draft-ietf-sipping-transc-framework-05.txt   rfc5369.txt 
SIPPING Working Group G. Camarillo
Internet-Draft Ericsson
Expires: June 3, 2007 November 30, 2006
Framework for Transcoding with the Session Initiation Protocol (SIP)
draft-ietf-sipping-transc-framework-05.txt
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http://www.ietf.org/shadow.html. Request for Comments: 5369 Ericsson
Category: Informational October 2008
This Internet-Draft will expire on June 3, 2007. Framework for Transcoding with the Session Initiation Protocol (SIP)
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Copyright (C) The Internet Society (2006). This memo provides information for the Internet community. It does
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memo is unlimited.
Abstract Abstract
This document defines a framework for transcoding with SIP. This This document defines a framework for transcoding with SIP. This
framework includes how to discover the need for transcoding services framework includes how to discover the need for transcoding services
in a session and how to invoke those transcoding services. Two in a session and how to invoke those transcoding services. Two
models for transcoding services invocation are discussed: the models for transcoding services invocation are discussed: the
conference bridge model and the third party call control model. Both conference bridge model and the third-party call control model. Both
models meet the requirements for SIP regarding transcoding services models meet the requirements for SIP regarding transcoding services
invocation to support deaf, hard of hearing, and speech-impaired invocation to support deaf, hard of hearing, and speech-impaired
individuals. individuals.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Discovery of the Need for Transcoding Services . . . . . . . . 3 2. Discovery of the Need for Transcoding Services . . . . . . . . 2
3. Transcoding Services Invocation . . . . . . . . . . . . . . . 4 3. Transcoding Services Invocation . . . . . . . . . . . . . . . . 4
3.1. Third Party Call Control Transcoding Model . . . . . . . . 5 3.1. Third-Party Call Control Transcoding Model . . . . . . . . 4
3.2. Conference Bridge Transcoding Model . . . . . . . . . . . 6 3.2. Conference Bridge Transcoding Model . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Normative References . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 12
1. Introduction 1. Introduction
Two user agents involved in a SIP [3] dialog may find it impossible Two user agents involved in a SIP [RFC3261] dialog may find it
to establish a media session due to a variety of incompatibilities. impossible to establish a media session due to a variety of
Assuming that both user agents understand the same session incompatibilities. Assuming that both user agents understand the
description format (e.g., SDP [12]), incompatibilities can be found same session description format (e.g., SDP [RFC4566]),
at the user agent level and at the user level. At the user agent incompatibilities can be found at the user agent level and at the
level, both terminals may not support any common codec or may not user level. At the user agent level, both terminals may not support
support common media types (e.g., a text-only terminal and an audio- any common codec or may not support common media types (e.g., a text-
only terminal). At the user level, a deaf person will not understand only terminal and an audio-only terminal). At the user level, a deaf
anything said over an audio stream. person will not understand anything said over an audio stream.
In order to make communications possible in the presence of In order to make communications possible in the presence of
incompatibilities, user agents need to introduce intermediaries that incompatibilities, user agents need to introduce intermediaries that
provide transcoding services to a session. From the SIP point of provide transcoding services to a session. From the SIP point of
view, the introduction of a transcoder is done in the same way to view, the introduction of a transcoder is done in the same way to
resolve both user level and user agent level incompatibilities. So, resolve both user level and user agent level incompatibilities. So,
the invocation mechanisms described in this document are generally the invocation mechanisms described in this document are generally
applicable to any type of incompatibility related to how the applicable to any type of incompatibility related to how the
information that needs to be communicated is encoded. information that needs to be communicated is encoded.
Furthermore, although this framework focuses on transcoding, the Furthermore, although this framework focuses on transcoding, the
mechanisms described are applicable to media manipulation in mechanisms described are applicable to media manipulation in
general. It would be possible to use them, for example, to invoke general. It would be possible to use them, for example, to invoke
a server that simply increased the volume of an audio stream. a server that simply increases the volume of an audio stream.
This document does not describe media server discovery. That is an This document does not describe media server discovery. That is an
orthogonal problem that one can address using user agent provisioning orthogonal problem that one can address using user agent provisioning
or other methods. or other methods.
The remainder of this document is organized as follows. Section 2 The remainder of this document is organized as follows. Section 2
deals with the discovery of the need for transcoding services for a deals with the discovery of the need for transcoding services for a
particular session. Section 3 introduces the third party call particular session. Section 3 introduces the third-party call
control and conference bridge transcoding invocation models, which control and conference bridge transcoding invocation models, which
are further described in Section 3.1 and Section 3.2 respectively. are further described in Sections 3.1 and 3.2, respectively. Both
Both models meet the requirements regarding transcoding services models meet the requirements regarding transcoding services
invocation in RFC3351 [6] to support deaf, hard of hearing, and invocation in RFC 3351 [RFC3351], which support deaf, hard of
speech-impaired individuals. hearing, and speech-impaired individuals.
2. Discovery of the Need for Transcoding Services 2. Discovery of the Need for Transcoding Services
According to the one-party consent model defined in RFC 3238 [2], According to the one-party consent model defined in RFC 3238
services that involve media manipulation invocation are best invoked [RFC3238], services that involve media manipulation invocation are
by one of the end-points involved in the communication, as opposed to best invoked by one of the endpoints involved in the communication,
being invoked by an intermediary in the network. Following this as opposed to being invoked by an intermediary in the network.
principle, one of the end-points should be the one detecting that Following this principle, one of the endpoints should be the one
transcoding is needed for a particular session. detecting that transcoding is needed for a particular session.
In order to decide whether or not transcoding is needed, a user agent In order to decide whether or not transcoding is needed, a user agent
needs to know the capabilities of the remote user agent. A user needs to know the capabilities of the remote user agent. A user
agent acting as an offerer [4] typically obtains this knowledge by agent acting as an offerer [RFC3264] typically obtains this knowledge
downloading a presence document that includes media capabilities by downloading a presence document that includes media capabilities
(e.g., Bob is available on a terminal that only supports audio) or by (e.g., Bob is available on a terminal that only supports audio) or by
getting an SDP description of media capabilities as defined in RFC getting an SDP description of media capabilities as defined in RFC
3264 [4]. 3264 [RFC3264].
Presence documents are typically received in a NOTIFY [5] request as Presence documents are typically received in a NOTIFY request
a result of a subscription. SDP media capabilities descriptions are [RFC3265] as a result of a subscription. SDP media capabilities
typically received in a 200 (OK) response to an OPTIONS request or in descriptions are typically received in a 200 (OK) response to an
a 488 (Not Acceptable Here) response to an INVITE. OPTIONS request or in a 488 (Not Acceptable Here) response to an
INVITE.
In the absence of presence information, routing logic that involves In the absence of presence information, routing logic that involves
parallel forking to several user agents may make it difficult (or parallel forking to several user agents may make it difficult (or
impossible) for the caller to know which user agent will answer the impossible) for the caller to know which user agent will answer the
next call attempt. For example, a call attempt may reach the user's next call attempt. For example, a call attempt may reach the user's
voice mail while the next one may reach a SIP phone where the user is voice mail while the next one may reach a SIP phone where the user is
available. If both terminating user agents have different available. If both terminating user agents have different
capabilities, the caller cannot know, even after the first call capabilities, the caller cannot know, even after the first call
attempt, whether or not transcoding will be necessary for the attempt, whether or not transcoding will be necessary for the
session. This is a well-known SIP problem that is referred to as session. This is a well-known SIP problem that is referred to as
skipping to change at page 4, line 38 skipping to change at page 3, line 39
HERFP is outside the scope of this document. HERFP is outside the scope of this document.
It is recommended that an offerer does not invoke transcoding It is recommended that an offerer does not invoke transcoding
services before making sure that the answerer does not support the services before making sure that the answerer does not support the
capabilities needed for the session. Making wrong assumptions about capabilities needed for the session. Making wrong assumptions about
the answerer's capabilities can lead to situations where two the answerer's capabilities can lead to situations where two
transcoders are introduced (one by the offerer and one by the transcoders are introduced (one by the offerer and one by the
answerer) in a session that would not need any transcoding services answerer) in a session that would not need any transcoding services
at all. at all.
An example of the situation above is a call between two GSM phones An example of the situation above is a call between two GSM
(without using transcoding-free operation). Both phones use a GSM (Global System for Mobile Communications) phones (without using
codec, but the speech is converted from GSM to PCM by the transcoding-free operation). Both phones use a GSM codec, but the
speech is converted from GSM to PCM (Pulse Code Modulation) by the
originating MSC (Mobile Switching Center) and from PCM back to GSM originating MSC (Mobile Switching Center) and from PCM back to GSM
by the terminating MSC. by the terminating MSC.
Note that transcoding services can be symmetric (e.g., speech-to-text Note that transcoding services can be symmetric (e.g., speech-to-text
plus text-to-speech) or asymmetric (e.g., a one-way speech-to-text plus text-to-speech) or asymmetric (e.g., a one-way speech-to-text
transcoding for a hearing-impaired user that can talk). transcoding for a hearing-impaired user that can talk).
3. Transcoding Services Invocation 3. Transcoding Services Invocation
Once the need for transcoding for a particular session has been Once the need for transcoding for a particular session has been
skipping to change at page 5, line 15 skipping to change at page 4, line 20
As stated earlier, transcoder location is outside the scope of this As stated earlier, transcoder location is outside the scope of this
document. So, we assume that the user agent invoking transcoding document. So, we assume that the user agent invoking transcoding
services knows the URI of a server that provides them. services knows the URI of a server that provides them.
Invoking transcoding services from a server (T) for a session between Invoking transcoding services from a server (T) for a session between
two user agents (A and B) involves establishing two media sessions; two user agents (A and B) involves establishing two media sessions;
one between A and T and another between T and B. How to invoke T's one between A and T and another between T and B. How to invoke T's
services (i.e., how to establish both A-T and T-B sessions) depends services (i.e., how to establish both A-T and T-B sessions) depends
on how we model the transcoding service. We have considered two on how we model the transcoding service. We have considered two
models for invoking a transcoding service. The first is to use third models for invoking a transcoding service. The first is to use
party call control [7], also referred to as 3pcc. The second is to third-party call control [RFC3725], also referred to as 3pcc. The
use a (dial-in and dial-out) conference bridge that negotiates the second is to use a (dial-in and dial-out) conference bridge that
appropriate media parameters on each individual leg (i.e., A-T and negotiates the appropriate media parameters on each individual leg
T-B). (i.e., A-T and T-B).
Section 3.1 analyzes the applicability of the third party call Section 3.1 analyzes the applicability of the third-party call
control model and Section 3.2 analyzes the applicability of the control model, and Section 3.2 analyzes the applicability of the
conference bridge transcoding invocation model. conference bridge transcoding invocation model.
3.1. Third Party Call Control Transcoding Model 3.1. Third-Party Call Control Transcoding Model
In the 3pcc transcoding model, defined in [10], the user agent In the 3pcc transcoding model, defined in [RFC4117], the user agent
invoking the transcoding service has a signalling relationship with invoking the transcoding service has a signalling relationship with
the transcoder and another signalling relationship with the remote the transcoder and another signalling relationship with the remote
user agent. There is no signalling relationship between the user agent. There is no signalling relationship between the
transcoder and the remote user agent, as shown in Figure 1. transcoder and the remote user agent, as shown in Figure 1.
+-------+ +-------+
| | | |
| T |** | T |**
| | ** | | **
+-------+ ** +-------+ **
skipping to change at page 6, line 26 skipping to change at page 5, line 26
v * ** v * **
+-------+ +-------+ +-------+ +-------+
| | | | | | | |
| A |<-----SIP----->| B | | A |<-----SIP----->| B |
| | | | | | | |
+-------+ +-------+ +-------+ +-------+
<-SIP-> Signalling <-SIP-> Signalling
******* Media ******* Media
Figure 1: Third party call control model Figure 1: Third-Party Call Control Model
This model is suitable for advanced endpoints that are able to This model is suitable for advanced endpoints that are able to
perform third party call control. It allows end-points to invoke perform third party call control. It allows endpoints to invoke
transcoding services on a stream basis. That is, the media streams transcoding services on a stream basis. That is, the media streams
that need transcoding are routed through the transcoder while the that need transcoding are routed through the transcoder while the
streams that do not need it are sent directly between the endpoints. streams that do not need it are sent directly between the endpoints.
This model also allows to invoke one transcoder for the sending This model also allows invoking one transcoder for the sending
direction and a different one for the receiving direction of the same direction and a different one for the receiving direction of the same
stream. stream.
Invoking a transcoder in the middle of an ongoing session is also Invoking a transcoder in the middle of an ongoing session is also
quite simple. This is useful when session changes occur (e.g., an quite simple. This is useful when session changes occur (e.g., an
audio session is upgraded to an audio/video session) and the end- audio session is upgraded to an audio/video session) and the
points cannot cope with the changes (e.g., they had common audio endpoints cannot cope with the changes (e.g., they had common audio
codecs but no common video codecs). codecs but no common video codecs).
The privacy level that is achieved using 3pcc is high, since the The privacy level that is achieved using 3pcc is high, since the
transcoder does not see the signalling between both end-points. In transcoder does not see the signalling between both endpoints. In
this model, the transcoder only has access to the information that is this model, the transcoder only has access to the information that is
strictly needed to perform its function. strictly needed to perform its function.
3.2. Conference Bridge Transcoding Model 3.2. Conference Bridge Transcoding Model
In a centralized conference, there are a number of media streams In a centralized conference, there are a number of media streams
between the conference server and each participant of a conference. between the conference server and each participant of a conference.
For a given media type (e.g., audio) the conference server sends, For a given media type (e.g., audio) the conference server sends,
over each individual stream, the media received over the rest of the over each individual stream, the media received over the rest of the
streams, typically performing some mixing. If the capabilities of streams, typically performing some mixing. If the capabilities of
all the endpoints participating in the conference are not the same, all the endpoints participating in the conference are not the same,
the conference server may have to send audio to different the conference server may have to send audio to different
participants using different audio codecs. participants using different audio codecs.
Consequently, we can model a transcoding service as a two-party Consequently, we can model a transcoding service as a two-party
conference server that may change not only the codec in use, but also conference server that may change not only the codec in use, but also
the format of the media (e.g., audio to text). the format of the media (e.g., audio to text).
skipping to change at page 7, line 17 skipping to change at page 6, line 15
streams, typically performing some mixing. If the capabilities of streams, typically performing some mixing. If the capabilities of
all the endpoints participating in the conference are not the same, all the endpoints participating in the conference are not the same,
the conference server may have to send audio to different the conference server may have to send audio to different
participants using different audio codecs. participants using different audio codecs.
Consequently, we can model a transcoding service as a two-party Consequently, we can model a transcoding service as a two-party
conference server that may change not only the codec in use, but also conference server that may change not only the codec in use, but also
the format of the media (e.g., audio to text). the format of the media (e.g., audio to text).
Using this model, T behaves as a B2BUA (Back-to-Back User Agent) and Using this model, T behaves as a B2BUA (Back-to-Back User Agent) and
the whole A-T-B session is established as described in [11]. the whole A-T-B session is established as described in [RFC5370].
Figure 2 shows the signalling relationships between the end-points Figure 2 shows the signalling relationships between the endpoints and
and the transcoder. the transcoder.
+-------+ +-------+
| |** | |**
| T | ** | T | **
| |\ ** | |\ **
+-------+ \\ ** +-------+ \\ **
^ * \\ ** ^ * \\ **
| * \\ ** | * \\ **
| * SIP ** | * SIP **
SIP * \\ ** SIP * \\ **
skipping to change at page 7, line 42 skipping to change at page 6, line 40
v * \ ** v * \ **
+-------+ +-------+ +-------+ +-------+
| | | | | | | |
| A | | B | | A | | B |
| | | | | | | |
+-------+ +-------+ +-------+ +-------+
<-SIP-> Signalling <-SIP-> Signalling
******* Media ******* Media
Figure 2: Conference bridge model Figure 2: Conference Bridge Model
In the conferencing bridge model, the end-point invoking the In the conferencing bridge model, the endpoint invoking the
transcoder is generally involved in less signalling exchanges than in transcoder is generally involved in less signalling exchanges than in
the 3pcc model. This may be an important feature for end-points the 3pcc model. This may be an important feature for endpoints using
using low bandwidth or high-delay access links (e.g., some wireless low-bandwidth or high-delay access links (e.g., some wireless
accesses). accesses).
On the other hand, this model is less flexible than the 3pcc model. On the other hand, this model is less flexible than the 3pcc model.
It is not possible to use different transcoders for different streams It is not possible to use different transcoders for different streams
or for different directions of a stream. or for different directions of a stream.
Invoking a transcoder in the middle of an ongoing session or changing Invoking a transcoder in the middle of an ongoing session or changing
from one transcoder to another requires the remote end-point to from one transcoder to another requires the remote endpoint to
support the Replaces [9] extension. At present, not many user agents support the Replaces [RFC3891] extension. At present, not many user
support it. agents support it.
Simple end-points that cannot perform 3pcc and thus cannot use the Simple endpoints that cannot perform 3pcc and thus cannot use the
3pcc model, of course, need to use the conference bridge model. 3pcc model, of course, need to use the conference bridge model.
4. Security Considerations 4. Security Considerations
The specifications of the 3pcc and the conferencing transcoding The specifications of the 3pcc and the conferencing transcoding
models discuss security issues directly related to the implementation models discuss security issues directly related to the implementation
of those models. Additionally, there are some considerations that of those models. Additionally, there are some considerations that
apply to transcoding in general. apply to transcoding in general.
In a session, a transcoder has access to at least some of the media In a session, a transcoder has access to at least some of the media
exchanged between the endpoints. In order to avoid rogue transcoders exchanged between the endpoints. In order to avoid rogue transcoders
getting access to those media, it is recommended that endpoints getting access to those media, it is recommended that endpoints
authenticate the transcoder. TLS [1] and S/MIME [8] can be used for authenticate the transcoder. TLS [RFC5246] and S/MIME [RFC3850] can
this purpose. be used for this purpose.
To achieve a higher degree of privacy, endpoints following the 3pcc To achieve a higher degree of privacy, endpoints following the 3pcc
transcoding model can use one transcoder in one direction and a transcoding model can use one transcoder in one direction and a
different one in the other direction. This way, no single transcoder different one in the other direction. This way, no single transcoder
has access to all the media exchanged between the endpoints. has access to all the media exchanged between the endpoints.
The fact that transcoders need to access media exchanged between the The fact that transcoders need to access media exchanged between the
endpoints implies that endpoints cannot use end-to-end media security endpoints implies that endpoints cannot use end-to-end media security
mechanisms. Media encryption would not allow the transcoder to mechanisms. Media encryption would not allow the transcoder to
access the media and media integrity protection would not allow the access the media, and media integrity protection would not allow the
transcoder to modify the media (which is obviously necessary to transcoder to modify the media (which is obviously necessary to
perform the transcoding function). Nevertheless, endpoints can still perform the transcoding function). Nevertheless, endpoints can still
use media security between the transcoder and themselves. use media security between the transcoder and themselves.
5. IANA Considerations 5. Contributors
This document does not contain any IANA actions.
6. Contributors
This document is the result of discussions amongst the conferencing This document is the result of discussions amongst the conferencing
design team. The members of this team include Eric Burger, Henning design team. The members of this team include Eric Burger, Henning
Schulzrinne and Arnoud van Wijk. Schulzrinne, and Arnoud van Wijk.
7. References 6. References
7.1. Normative References 6.1. Normative References
[1] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", [RFC3238] Floyd, S. and L. Daigle, "IAB Architectural and Policy
RFC 2246, January 1999. Considerations for Open Pluggable Edge Services",
RFC 3238, January 2002.
[2] Floyd, S. and L. Daigle, "IAB Architectural and Policy [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
Considerations for Open Pluggable Edge Services", RFC 3238, A., Peterson, J., Sparks, R., Handley, M., and E.
January 2002. Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: with Session Description Protocol (SDP)", RFC 3264,
Session Initiation Protocol", RFC 3261, June 2002. June 2002.
[4] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with [RFC3265] Roach, A.B., "Session Initiation Protocol (SIP)-Specific
Session Description Protocol (SDP)", RFC 3264, June 2002. Event Notification", RFC 3265, June 2002.
[5] Roach, A., "Session Initiation Protocol (SIP)-Specific Event [RFC3351] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A.
Notification", RFC 3265, June 2002. van Wijk, "User Requirements for the Session Initiation
Protocol (SIP) in Support of Deaf, Hard of Hearing and
Speech-impaired Individuals", RFC 3351, August 2002.
[6] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. van [RFC3725] Rosenberg, J., Peterson, J., Schulzrinne, H., and G.
Wijk, "User Requirements for the Session Initiation Protocol Camarillo, "Best Current Practices for Third Party Call
(SIP) in Support of Deaf, Hard of Hearing and Speech-impaired Control (3pcc) in the Session Initiation Protocol (SIP)",
Individuals", RFC 3351, August 2002. BCP 85, RFC 3725, April 2004.
[7] Rosenberg, J., Peterson, J., Schulzrinne, H., and G. Camarillo, [RFC3850] Ramsdell, B., "Secure/Multipurpose Internet Mail
"Best Current Practices for Third Party Call Control (3pcc) in Extensions (S/MIME) Version 3.1 Certificate Handling",
the Session Initiation Protocol (SIP)", BCP 85, RFC 3725, RFC 3850, July 2004.
April 2004.
[8] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions [RFC3891] Mahy, R., Biggs, B., and R. Dean, "The Session Initiation
(S/MIME) Version 3.1 Certificate Handling", RFC 3850, Protocol (SIP) "Replaces" Header", RFC 3891,
July 2004. September 2004.
[9] Mahy, R., Biggs, B., and R. Dean, "The Session Initiation [RFC4117] Camarillo, G., Burger, E., Schulzrinne, H., and A. van
Protocol (SIP) "Replaces" Header", RFC 3891, September 2004. Wijk, "Transcoding Services Invocation in the Session
Initiation Protocol (SIP) Using Third Party Call Control
(3pcc)", RFC 4117, June 2005.
[10] Camarillo, G., Burger, E., Schulzrinne, H., and A. van Wijk, [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
"Transcoding Services Invocation in the Session Initiation (TLS) Protocol Version 1.2", RFC 5246, August 2008.
Protocol (SIP) Using Third Party Call Control (3pcc)",
RFC 4117, June 2005.
[11] Camarillo, G., "The Session Initiation Protocol (SIP) [RFC5370] Camarillo, G., "The Session Initiation Protocol (SIP)
Conference Bridge Transcoding Model", Conference Bridge Transcoding Model", RFC 5370,
draft-ietf-sipping-transc-conf-03 (work in progress), October 2008.
June 2006.
7.2. Informative References 6.2. Informative References
[12] Handley, M., "SDP: Session Description Protocol", [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
draft-ietf-mmusic-sdp-new-26 (work in progress), January 2006. Description Protocol", RFC 4566, July 2006.
Author's Address Author's Address
Gonzalo Camarillo Gonzalo Camarillo
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
Jorvas 02420 Jorvas 02420
Finland Finland
Email: Gonzalo.Camarillo@ericsson.com EMail: Gonzalo.Camarillo@ericsson.com
Intellectual Property Statement Full Copyright Statement
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made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
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attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
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specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
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ietf-ipr@ietf.org. ietf-ipr@ietf.org.
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This document and the information contained herein are provided on an
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ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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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.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
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