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draft-holmberg-mmusic-oa-pt.txt
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draft-holmberg-mmusic-oa-pt.txt
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Network Working Group C. Holmberg
Internet-Draft Ericsson
Updates: 3264 (if approved) February 25, 2016
Intended status: Standards Track
Expires: August 28, 2016
SDP Offer/Answer: Payload type number usage clarification
draft-ietf-mmusic-dtls-sdp-00.txt
Abstract
This document updates RFC 3264 by clarifying the scope of a mapping
from a particular dynamic payload type number to a codec (or codec
configuration) is for a given RTP media flow direction within a
session.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 28, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Holmberg Expires August 28, 2016 [Page 1]
Internet-DraftSDP Offer/Answer: Payload type number usage cFebruary 2016
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Update to RFC 3264 . . . . . . . . . . . . . . . . . . . . . 2
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
6. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 4
7. Normative References . . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
This document updates RFC 3264 [RFC3264] by clarifying the scope of a
mapping from a particular dynamic payload type number to a codec (or
codec configuration) is for a given RTP media flow direction within a
session.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Update to RFC 3264
This section updates the first paragraph of section 8.3.2 of RFC
3264.
Holmberg Expires August 28, 2016 [Page 2]
Internet-DraftSDP Offer/Answer: Payload type number usage cFebruary 2016
Update to section 8.3.2
-----------------------
OLD TEXT:
The list of media formats used in the session MAY be changed. To do
this, the offerer creates a new media description, with the list of
media formats in the "m=" line different from the corresponding media
stream in the previous SDP. This list MAY include new formats, and
MAY remove formats present from the previous SDP. However, in the
case of RTP, the mapping from a particular dynamic payload type
number to a particular codec within that media stream MUST NOT change
for the duration of a session. For example, if A generates an offer
with G.711 assigned to dynamic payload type number 46, payload type
number 46 MUST refer to G.711 from that point forward in any offers
or answers for that media stream within the session. However, it is
acceptable for multiple payload type numbers to be mapped to the same
codec, so that an updated offer could also use payload type number 72
for G.711.
NEW TEXT:
The list of media formats used in the session MAY be changed. To do
this, the offerer creates a new media description, with the list of
media formats in the "m=" line different from the corresponding media
stream in the previous SDP. This list MAY include new formats, and
MAY remove formats present from the previous SDP. The scope of a mapping
from a particular dynamic payload type number to a codec (or codec
configuration) is for a given RTP media flow direction within a session.
The same dynamic payload type number can be mapped to another codec in
another RTP media flow direction within the same session. The mapping
MUST NOT change to a different coded (or coded configuration) for the
duration of a session. Eventhough not recommended, for a given direction,
multiple dynamic payload type numbers can be mapped to the same codec
(or codec configuration). Note that a mapping has been created once an
endpoint has sent and offer or answer, describing the mapping for a
given direction. Even if the offer or answer is rejected or discarded,
or if RTP media associated with the mapping is never sent, the mapping
MUST NOT change for the given direction within the session.
Within an offer or answer, the mapping is for the RTP media flow direction
towards the offerer/answerer, unless the media flow is indicated as 'sendonly'
in which case the mapping is for the media flow direction from the
offerer/answerer.
Holmberg Expires August 28, 2016 [Page 3]
Internet-DraftSDP Offer/Answer: Payload type number usage cFebruary 2016
4. Security Considerations
The security considerations associated with the SDP offer/answer
mechanism are described in RFC 3264. As this document only clarifies
the existing procedures, it does not impact the security
considerations.
5. Acknowledgements
TBD
6. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-holmberg-mmusic-od-pt-xx
o Add text
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002,
<http://www.rfc-editor.org/info/rfc3264>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>.
Author's Address
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
Holmberg Expires August 28, 2016 [Page 4]