draft-ietf-mmusic-sdp-g723-g729-03.txt   draft-ietf-mmusic-sdp-g723-g729-04.txt 
MMUSIC Muthu A M. Perumal MMUSIC Muthu A M. Perumal
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Updates: 4856 (if approved) Parthasarathi. Ravindran Updates: 4856 (if approved) Parthasarathi. Ravindran
Intended status: Standards Track Nokia Siemens Networks Intended status: Standards Track Nokia Siemens Networks
Expires: December 19, 2013 June 17, 2013 Expires: January 16, 2014 July 15, 2013
Offer/Answer Considerations for G723 Annex A and G729 Annex B Offer/Answer Considerations for G723 Annex A and G729 Annex B
draft-ietf-mmusic-sdp-g723-g729-03 draft-ietf-mmusic-sdp-g723-g729-04
Abstract Abstract
RFC4856 describes the annexa parameter for G723 and the annexb RFC4856 describes the annexa parameter for G723 and the annexb
parameter for G729, G729D and G729E. However, the specification does parameter for G729, G729D and G729E. However, the specification does
not describe the offerer and answerer behavior when the value of the not describe the offerer and answerer behavior when the value of the
annexa or annexb parameter does not match in the Session Description annexa or annexb parameter does not match in the Session Description
protocol(SDP) offer and answer. This document provides the offer/ protocol(SDP) offer and answer. This document provides the offer/
answer considerations for these parameters and updates RFC4856. answer considerations for these parameters and updates RFC4856.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 19, 2013. This Internet-Draft will expire on January 16, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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3. Offer/Answer Considerations 3. Offer/Answer Considerations
[RFC3551] states that [RFC3551] states that
Receivers MUST accept comfort noise frames if restriction of their Receivers MUST accept comfort noise frames if restriction of their
use has not been signaled. The MIME registration for G729 in RFC use has not been signaled. The MIME registration for G729 in RFC
3555 specifies a parameter that MAY be used with MIME or SDP to 3555 specifies a parameter that MAY be used with MIME or SDP to
restrict the use of comfort noise frames. restrict the use of comfort noise frames.
Based on the above, it is best not to use comfort noise frames if the Hence, if the SDP offer or answer indicates that comfort noise is not
SDP offer or answer indicates that comfort noise is not supported. supported, comfort noise frames MUST NOT be used.
3.1. Offer/Answer Considerations for G723 Annex A 3.1. Offer/Answer Considerations for G723 Annex A
The general objective of the below offer/answer considerations is to
make sure that if the offerer or answerer indicates it does not
support Annex A, Annex A is not used.
When the offer or answer has G723 and the annexa parameter is absent, When the offer or answer has G723 and the annexa parameter is absent,
the offerer or answerer knows that it has implied the default the offerer or answerer knows that it has implied the default
"annexa=yes". This is because the annexa attribute is part of the "annexa=yes". This is because the annexa attribute is part of the
original registration of audio/G723 [RFC4856]. All implementations original registration of audio/G723 [RFC4856]. All implementations
that support G723 understand the annexa attribute. Hence, this case that support G723 understand the annexa attribute. Hence, this case
MUST be considered as if the offer or answer has G723 with MUST be considered as if the offer or answer has G723 with
annexa=yes. annexa=yes.
When the offer has G723 with annexa=yes and the answer has G723 with When the offer has G723 with annexa=yes and the answer has G723 with
annexa=no, the offerer and answerer MUST proceed as if G723 is annexa=no, the offerer and answerer MUST proceed as if G723 is
negotiated with annexa=no. negotiated with annexa=no.
When the offer has G723 with annexa=no then the answer MUST NOT have When the offer has G723 with annexa=no, after the offer/answer
annexa=yes for G723. Thus the annexa parameter can be turned off by completion the offerer and answerer MUST proceed as if G723 is
the answerer, but cannot be turned on. negotiated with annexa=no.
When the offer has G723 with annexa=no, the reason for not mandating When the offer has G723 with annexa=no, the reason for not
that the answer MUST have annexa=no for G723 is that there are there mandating that the answer MUST have annexa=no for G723 is that
implementations that omit the annexa parameter in answer and expect there are implementations that omit the annexa parameter in
the least common denominator to be used. answer. In such case the offerer and answerer proceed as if G723
is negotiated with annexa=no.
When the offer has G723 with no annexa parameter and the answer has When the offer has G723 with no annexa parameter and the answer has
G723 with annexa=yes, the offerer and answerer MUST proceed as if G723 with annexa=yes, the offerer and answerer MUST proceed as if
G723 is negotiated with annexa=yes. G723 is negotiated with annexa=yes.
3.2. Offer/Answer Considerations for G729 Annex B, G729D Annex B and 3.2. Offer/Answer Considerations for G729 Annex B, G729D Annex B and
G729E Annex B G729E Annex B
In this section G729 represents any of G729 or G729D or G729E. In this section G729 represents any of G729 or G729D or G729E.
The general objective of the below offer/answer considerations is to
make sure that if the offerer or answerer indicates it does not
support Annex B, Annex B is not used.
When the offer or answer has G729 and the annexb parameter is absent, When the offer or answer has G729 and the annexb parameter is absent,
the offerer or answerer knows that it has implied the default the offerer or answerer knows that it has implied the default
"annexb=yes". This is because the annexb attribute is part of the "annexb=yes". This is because the annexb attribute is part of the
original registration of audio/G729 [RFC4856]. All implementations original registration of audio/G729 [RFC4856]. All implementations
that support G729 understand the annexb attribute. Hence, this case that support G729 understand the annexb attribute. Hence, this case
MUST be considered as if the offer or answer has G729 with MUST be considered as if the offer or answer has G729 with
annexb=yes. annexb=yes.
When the offer or answer has G729 and the annexb parameter is absent,
it MUST be considered as if the offer or answer has G729 with
annexb=yes.
When the offer has G729 with annexb=yes and the answer has G729 with When the offer has G729 with annexb=yes and the answer has G729 with
annexb=no, the offerer and answerer MUST proceed as if G729 is annexb=no, the offerer and answerer MUST proceed as if G729 is
negotiated with annexb=no. negotiated with annexb=no.
When the offer has G729 with annexb=no then the answer MUST NOT have When the offer has G729 with annexb=no, after the offer/answer
annexb=yes for G729. Thus the annexb parameter can be turned off by completion the offerer and answerer MUST proceed as if G729 is
the answerer, but cannot be turned on. negotiated with annexb=no.
When the offer has G729 with annexa=no, the reason for not mandating When the offer has G729 with annexb=no, the reason for not
that the answer MUST have annexa=no for G729 is that there are there mandating that the answer MUST have annexb=no for G729 is that
implementations that omit the annexa parameter in answer and expect there are implementations that omit the annexb parameter in
the least common denominator to be used. answer. In such case the offerer and answerer proceed as if G729
is negotiated with annexb=no.
When the offer has G729 with no annexb parameter and the answer has When the offer has G729 with no annexb parameter and the answer has
G729 with annexb=yes, the offerer and answerer MUST proceed as if G729 with annexb=yes, the offerer and answerer MUST proceed as if
G729 is negotiated with annexb=yes. G729 is negotiated with annexb=yes.
4. Examples 4. Examples
4.1. Offer with G729 annexb=yes and answer with G729 annexb=no 4.1. Offer with G729 annexb=yes and answer with G729 annexb=no
[Offer with G729 annexb=yes] [Offer with G729 annexb=yes]
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There is no extra security consideration apart from what is described There is no extra security consideration apart from what is described
in [RFC4856]. in [RFC4856].
6. IANA Considerations 6. IANA Considerations
There is no IANA consideration for this draft. There is no IANA consideration for this draft.
7. Acknowledgement 7. Acknowledgement
Thanks to Flemming Andreasen (Cisco), Miguel A. Garcia (Ericsson), Thanks to Flemming Andreasen (Cisco), Miguel A. Garcia (Ericsson),
Ali C. Begen (Cisco), Paul Kyzivat(Huawei), Roni Even (Huawei), Kevin Ali C. Begen (Cisco), Paul Kyzivat (Huawei), Roni Even (Huawei),
Riley (Sonus), Ashish Sharma (Sonus), Kevin P. Fleming (Digium), Dale Kevin Riley (Sonus), Ashish Sharma (Sonus), Kevin P. Fleming
worley, Cullen Jennings (Cisco), Ari Keranen (Ericsson) and Harprit (Digium), Dale Worley (Avaya), Cullen Jennings (Cisco), Ari Keranen
S. Chhatwal (InnoMedia) for their valuable inputs and comments. (Ericsson), Harprit S. Chhatwal (InnoMedia) and Aurelien Sollaud
Martin Dolly (ATT) and Hadriel Kaplan (Acme Packet) provided useful (Orange) for their valuable inputs and comments. Martin Dolly (ATT)
suggestions at the mic at IETF-83. and Hadriel Kaplan (Acme Packet) provided useful suggestions at the
mic at IETF-83.
8. Normative References 8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, with Session Description Protocol (SDP)", RFC 3264,
June 2002. June 2002.
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