draft-ietf-mmusic-offer-answer-examples-01.txt   draft-ietf-mmusic-offer-answer-examples-02.txt 
MMUSIC Working Group A. Johnston MMUSIC Working Group A. Johnston
Internet-Draft MCI Internet-Draft MCI
Expires: December 27, 2003 R. Sparks Expires: August 15, 2004 R. Sparks
dynamicsoft dynamicsoft
June 28, 2003 February 15, 2004
Session Description Protocol Offer Answer Examples Session Description Protocol Offer Answer Examples
draft-ietf-mmusic-offer-answer-examples-01 draft-ietf-mmusic-offer-answer-examples-02
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract Abstract
This document gives examples of Session Description Protocol (SDP) This document gives examples of Session Description Protocol (SDP)
offer answer exchanges. Examples include codec negotiation and offer answer exchanges. Examples include codec negotiation and
selection, hold and resume, and addition and deletion of media selection, hold and resume, and addition and deletion of media
streams. The examples show multiple media types, bidirectional, streams. The examples show multiple media types, bidirectional,
unidirectional, inactive streams and dynamic payload types. Common unidirectional, inactive streams and dynamic payload types. Common
Third Party Call Control (3pcc) examples are also given. Third Party Call Control (3pcc) examples are also given.
Table of Contents Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Codec Negotiation and Selection . . . . . . . . . . . . . . 3 2. Codec Negotiation and Selection . . . . . . . . . . . . . . . 3
2.1 Audio and Video 1 . . . . . . . . . . . . . . . . . . . . . 3 2.1 Audio and Video 1 . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Audio and Video 2 . . . . . . . . . . . . . . . . . . . . . 4 2.2 Audio and Video 2 . . . . . . . . . . . . . . . . . . . . . . 4
2.3 Audio and Video 3 . . . . . . . . . . . . . . . . . . . . . 5 2.3 Audio and Video 3 . . . . . . . . . . . . . . . . . . . . . . 6
2.4 Two Audio Steams . . . . . . . . . . . . . . . . . . . . . . 6 2.4 Two Audio Steams . . . . . . . . . . . . . . . . . . . . . . . 6
2.5 Audio and Video 4 . . . . . . . . . . . . . . . . . . . . . 7 2.5 Audio and Video 4 . . . . . . . . . . . . . . . . . . . . . . 7
2.6 Audio Only 1 . . . . . . . . . . . . . . . . . . . . . . . . 8 2.6 Audio Only 1 . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.7 Audio and Video 5 . . . . . . . . . . . . . . . . . . . . . 9 2.7 Audio and Video 5 . . . . . . . . . . . . . . . . . . . . . . 9
2.8 Audio and Video 6 . . . . . . . . . . . . . . . . . . . . . 10 2.8 Audio and Video 6 . . . . . . . . . . . . . . . . . . . . . . 11
2.9 Asymmetric Codec Types . . . . . . . . . . . . . . . . . . . 11 3. Hold and Resume Scenarios . . . . . . . . . . . . . . . . . . 11
2.10 Asymmetric Attribute Values . . . . . . . . . . . . . . . . 12 3.1 Hold and Unhold 1 . . . . . . . . . . . . . . . . . . . . . . 11
3. Hold and Resume Scenarios . . . . . . . . . . . . . . . . . 13 3.2 Hold with Two Streams . . . . . . . . . . . . . . . . . . . . 13
3.1 Hold and Unhold 1 . . . . . . . . . . . . . . . . . . . . . 13 4. Addition and Deletion of Media Streams . . . . . . . . . . . . 14
3.2 Hold with Two Streams . . . . . . . . . . . . . . . . . . . 14 4.1 Second Audio Stream Added . . . . . . . . . . . . . . . . . . 14
4. Addition and Deletion of Media Streams . . . . . . . . . . . 16 4.2 Audio then Video Added . . . . . . . . . . . . . . . . . . . . 15
4.1 Second Audio Stream Added . . . . . . . . . . . . . . . . . 16 4.3 Audio and Video, then Video Deleted . . . . . . . . . . . . . 16
4.2 Audio then Video Added . . . . . . . . . . . . . . . . . . . 17 5. Third Party Call Control (3pcc) . . . . . . . . . . . . . . . 18
4.3 Audio and Video, then Video Deleted . . . . . . . . . . . . 18 5.1 No Media, then Audio Added . . . . . . . . . . . . . . . . . . 18
5. Third Party Call Control (3pcc) . . . . . . . . . . . . . . 19 5.2 Hold and Unhold 2 . . . . . . . . . . . . . . . . . . . . . . 19
5.1 No Media, then Audio Added . . . . . . . . . . . . . . . . . 20 5.3 Hold and Unhold 3 . . . . . . . . . . . . . . . . . . . . . . 20
5.2 Hold and Unhold 2 . . . . . . . . . . . . . . . . . . . . . 20 6. Security Considerations . . . . . . . . . . . . . . . . . . . 21
5.3 Hold and Unhold 3 . . . . . . . . . . . . . . . . . . . . . 22 7. Changes since -00 . . . . . . . . . . . . . . . . . . . . . . 21
6. Security Considerations . . . . . . . . . . . . . . . . . . 23 8. Changes since -01 . . . . . . . . . . . . . . . . . . . . . . 21
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23 Informative References . . . . . . . . . . . . . . . . . . . . 21
8. Changes since -00 . . . . . . . . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 22
Informative References . . . . . . . . . . . . . . . . . . . 23 Intellectual Property and Copyright Statements . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 24
Intellectual Property and Copyright Statements . . . . . . . 25
1. Overview 1. Overview
This document describes offer answer examples of Session Description This document describes offer answer examples of Session Description
Protocol (SDP) based on RFC 3264 [1]. The SDP in these examples are Protocol (SDP) based on RFC 3264 [1]. The SDP in these examples are
defined by RFC 2327 [2]. The offers and answers are assumed to be defined by RFC 2327 [2]. The offers and answers are assumed to be
transported using a protocol such as Session Initiation Protocol transported using a protocol such as Session Initiation Protocol
(SIP) [3]. (SIP) [3].
Examples include codec negotiation and selection, hold and resume, Examples include codec negotiation and selection, hold and resume,
skipping to change at page 11, line 22 skipping to change at page 11, line 41
o=bob 2808844564 2808844564 IN IP4 host.biloxi.example.com o=bob 2808844564 2808844564 IN IP4 host.biloxi.example.com
s= s=
c=IN IP4 host.biloxi.example.com c=IN IP4 host.biloxi.example.com
t=0 0 t=0 0
m=audio 49174 RTP/AVP 0 m=audio 49174 RTP/AVP 0
a=rtpmap:0 PCMU/8000 a=rtpmap:0 PCMU/8000
m=video 49172 RTP/AVP 32 m=video 49172 RTP/AVP 32
c=IN IP4 otherhost.biloxi.example.com c=IN IP4 otherhost.biloxi.example.com
a=rtpmap:32 MPV/90000 a=rtpmap:32 MPV/90000
2.9 Asymmetric Codec Types
This scenario shows a video and audio session where it is desired to
agree on different audio and video codecs in each direction. An
example for the need to establish an asymmetric session is when
running over asymmetric bandwidth links such as ADSL.
In this simplest case the logical association between the send-only
and the receive-only streams is expressed by specifying the same port
number in both m-lines. Because no explicit RTCP attribute [7] is
included, usage of the port number in sendonly direction, which
equals to the port number in recvonly direction, unambiguously hints
that the two m-lines share the same RTCP bidirectional stream and
belong to the same RTP session.
Note: When the RTCP attribute needs to be used, alternative means for
association between the m-lines will be used [8].
[Offer]
v=0
o=alice 2890844526 2890844526 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 95
a=rtpmap:95 iLBC
a=sendonly
m=audio 49170 RTP/AVP 0 8
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=recvonly
m=video 51372 RTP/AVP 31 32
a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000
a=sendonly
m=video 51372 RTP/AVP 34
a=rtpmap:34 H263/90000
a=recvonly
[Answer]
v=0
o=bob 2808844564 2808844564 IN IP4 host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49178 RTP/AVP 95
a=rtpmap:iLBC
a=recvonly
m=audio 49178 RTP/AVP 0
a=rtpmap:0 PCMU/8000
a=sendonly
m=video 51374 RTP/AVP 31
a=rtpmap:31 H261/90000
a=recvonly
m=video 51374 RTP/AVP 34
a=rtpmap:34 H263/90000
a=sendonly
2.10 Asymmetric Attribute Values
This scenario shows an audio session where it is desired to agree on
audio codecs with different parameters (attributes) in each
direction. An example for the need to establish an asymmetric session
is when running over asymmetric bandwidth links such as ADSL.
In this simplest case the logical association between the send-only
and the receive-only streams is expressed by specifying the same port
number in both m-lines. Because no explicit RTCP attribute [7] is
included, usage of the port number in sendonly direction, which
equals to the port number in recvonly direction, unambiguously hints
that the two m-lines share the same RTCP bidirectional stream and
belong to the same RTP session.
Note: When the RTCP attribute needs to be used, alternative means for
association between the m-lines will be used [8].
[Offer]
v=0
o=alice 2890844526 2890844526 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 97
a=rtpmap:97 MPA
a=fmtp: 97 layer=3 bitrate=10
a=sendonly
m=audio 49170 RTP/AVP 97
a=rtpmap:97 MPA
a=fmtp:97 layer=3 bitrate=60
a=recvonly
[Answer]
v=0
o=bob 2808844564 2808844564 IN IP4 host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49178 RTP/AVP 97
a=rtpmap:MPA
a=fmtp:97 layer=3 bitrate=10
a=recvonly
m=audio 49178 RTP/AVP 97
a=rtpmap:MPA
a=fmtp:97 layer=3 bitrate=60
a=sendonly
3. Hold and Resume Scenarios 3. Hold and Resume Scenarios
3.1 Hold and Unhold 1 3.1 Hold and Unhold 1
Alice calls Bob, but Bob answers placing Alice on hold. Bob then Alice calls Bob, but Bob answers placing Alice on hold. Bob then
takes Alice off hold in the second offer. Alice changes port number takes Alice off hold in the second offer. Alice changes port number
in the second exchange. The media session between Alice and Bob is in the second exchange. The media session between Alice and Bob is
now active after Alice's second answer. Note that a=sendrecv could now active after Alice's second answer. Note that a=sendrecv could
be present in both second offer and answer exchange. This is a be present in both second offer and answer exchange. This is a
common flow in 3pcc [5] scenarios. common flow in 3pcc [5] scenarios.
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6. Security Considerations 6. Security Considerations
SDP offer and answer messages can contain private information about SDP offer and answer messages can contain private information about
addresses and sessions to be established between parties. If this addresses and sessions to be established between parties. If this
information needs to be kept private, some security mechanism in the information needs to be kept private, some security mechanism in the
protocol used to carry the offers and answers must be used. For SIP, protocol used to carry the offers and answers must be used. For SIP,
this means using TLS transport and/or S/MIME encryption of the SDP this means using TLS transport and/or S/MIME encryption of the SDP
message body. message body.
7. Acknowledgements 7. Changes since -00
Thanks to Orit Levin for the asymmetrical codec and attribute - Added asymmetrical codec and attribute examples
examples.
8. Changes since -00 8. Changes since -01
- Added asymmetrical codec and attribute examples - Removed asymmetrical codec and attribute examples
- Updated references
Informative References Informative References
[1] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with [1] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
Session Description Protocol (SDP)", RFC 3264, June 2002. Session Description Protocol (SDP)", RFC 3264, June 2002.
[2] Handley, M. and V. Jacobson, "SDP: Session Description [2] Handley, M. and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998. Protocol", RFC 2327, April 1998.
[3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., [3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002. Session Initiation Protocol", RFC 3261, June 2002.
[4] Schulzrinne, H. and S. Petrack, "RTP Payload for DTMF Digits, [4] Schulzrinne, H. and S. Petrack, "RTP Payload for DTMF Digits,
Telephony Tones and Telephony Signals", RFC 2833, May 2000. Telephony Tones and Telephony Signals", RFC 2833, May 2000.
[5] Rosenberg, J., Peterson, J., Schulzrinne, H. and G. Camarillo, [5] Rosenberg, J., Peterson, J., Schulzrinne, H. and G. Camarillo,
"Best Current Practices for Third Party Call Control in the "Best Current Practices for Third Party Call Control in the
Session Initiation Protocol", draft-ietf-sipping-3pcc-03 (work Session Initiation Protocol", draft-ietf-sipping-3pcc-06 (work
in progress), March 2003. in progress), January 2004.
[6] Duric, A. and S. Andersen, "RTP Payload Format for iLBC Speech", [6] Duric, A. and S. Andersen, "RTP Payload Format for iLBC Speech",
draft-ietf-avt-rtp-ilbc-01 (work in progress), March 2003. draft-ietf-avt-rtp-ilbc-04 (work in progress), December 2003.
[7] Huitema, C., "RTCP attribute in SDP",
draft-ietf-mmusic-sdp4nat-05 (work in progress), June 2003.
[8] Camarillo, G., Eriksson, G., Holler, J. and H. Schulzrinne, [7] Camarillo, G., Eriksson, G., Holler, J. and H. Schulzrinne,
"Grouping of Media Lines in the Session Description Protocol "Grouping of Media Lines in the Session Description Protocol
(SDP)", RFC 3388, December 2002. (SDP)", RFC 3388, December 2002.
Authors' Addresses Authors' Addresses
Alan Johnston Alan Johnston
MCI MCI
100 South 4th Street 100 South 4th Street
St. Louis, MO 63102 St. Louis, MO 63102
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