RTP Stream Identifier Source Description (SDES)
RFC 8852
| Document | Type | RFC - Proposed Standard (January 2021; No errata) | |
|---|---|---|---|
| Authors | Adam Roach , Suhas Nandakumar , Peter Thatcher | ||
| Last updated | 2021-01-19 | ||
| Replaces | draft-roach-avtext-rid | ||
| Stream | IETF | ||
| Formats | plain text html xml pdf htmlized bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Jonathan Lennox | ||
| Shepherd write-up | Show (last changed 2016-07-07) | ||
| IESG | IESG state | RFC 8852 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Ben Campbell | ||
| Send notices to | "Jonathan Lennox" <jonathan@vidyo.com> | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA action state | RFC-Ed-Ack | ||
Internet Engineering Task Force (IETF) A.B. Roach
Request for Comments: 8852 Mozilla
Category: Standards Track S. Nandakumar
ISSN: 2070-1721 Cisco Systems
P. Thatcher
Google
January 2021
RTP Stream Identifier Source Description (SDES)
Abstract
This document defines and registers two new Real-time Transport
Control Protocol (RTCP) Stream Identifier Source Description (SDES)
items. One, named RtpStreamId, is used for unique identification of
RTP streams. The other, RepairedRtpStreamId, can be used to identify
which stream is to be repaired using a redundancy RTP stream.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8852.
Copyright Notice
Copyright (c) 2021 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
(https://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.
Table of Contents
1. Introduction
2. Terminology
3. Usage of RtpStreamId and RepairedRtpStreamId in RTP and RTCP
3.1. RTCP "RtpStreamId" SDES Extension
3.2. RTCP "RepairedRtpStreamId" SDES Extension
3.3. RTP "RtpStreamId" and "RepairedRtpStreamId" Header
Extensions
4. IANA Considerations
4.1. New RtpStreamId SDES Item
4.2. New RepairRtpStreamId SDES Item
4.3. New RtpStreamId Header Extension URI
4.4. New RepairRtpStreamId Header Extension URI
5. Security Considerations
6. References
6.1. Normative References
6.2. Informative References
Acknowledgements
Authors' Addresses
1. Introduction
RTP sessions frequently consist of multiple streams, each of which is
identified at any given time by its synchronization source (SSRC);
however, the SSRC associated with a stream is not guaranteed to be
stable over its lifetime. Within a session, these streams can be
tagged with a number of identifiers, including CNAMEs and MediaStream
Identification (MSID) [RFC8830]. Unfortunately, none of these have
the proper ordinality to refer to an individual stream; all such
identifiers can appear in more than one stream at a time. While
approaches that use unique payload types (PTs) per stream have been
used in some applications, this is a semantic overloading of that
field, and one for which its size is inadequate: in moderately
complex systems that use PT to uniquely identify every potential
combination of codec configuration and unique stream, it is possible
to simply run out of values.
To address this situation, we define a new RTCP Stream Identifier
Source Description (SDES) identifier, RtpStreamId, that uniquely
identifies a single RTP stream. A key motivator for defining this
identifier is the ability to differentiate among different encodings
of a single source stream that are sent simultaneously (i.e.,
simulcast). This need for unique identification extends to dependent
streams (e.g., where layers used by a layered codec are transmitted
on separate streams).
At the same time, when redundancy RTP streams are in use, we also
need an identifier that connects such streams to the RTP stream for
which they are providing redundancy. For this purpose, we define an
additional SDES identifier, RepairedRtpStreamId. This identifier can
appear only in packets associated with a redundancy RTP stream. They
carry the same value as the RtpStreamId of the RTP stream that the
redundant RTP stream is correcting.
2. Terminology
In this document, the terms "source stream", "RTP stream", "source
RTP stream", "dependent stream", "received RTP stream", and
"redundancy RTP stream" are used as defined in [RFC7656].
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