(typically a SIP BYE).

   The removal of DESCRIBE and SETUP requests also has some impacts:
   o  An alternate means of conveying some of their parameters is
      needed.  This is described in Section 8 that specifies how to
      convey an RTSP Request-URI, an RTSP-Version and necessary RTSP
      header fields.
   o  Another notable difference concerns two RTSP header fields.  As
      the transport parameters are negotiated within the SDP offer/
      answer, the Transport header field is not used anymore.  In
      addition, there is no RTSP CSeq attribute in the SDP offer/answer.

   In addition, the following topics are considered out of scope and not
   discussed further in this document: RTSP over UDP, NAT traversal,
   embedded (interleaved) binary data.

   [[OPEN-ISSUE-1: There is currently no consensus amongst the authors
   on whether the SETUP and DESCRIBE methods should be kept or not.  If
   the SETUP and DESCRIBE methods are not used, then the number of
   message round-trips is less important and the integration with the
   SDP offer/answer mechanism is feasible.  On the other side, if they
   are still used, then no RTSP header field parameters need to be
   conveyed within SDP offer and answer and the integration with
   existing RTSP servers is easier.]]


4.  Procedure at the SDP Offerer

4.1.  Offerer is an RTSP Client

   When an agent wishes to offer the role of an RTSP client, it has to
   perform the actions described in this section.

   It MUST offer a 'm' line for an RTSP stream (c.f.  Section 6).  It



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   MUST also indicate that it will initiate the outgoing connection for
   this stream as described in [6].  Typically, the port number should
   be a port number of 9 (the discard port) on its 'm' line, and the
   'setup' attribute is set to 'active'.

   If it is attempting to establish a new RTSP session, it MUST NOT
   include the RTSP session header in the offer.  Otherwise, if it wants
   to reuse an existing RTSP session, it MUST add it in a "fmtp:rtsp
   h-session" attribute.

   In order to identify the targeted presentation or media object, it
   MAY include an RTSP Request-URI in a "fmtp:rtsp uri" parameter.
   Otherwise, expressing the targeted content will be the responsibility
   of the session signalling protocol (e.g. with SIP, the SIP URI of the
   To header field is typically sufficient for targeting a live content,
   [9] is also typically sufficient for targeting a media object).

   It MUST include the RTSP Version in a "fmtp:rtsp version" parameter.

   It MAY include any necessary RTSP header field under the form of a
   "fmtp:rtsp h-*" parameter.

   It MAY indicate the association between the RTSP media stream and the
   media streams that are under its control (c.f.  Section 7).

   For each media stream controlled by the RTSP media stream, it MUST
   include an "a=recvonly" or "a=inactive" attribute.

4.2.  Offerer is an RTSP Server

   When an agent wishes to offer the role of an RTSP server, it has to
   perform the actions described in this section.

   It MUST offer a 'm' line for an RTSP stream (c.f.  Section 6).  It
   MUST also indicate that it will accept an incoming RTSP connection as
   defined in [6].  Typically, the port number is a port number of 554
   (rtsp server port) on its 'm' line, and the 'setup' attribute is set
   to 'passive'.

   It MUST either generate a new RTSP session or reuse an existing one,
   and add it in a "fmtp:rtsp h-session" attribute.

   It MUST include RTSP control attributes in a "control" parameter, as
   defined in [1] and [2].  If a "control" parameter contains a relative
   URI, a base URI must also be provided in a "fmtp rtsp h-content-base"
   or "fmtp rtsp h-content-location" attribute so that the RTSP client
   can construct an RTSP absolute request URI for its RTSP requests.




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   It MUST include the RTSP Version in a "fmtp:rtsp version" parameter.

   It MAY include any necessary RTSP header field under the form of a
   "fmtp:rtsp h-*" parameter.

   It MUST indicate the association between the RTSP media stream and
   the media streams that are under its control (c.f.  Section 7).

   For each media stream controlled by the RTSP media stream, it MUST
   also include an "a=sendonly" or "a=inactive" attribute.


5.  Procedure at the SDP Answerer

5.1.  Answerer is an RTSP Server

   When an agent both wishes to accept an offer from an RTSP client and
   to provide the role of an RTSP server, it has to perform the actions
   described in this section.

   It MUST offer a 'm' line for an RTSP stream (c.f.  Section 6).  It
   MUST also indicate that it accepts an incoming RTSP connection as
   defined in [6].  Typically, the port number is a port number of 554
   (rtsp server port) on its 'm' line, and the 'setup' attribute is set
   to 'passive'.

   It MUST either generate a new RTSP session if no one was provided in
   the offer, or reuse an existing RTSP session.  The RTSP session is
   added in the answer in a "fmtp:rtsp h-session" attribute.

   It MUST include RTSP control attributes in a "control" parameter, as
   defined in [1] and [2].  If a "control" parameter contains a relative
   URI, a base URI must also be provided in a "fmtp rtsp h-content-base"
   or "fmtp rtsp h-content-location" attribute so that the RTSP client
   can construct an RTSP absolute request URI for its RTSP requests.

   It MUST include the same "fmtp:rtsp version" attribute as received in
   the offer.

   It MAY include any other necessary RTSP header under the form of a
   "fmtp:rtsp h-*" parameter.

   It MUST indicate the association between the RTSP media stream and
   the media streams that are under its control (c.f.  Section 7).

   For each media stream controlled by the RTSP media stream, it MUST
   also include an "a=sendonly" or "a=inactive" attribute.




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5.2.  Answerer is an RTSP Client

   When an agent both wishes to accept an offer from an RTSP server and
   to provide the role of an RTSP client, it has to perform the actions
   described in this section.

   It MUST offer a 'm' line for an RTSP stream (c.f.  Section 6).  It
   MUST also indicate that it will initiate the outgoing connection for
   this stream as described in [6].  Typically, the port number should
   be a port number of 9 (the discard port) on its 'm' line, and the
   'setup' attribute is set to 'active'.

   It MUST add in the answer the same "fmtp:rtsp h-session" attribute as
   received in the offer.

   It MUST include in the offer the same "fmtp:rtsp version" attribute
   as received in the offer.

   It MAY include any necessary RTSP header field under the form of a
   "fmtp:rtsp h-*" parameter.

   It MUST indicate the association between the RTSP media stream and
   the media streams that are under its control (c.f.  Section 7).

   For each media stream controlled by the RTSP media stream, it MUST
   include an "a=recvonly" or "a=inactive" attribute.


6.  Fields in the 'm' Line

   This Section describes how to generate an 'm' line for an RTSP
   stream.

   According to the SDP specification [7], the 'm' line format is the
   following:

   m=<media> <port> <transport> <fmt> ...

   The media field MUST have a value of "application".

   The port field is set following the rules in [6].  Depending on the
   value of the 'setup' attribute, the port field contains the port the
   remote endpoint will initiate its TCP connection to, or is irrelevant
   (i.e., the endpoint will initiate the connection towards the remote
   endpoint) and should be set to a value of 9, which is the discard
   port.  In this specification RTSP only runs on top of TCP, therefore
   the port is always a TCP port.  A port field value of zero has the
   standard SDP meaning (i.e., rejection of the media stream).



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   This specification defines two new values for the transport field:
   TCP/RTSP and TCP/TLS/RTSP.  The former is used when RTSP runs
   directly on top of TCP and the latter is used when RTSP runs on top
   of TLS, which in turn runs on top of TCP.

   In order to have a fmt available for fmtp parameters dedicated to
   RTSP, this specification defines a new token, which value is "rtsp",
   that MUST be used in the fmt field.

   [[OPEN-ISSUE-2: can't we find a more elegant proposal than the "rtsp"
   token in the fmt field of the m-line?]]

   The following is an example of an 'm' line for an RTSP connection:

   m=application 554 TCP/RTSP rtsp


7.  RTSP Grouping of Media Lines

   This document defines an rtsp SDP media-level attribute.  Its
   Augmented BNF syntax is:

   rtsp-id-attribute = "a=rtspid"  [" m-stream:" token *(SP token)]

   The rtspid attribute is used in RTSP 'm' lines.  It defines an rtsp
   identifier and, possibly, associates it with one or more media
   streams.  The token representing the media stream is a pointer to the
   media stream, which is identified by an SDP label attribute [8]

   Endpoints which use the offer/answer model to establish RTSP
   connections MUST support the 'rtspid' and the 'label' attributes.  An
   RTSP server acting as an offerer or as an answerer SHOULD include
   these attributes in its session descriptions.


8.  Mapping of RTSP Parameters to SDP Attributes

   An RTSP parameter is included in "a=fmtp" line of SDP and is
   expressed in the form of parameter=value.

   a=fmtp:rtsp <parameter name>=<value>

   4 different format specific parameters are defined in this
   specification.







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8.1.  RTSP Version


   a=fmtp:rtsp version=<version-number>

   The "version" parameter sets the "version-number" representing the
   version of RTSP that will be used in the RTSP media stream.  The
   version number MUST either be "1.0" or "2.0".  The RTSP version MUST
   be included in all SDP offers and answers.  The same version MUST be
   used by both endpoints.

8.2.  RTSP Request-URI


   a=fmtp:rtsp uri=<request-uri>

   The "request-uri" sets the value of the RTSP URI that can be used by
   the client to target a specific presentation or media object in the
   RTSP server.  Typically, it is the counterpart of the Request-URI
   existing in a SETUP or DESCRIBE request.

8.3.  RTSP Header Attributes

   To exchange RTSP header fields within the SIP offer/answer, the RTSP
   media stream allows for attributes with the following format:

   a=fmtp:rtsp h-<header-name>=<header-value>

   where "header-name" is the name of the RTSP header field being
   described and "header-value" is the value of the RTSP header field.

   The value of the header-name is case insensitive.  The value of the
   header-value is interpreted according to the rules of RTSP.

   [[OPEN-ISSUE-3: This point is similar to OPEN-ISSUE-1.  Do we allow
   to transport any RTSP necessary header within SDP or do we restrict
   the list to some really few RTSP headers?]]

8.4.  RTSP Vendor Specific Attributes

   Attributes specific to RTSP vendors can be used under the following
   format:

   a=fmtp:rtsp v-<vendor-id>=<vendor-param>

   where





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   o  vendor-id is a globally unique vendor-identifier (the vendor's SMI
      network management private enterprise code) See [RFC 1700].
   o  vendor-param is an alpha numeric parameter name, optionally
      followed by a ":" and a parameter value.
   So for example, if Kasenna (vendor-id: 6293) wanted to convey a
   vendor specific attribute named foo with a value of "bar 1234", it
   would be encoded as follows:

   a=fmtp:rtsp v-6293:foo:bar 1234


9.  Examples

   The following is an example of an offer sent by an agent, 'Alice',
   using SIP to establish the session and using an RTSP client for
   playing media streams.  During the session Alice switches the session
   mode to a conversational mode with an updated SDP.  In the case of
   SIP being used to establish the session, this new SDP will be
   encapsulated in a re INVITE with the original session establishment
   dialog.


  v=0
  o=alice 2890844526 2890844526 IN IP4 a.atlanta.example.com
  s=Streaming Session
  i=A Streaming session declared within the session description protocol
  c=IN IP4 a.atlanta.example.com
  t=0 0
  m=application 9 TCP/RTSP rtsp
  a=fmtp:rtsp request-uri: rtsp://b.biloxi.example.com/scene
  a=fmtp:rtsp version: 2.0
  a=fmtp:rtsp h-accept-ranges: NPT
  a=connection:new
  a=setup:active
  a=rtspid m-stream:10
  m=audio 6666 RTP/AVP 0
  a=rtpmap:0 PCMU/8000
  a=recvonly
  a=label:10

   The following is the answer returned by the client.










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  v=0
  o=bob 2808844564 2808844564 IN IP4 b.biloxi.example.com
  s=Streaming Session
  i=A Streaming session declared within the session description protocol
  c=IN IP4 b.biloxi.example.com
  t=0 0
  m=application 554 TCP/RTSP rtsp
  a=connection:new
  a=setup:passive
  a=control: rtsp://b.biloxi.example.com/scene
  a=fmtp:rtsp version: 2.0
  a=fmtp:rtsp h-accept-ranges: NPT
  a=fmtp:rtsp h-session: 6238237
  a=fmtp:rtsp h-date: Tue, 05 Sep 2006 09:56:44 GMT
  a=fmtp:rtsp h-rtp-info: url="rtsp://b.biloxi.example.com/scene"
                          ssrc=1631654733:seq=53961;rtptime=0
  a=rtspid m-stream:10
  m=audio 8888 RTP/AVP 0
  a=rtpmap:0 PCMU/8000
  a=sendonly
  a=label:10

   Some time later, a new offer is sent to switch to a conversational
   mode.  The port field of the RTSP media stream is set to zero, and
   the audio media stream is set to "sendrecv"


  v=0
  o=alice 2890844526 2890844527 IN IP4 a.atlanta.example.com
  s=Streaming Session
  i=A Streaming session declared within the session description protocol
  c=IN IP4 a.atlanta.example.com
  t=0 0
  m=application 0 TCP/RTSP rtsp
  a=rtspid m-stream:10
  m=audio 6666 RTP/AVP 0
  a=rtpmap:0 PCMU/8000
  a=sendrecv
  a=label:10

   The following is the answer returned by the client.










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  v=0
  o=bob 2808844564 2808844565 IN IP4 b.biloxi.example.com
  s=Streaming Session
  i=A Streaming session declared within the session description protocol
  c=IN IP4 b.biloxi.example.com
  t=0 0
  m=application 0 TCP/RTSP rtsp
  a=rtspid m-stream:10
  m=audio 8888 RTP/AVP 0
  a=rtpmap:0 PCMU/8000
  a=sendrecv
  a=label:10


10.  Security Considerations

   T.B.D.


11.  IANA Considerations

11.1.  Registration of the 'TCP/RTSP' and 'TCL/TLS/RTSP' SDP 'Proto'

   This section instructs the IANA to register the following two new
   values for the SDP 'proto' field under the Session Description
   Protocol (SDP) Parameters registry:

                          +--------------+-----------+
                          | Value        | Reference |
                          +--------------+-----------+
                          | TCP/RTSP     |  RFCxxxx  |
                          | TCP/TLS/RTSP |  RFCxxxx  |
                          +--------------+-----------+

                      Table 1: Values for the SDP 'proto' field

   [Note to the RFC editor: please, replace RFCxxxx with the RFC number
   that this document will be assigned.]

11.2.  Registration of the SDP 'rtspid' Attribute

   This section instructs the IANA to register the following SDP att-
   field under the Session Description Protocol (SDP) Parameters
   registry:

   Contact name: xavier.marjou@orange-ft.com

   Attribute name: rtspid



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   Long-form attribute name: RTSP Identifier

   Type of attribute Media level

   Subject to charset: No

   Purpose of attribute: The 'rtspid' attribute associates an RTSP media
   stream with one or more media streams.

   Allowed attribute values: Tokens


12.  Acknowledgements

   TBD.


13.  References

13.2.  Normative References

   [1]  Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time Streaming
        Protocol (RTSP)", RFC 2326, April 1998.

   [2]  Schulzrinne, H., Rao, A., Lanphier, R., Westerlund, M., and A.
        Narasimhan, "Real Time Streaming Protocol 2.0 (RTSP)",
        draft-ietf-mmusic-rfc2326bis-13.txt (work in progress),
        October 2005.

   [3]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
        the Session Description Protocol (SDP)", RFC 3264, June 2002.

   [4]  Whitehead, S., Montpetit, M., and X. Marjou, "An Evaluation of
        Session Initiation Protocol (SIP) for use in Streaming  Media
        Applications", draft-whitehead-mmusic-sip-for-streaming-media-01
        (work in progress), June 2006.

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

   [6]  Yon, D. and G. Camarillo, "TCP-Based Media Transport in the
        Session Description Protocol (SDP)", RFC 4145, September 2005.

   [7]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
        Description Protocol", RFC 4566, July 2006.

   [8]  Levin, O. and G. Camarillo, "The Session Description Protocol
        (SDP) Label Attribute", RFC 4574, August 2006.



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13.3.  Informational References

   [9]  Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network Media
        Services with SIP", RFC 4240, December 2005.

13.  References


Appendix A.  A SIP-RTSP call-flow example

   [[NOTE: This section shows a session where Alice is doing trick
   plays.  This example appears only for early illustrative purposes and
   will be removed in the next version of this document]]

  INVITE sip:bob@biloxi.example.com SIP/2.0
  Via: SIP/2.0/UDP a.atlanta.example.com;branch=z9hG4bK74bf9
  Max-Forwards: 70
  From: <sip:alice@atlanta.example.com>;tag=9fxced76sl
  To: <sip:bob@biloxi.example.com>
  Call-ID: a84b4c76e66711@a.atlanta.example.com
  CSeq: 1 INVITE
  Accept: application/sdp
  Contact: <sip:alice@a.atlanta.example.com>
  Content-Type: application/sdp
  Content-Length: 338

  v=0
  o=alice 2155025512 2155025512 IN IP4 a.atlanta.example.com
  s=Streaming Session
  i=A Streaming session declared within the session description protocol
  c=IN IP4 a.atlanta.example.com
  t=0 0
  m=application 9 TCP/RTSP rtsp
  a=connection:new
  a=setup:active
  a=rtsp version: 2.0
  a=rtsp h-accept-ranges: NPT
  a=rtspid m-stream:10
  m=video 8888 RTP/AVP 26
  a=recvonly
  a=label:10


  SIP/2.0 100 Trying
  Via: SIP/2.0/UDP a.atlanta.example.com;branch=z9hG4bK74bf9
  From: <sip:alice@atlanta.example.com>;tag=9fxced76sl
  To: <sip:bob@biloxi.example.com>;tag=8321234356
  Call-ID: a84b4c76e66711@a.atlanta.example.com



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  CSeq: 1 INVITE
  Content-Length: 0


  SIP/2.0 200 OK
  Via: SIP/2.0/UDP a.atlanta.example.com;branch=z9hG4bK74bf9
  From: <sip:alice@atlanta.example.com>;tag=9fxced76sl
  To: <sip:bob@biloxi.example.com>;tag=8321234356
  Call-ID: a84b4c76e66711@a.atlanta.example.com
  CSeq: 1 INVITE
  Contact: <sip:bob@b.biloxi.example.com>
  Content-Type: application/sdp
  Content-Length: 147

  v=0
  o=bob 2890844527 2890844527 IN IP4 b.biloxi.example.com
  s=Streaming Session
  i=A Streaming session declared within the session description protocol
  c=IN IP4 b.biloxi.example.com
  t=0 0
  m=application 554 TCP/RTSP rtsp
  a=connection:new
  a=setup:passive
  a=control: rtsp://b.biloxi.example.com/scene
  a=rtsp version: 2.0
  a=rtsp h-accept-ranges: NPT
  a=rtsp h-session: 6238237
  a=rtsp h-date: Tue, 05 Sep 2006 09:56:44 GMT
  a=rtsp h-rtp-info: url="rtsp://b.biloxi.example.com/scene"
                     ssrc=1631654733:seq=53961;rtptime=0
  a=rtspid m-stream:10
  m=video 6666 RTP/AVP 26
  a=sendonly
  a=label:10


  ACK sip:bob@b.biloxi.example.com SIP/2.0
  Via: SIP/2.0/UDP a.atlanta.example.com;branch=z9hG4bK74bd5
  Max-Forwards: 70
  From: <sip:alice@atlanta.example.com>;tag=9fxced76sl
  To: <sip:bob@biloxi.example.com>5060>;tag=8321234356
  Call-ID: a84b4c76e66711@a.atlanta.example.com
  CSeq: 1 ACK
  Content-Length: 0


  PLAY rtsp://b.biloxi.example.com/scene RTSP/2.0
  CSeq: 1



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  Session: 6238237
  Scale: 1
  Range: npt=now-
  User-Agent: foobar


  RTSP/2.0 200 OK
  CSeq: 1
  Session: 6238237
  Range: npt=now-
  Date: Tue, 05 Sep 2006 09:56:45 GMT
  RTP-Info: url="rtsp://b.biloxi.example.com/scene"
            ssrc=1631654733:seq=53961;rtptime=0
  Server: barfoo


  PAUSE rtsp://b.biloxi.example.com/scene RTSP/2.0
  CSeq: 2
  Session: 6238237
  Scale: 0
  User-Agent: foobar


  RTSP/2.0 200 OK
  CSeq: 2
  Session: 6238237
  Range:12-
  Date: Tue, 05 Sep 2006 09:56:50 GMT


  PLAY rtsp://b.biloxi.example.com/scene RTSP/2.0
  CSeq: 3
  Session: 6238237
  Scale: -1
  User-Agent: foobar


  RTSP/2.0 200 OK
  CSeq: 3
  Session: 6238237
  Range: npt=now-
  Date: Tue, 05 Sep 2006 09:56:55 GMT
  RTP-Info: url="rtsp://b.biloxi.example.com/scene"
            ssrc=1631654733:seq=54024;rtptime=1080000
  Server: barfoo


  BYE sip:bob@b.biloxi.example.com SIP/2.0



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  Via: SIP/2.0/UDP a.atlanta.example.com;branch=z9hG4bK74bd6
  Max-Forwards: 70
  From: <sip:alice@atlanta.example.com>;tag=9fxced76sl
  To: <sip:bob@biloxi.example.com>;tag=8321234356
  Call-ID: a84b4c76e66711@a.atlanta.example.com
  CSeq: 2 BYE
  Content-Length: 0


  SIP/2.0 200 OK
  Via: SIP/2.0/UDP a.atlanta.example.com;branch=z9hG4bK74bd6
  From: <sip:alice@atlanta.example.com>;tag=9fxced76sl
  To: <sip:bob@biloxi.example.com>;tag=8321234356
  Call-ID: a84b4c76e66711@a.atlanta.example.com
  CSeq: 2 BYE
  Content-Length: 0


Authors' Addresses

   Xavier Marjou
   France Telecom
   2, rue Pierre Marzin
   Lannion, Brittany  22307
   France

   Email: xavier.marjou@orange-ft.com


   Steven Whitehead
   Verizon
   40 Sylvan Road
   Waltham, MA  02451
   USA

   Email: steven.d.whitehead@verizon.com


   Marie-Jose Montpetit
   Motorola
   55 Hayden Avenue, 1st floor
   Lexington, MA  02421
   USA

   Email: mmontpetit@motorola.com






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   Sam Ganesan
   Motorola
   55 Hayden Avenue, 1st floor
   Lexington, MA  02421
   USA

   Email: sam.ganesan@motorola.com


   David Ress
   Nortel

   Email: dress@nortel.com


   Dominic Goodwill
   Nortel

   Email: goodwill@nortel.com


Full Copyright Statement

   Copyright (C) The Internet Society (2006).

   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.

   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.


Intellectual Property

   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.



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   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.


Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.

































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