draft-ietf-mmusic-fid-05.txt   draft-ietf-mmusic-fid-06.txt 
Internet Engineering Task Force Gonzalo Camarillo Internet Engineering Task Force Gonzalo Camarillo
Internet draft Jan Holler Internet draft Jan Holler
Goran AP Eriksson Goran AP Eriksson
Ericsson Ericsson
Henning Schulzrinne Henning Schulzrinne
Columbia University Columbia University
September 2001 February 2002
Expires March 2002 Expires August 2002
<draft-ietf-mmusic-fid-05.txt> <draft-ietf-mmusic-fid-06.txt>
Grouping of media lines in SDP Grouping of media lines in SDP
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at line 75 skipping to change at line 75
8 Usage of the "group" attribute in SIP.....................11 8 Usage of the "group" attribute in SIP.....................11
8.1 Mid value in responses....................................11 8.1 Mid value in responses....................................11
8.1.1 Example...................................................12 8.1.1 Example...................................................12
8.2 Group value in responses..................................12 8.2 Group value in responses..................................12
8.2.1 Example...................................................13 8.2.1 Example...................................................13
8.3 Capability negotiation....................................14 8.3 Capability negotiation....................................14
8.3.1 Example...................................................14 8.3.1 Example...................................................14
8.4 Backward compatibility....................................14 8.4 Backward compatibility....................................14
8.4.1 Client does not support "group"...........................15 8.4.1 Client does not support "group"...........................15
8.4.2 Server does not support "group"...........................15 8.4.2 Server does not support "group"...........................15
9 IANA considerations.......................................15 9 Security considerations...................................15
10 Acknowledgements..........................................16 10 IANA considerations.......................................16
11 References................................................16 11 Acknowledgements..........................................16
12 Authors³ Addresses........................................16 12 References................................................16
13 Authors³ Addresses........................................16
1 Introduction 1 Introduction
An SDP session description typically contains a number (one or more) An SDP session description typically contains a number (one or more)
of media lines - they are commonly known as "m" lines. When a of media lines - they are commonly known as "m" lines. When a
session description contains more than one "m" line, SDP does not session description contains more than one "m" line, SDP does not
provide any means to express a particular relationship between two provide any means to express a particular relationship between two
or more of them. When an application receives an SDP session or more of them. When an application receives an SDP session
description with more than one "m" line it is up to the application description with more than one "m" line it is up to the application
what to do with them. SDP does not carry any information about what to do with them. SDP does not carry any information about
skipping to change at line 794 skipping to change at line 795
incoming RTP sessions, which is the correct behavior. incoming RTP sessions, which is the correct behavior.
An implementation might also decide to refuse the request (e.g. 488 An implementation might also decide to refuse the request (e.g. 488
Not acceptable here or 606 Not Acceptable) because it contains Not acceptable here or 606 Not Acceptable) because it contains
several "m" lines. In this case, the server does not support the several "m" lines. In this case, the server does not support the
type of session that the caller wanted to establish. In case the type of session that the caller wanted to establish. In case the
client is willing to establish a simpler session anyway, he SHOULD client is willing to establish a simpler session anyway, he SHOULD
re-try the request without "group" attribute and only one "m" line re-try the request without "group" attribute and only one "m" line
per flow. per flow.
9. IANA considerations 9. Security considerations
Using the "group" parameter with FID semantics an entity that
managed to modify the session descriptions exchanged between the
participants to establish a multimedia session could force the
participants to send a copy of the media to any particular
destination.
Integrity mechanism provided by protocols used to exchange session
descriptions and media encryption can be used to prevent this
attack.
Camarillo/Holler/Eriksson/Schulzrinne 15
Grouping of media lines in SDP
10. IANA considerations
This document defines two SDP attributes: "mid" and "group". This document defines two SDP attributes: "mid" and "group".
The "mid" attribute is used to identify media streams within a The "mid" attribute is used to identify media streams within a
session description and its format is defined in Section 3. session description and its format is defined in Section 3.
The "group" attribute is used for grouping together different media The "group" attribute is used for grouping together different media
streams and its format is defined in Section 4. streams and its format is defined in Section 4.
Section 4 also defines two standard semantics related to the "group" Section 4 also defines two standard semantics related to the "group"
attribute: LS (Lip Synchronization) and FID (Flow Identification). attribute: LS (Lip Synchronization) and FID (Flow Identification).
If in the future it was needed to standardize further semantics they If in the future it was needed to standardize further semantics they
would need to be defined in a standards track document. would need to be defined in a standards track document.
Camarillo/Holler/Eriksson/Schulzrinne 15 11. Acknowledgments
Grouping of media lines in SDP
10. Acknowledgments
The authors would like to thank Jonathan Rosenberg, Adam Roach, Orit The authors would like to thank Jonathan Rosenberg, Adam Roach, Orit
Levin and Joerg Ott for their feedback on this document. Levin and Joerg Ott for their feedback on this document.
11. References 12. References
[1] S. Bradner, "Key words for use in RFCs to Indicate Requirement [1] S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, IETF; March 1997. Levels", RFC 2119, IETF; March 1997.
[2] M. Handley/V. Jacobson, "SDP: Session Description Protocol", RFC [2] M. Handley/V. Jacobson, "SDP: Session Description Protocol", RFC
2327, IETF; April 1998. 2327, IETF; April 1998.
[3] H. Schulzrinne/A. Rao/R. Lanphier, "Real Time Streaming Protocol [3] H. Schulzrinne/A. Rao/R. Lanphier, "Real Time Streaming Protocol
(RTSP)", RFC 2326, IETF; April 1998. (RTSP)", RFC 2326, IETF; April 1998.
[4] H. Schulzrinne/S. Casner/R. Frederick/V. Jacobson, "RTP: A [4] H. Schulzrinne/S. Casner/R. Frederick/V. Jacobson, "RTP: A
Transport Protocol for Real-Time Applications", RFC 1889, IETF; Transport Protocol for Real-Time Applications", RFC 1889, IETF;
January 1996. January 1996.
[5] M. Handley/H. Schulzrinne/E. Schooler/J. Rosenberg, "SIP: [5] M. Handley/H. Schulzrinne/E. Schooler/J. Rosenberg, "SIP:
Session Initiation Protocol", RFC 2543, IETF; Mach 1999. Session Initiation Protocol", RFC 2543, IETF; Mach 1999.
[6] H. Schulzrinne/S. Petrack, "RTP Payload for DTMF Digits, [6] H. Schulzrinne/S. Petrack, "RTP Payload for DTMF Digits,
Telephony Tones and Telephony Signals", RFC 2833, IETF; May 2000. Telephony Tones and Telephony Signals", RFC 2833, IETF; May 2000.
12. Authors³ Addresses 13. Authors³ Addresses
Gonzalo Camarillo Gonzalo Camarillo
Ericsson Ericsson
Advanced Signalling Research Lab. Advanced Signalling Research Lab.
FIN-02420 Jorvas FIN-02420 Jorvas
Finland Finland
Phone: +358 9 299 3371 Phone: +358 9 299 3371
Fax: +358 9 299 3052 Fax: +358 9 299 3052
Email: Gonzalo.Camarillo@ericsson.com Email: Gonzalo.Camarillo@ericsson.com
Camarillo/Holler/Eriksson/Schulzrinne 16
Grouping of media lines in SDP
Jan Holler Jan Holler
Ericsson Research Ericsson Research
S-16480 Stockholm S-16480 Stockholm
Sweden Sweden
Phone: +46 8 58532845 Phone: +46 8 58532845
Fax: +46 8 4047020 Fax: +46 8 4047020
Email: Jan.Holler@era.ericsson.se Email: Jan.Holler@era.ericsson.se
Goran AP Eriksson Goran AP Eriksson
Ericsson Research Ericsson Research
S-16480 Stockholm S-16480 Stockholm
Sweden Sweden
Phone: +46 8 58531762 Phone: +46 8 58531762
Fax: +46 8 4047020 Fax: +46 8 4047020
Email: Goran.AP.Eriksson@era.ericsson.se Email: Goran.AP.Eriksson@era.ericsson.se
Camarillo/Holler/Eriksson/Schulzrinne 16
Grouping of media lines in SDP
Henning Schulzrinne Henning Schulzrinne
Dept. of Computer Science Dept. of Computer Science
Columbia University Columbia University
1214 Amsterdam Avenue 1214 Amsterdam Avenue
New York, NY 10027 New York, NY 10027
USA USA
Email: schulzrinne@cs.columbia.edu Email: schulzrinne@cs.columbia.edu
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Grouping of media lines in SDP
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