draft-ietf-sipping-transc-3pcc-01.txt   draft-ietf-sipping-transc-3pcc-02.txt 
Internet Engineering Task Force SIP WG Internet Engineering Task Force SIP WG
Internet Draft G. Camarillo Internet Draft G. Camarillo
Ericsson Ericsson
E. Burger E. Burger
Brooktrout Brooktrout
H. Schulzrinne H. Schulzrinne
Columbia University Columbia University
A. van Wijk A. van Wijk
Viataal Viataal
draft-ietf-sipping-transc-3pcc-01.txt draft-ietf-sipping-transc-3pcc-02.txt
June 7, 2004 September 17, 2004
Expires: December, 2004 Expires: March, 2005
Transcoding Services Invocation in the Session Initiation Transcoding Services Invocation in the Session Initiation
Protocol (SIP) Using Third Party Call Control (3pcc) Protocol (SIP) Using Third Party Call Control (3pcc)
STATUS OF THIS MEMO STATUS OF THIS MEMO
By submitting this Internet-Draft, I certify that any applicable By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed, patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance with and any of which I become aware will be disclosed, in accordance with
RFC 3668. RFC 3668.
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1 Introduction ........................................ 3 1 Introduction ........................................ 3
2 General Overview .................................... 3 2 General Overview .................................... 3
3 Third Party Call Control Flows ...................... 3 3 Third Party Call Control Flows ...................... 3
3.1 Terminology ......................................... 4 3.1 Terminology ......................................... 4
3.2 Callee's Invocation ................................. 4 3.2 Callee's Invocation ................................. 4
3.3 Caller's Invocation ................................. 9 3.3 Caller's Invocation ................................. 9
3.4 Receiving the Original Stream ....................... 9 3.4 Receiving the Original Stream ....................... 9
3.5 Transcoding Services in Parallel .................... 11 3.5 Transcoding Services in Parallel .................... 11
3.6 Transcoding Services in Serial ...................... 15 3.6 Transcoding Services in Serial ...................... 15
4 Security Considerations ............................. 17 4 Security Considerations ............................. 17
5 Authors' Addresses .................................. 17 5 IANA Considerations ................................. 17
6 Normative References ................................ 17 6 Authors' Addresses .................................. 17
7 Informative References .............................. 18 7 Normative References ................................ 17
8 Informative References .............................. 18
1 Introduction 1 Introduction
The framework for transcoding with SIP [4] describes how two SIP [1] The framework for transcoding with SIP [4] describes how two SIP [1]
UAs (User Agents) can discover imcompatibilities that prevent them UAs (User Agents) can discover imcompatibilities that prevent them
from establishing a session (e.g., lack of support for a common codec from establishing a session (e.g., lack of support for a common codec
or for a common media type). When such incompatibilities are found, or for a common media type). When such incompatibilities are found,
the UAs need to invoke transcoding services to successfully establish the UAs need to invoke transcoding services to successfully establish
the session. 3pcc (third party call control) [2] is one way to the session. 3pcc (third party call control) [2] is one way to
perform such invocation. perform such invocation.
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1. Audio from A to T.example.com:30000 1. Audio from A to T.example.com:30000
2. Text from T to B.example.com:40000 2. Text from T to B.example.com:40000
3. Text from B to T.example.com:30002 3. Text from B to T.example.com:30002
4. Audio from T to A.example.com:20000 4. Audio from T to A.example.com:20000
When either A or B decide to terminate the session, they send a BYE When either A or B decide to terminate the session, they send a BYE
to T indicating that the session is over. indicating that the session is over.
If the first INVITE (1) received by B is empty (no session If the first INVITE (1) received by B is empty (no session
description), the call flow is slightly different. Figure 2 shows the description), the call flow is slightly different. Figure 2 shows the
messages involved. messages involved.
B may have different reasons for invoking T before knowing A's B may have different reasons for invoking T before knowing A's
session description. B may want to hide its capabilities, and session description. B may want to hide its capabilities, and
therefore it wants to return a session description with all the therefore it wants to return a session description with all the
codecs B supports plus all the codecs T supports. Or T may provide codecs B supports plus all the codecs T supports. Or T may provide
recording services (besides transcoding), and B wants T to record the recording services (besides transcoding), and B wants T to record the
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| | | | | | | |
Figure 5: Transcoding services in serial Figure 5: Transcoding services in serial
4 Security Considerations 4 Security Considerations
This document describes how to use third party call control to invoke This document describes how to use third party call control to invoke
transcoding services. It does not introduce new security transcoding services. It does not introduce new security
considerations besides the ones discussed in [2]. considerations besides the ones discussed in [2].
5 Authors' Addresses 5 IANA Considerations
This document has no actions for IANA.
6 Authors' Addresses
Gonzalo Camarillo Gonzalo Camarillo
Ericsson Ericsson
Advanced Signalling Research Lab. Advanced Signalling Research Lab.
FIN-02420 Jorvas FIN-02420 Jorvas
Finland Finland
electronic mail: Gonzalo.Camarillo@ericsson.com electronic mail: Gonzalo.Camarillo@ericsson.com
Eric Burger Eric Burger
Brooktrout Technology, Inc. Brooktrout Technology, Inc.
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Arnoud van Wijk Arnoud van Wijk
Viataal Viataal
Research & Development Research & Development
Afdeling RDS Afdeling RDS
Theerestraat 42 Theerestraat 42
5271 GD Sint-Michielsgestel 5271 GD Sint-Michielsgestel
The Netherlands The Netherlands
electronic mail: a.vwijk@viataal.nl electronic mail: a.vwijk@viataal.nl
6 Normative References 7 Normative References
[1] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. R. Johnston, J. [1] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. R. Johnston, J.
Peterson, R. Sparks, M. Handley, and E. Schooler, "SIP: session Peterson, R. Sparks, M. Handley, and E. Schooler, "SIP: session
initiation protocol," RFC 3261, Internet Engineering Task Force, June initiation protocol," RFC 3261, Internet Engineering Task Force, June
2002. 2002.
[2] J. Rosenberg, J. Peterson, H. Schulzrinne, and G. Camarillo, [2] J. Rosenberg, J. Peterson, H. Schulzrinne, and G. Camarillo,
"Best current practices for third party call control (3pcc) in the "Best current practices for third party call control (3pcc) in the
session initiation protocol (SIP)," RFC 3725, Internet Engineering session initiation protocol (SIP)," RFC 3725, Internet Engineering
Task Force, Apr. 2004. Task Force, Apr. 2004.
[3] G. Camarillo, G. Eriksson, J. Holler, and H. Schulzrinne, [3] G. Camarillo, G. Eriksson, J. Holler, and H. Schulzrinne,
"Grouping of media lines in the session description protocol (SDP)," "Grouping of media lines in the session description protocol (SDP),"
RFC 3388, Internet Engineering Task Force, Dec. 2002. RFC 3388, Internet Engineering Task Force, Dec. 2002.
7 Informative References 8 Informative References
[4] G. Camarillo, "Framework for transcoding with the session [4] G. Camarillo, "Framework for transcoding with the session
initiation protocol," Internet Draft draft-camarillo-sipping-transc- initiation protocol," Internet Draft draft-camarillo-sipping-transc-
framework-00, Internet Engineering Task Force, Aug. 2003. Work in framework-00, Internet Engineering Task Force, Aug. 2003. Work in
progress. progress.
[5] N. Charlton, M. Gasson, G. Gybels, M. Spanner, and A. van Wijk, [5] N. Charlton, M. Gasson, G. Gybels, M. Spanner, and A. van Wijk,
"User requirements for the session initiation protocol (SIP) in "User requirements for the session initiation protocol (SIP) in
support of deaf, hard of hearing and speech-impaired individuals," support of deaf, hard of hearing and speech-impaired individuals,"
RFC 3351, Internet Engineering Task Force, Aug. 2002. RFC 3351, Internet Engineering Task Force, Aug. 2002.
 End of changes. 

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