draft-ietf-avtcore-rfc5285-bis-07.txt   draft-ietf-avtcore-rfc5285-bis-08.txt 
AVTCore R. Even, Ed. AVTCore R. Even, Ed.
Internet-Draft Huawei Technologies Internet-Draft Huawei Technologies
Obsoletes: 5285 (if approved) D. Singer Obsoletes: 5285 (if approved) D. Singer
Intended status: Standards Track Apple, Inc. Intended status: Standards Track Apple, Inc.
Expires: August 29, 2017 H. Desineni Expires: August 31, 2017 H. Desineni
February 25, 2017 February 27, 2017
A General Mechanism for RTP Header Extensions A General Mechanism for RTP Header Extensions
draft-ietf-avtcore-rfc5285-bis-07.txt draft-ietf-avtcore-rfc5285-bis-08.txt
Abstract Abstract
This document provides a general mechanism to use the header This document provides a general mechanism to use the header
extension feature of RTP (the Real-Time Transport Protocol). It extension feature of RTP (the Real-Time Transport Protocol). It
provides the option to use a small number of small extensions in each provides the option to use a small number of small extensions in each
RTP packet, where the universe of possible extensions is large and RTP packet, where the universe of possible extensions is large and
registration is de-centralized. The actual extensions in use in a registration is de-centralized. The actual extensions in use in a
session are signaled in the setup information for that session. This session are signaled in the setup information for that session. This
document obsoletes RFC5285. document obsoletes RFC5285.
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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 August 29, 2017. This Internet-Draft will expire on August 31, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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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of an RTCP packet reporting on an interval where RTP header extension of an RTCP packet reporting on an interval where RTP header extension
packets were sent, does not necessarily mean that the RTP header packets were sent, does not necessarily mean that the RTP header
extension packets themselves were lost. extension packets themselves were lost.
4.1.2. Header Extension Type Considerations 4.1.2. Header Extension Type Considerations
Each extension element in a packet has a local identifier (ID) and a Each extension element in a packet has a local identifier (ID) and a
length. The local identifiers present in the stream MUST have been length. The local identifiers present in the stream MUST have been
negotiated or defined out-of-band. There are no static allocations negotiated or defined out-of-band. There are no static allocations
of local identifiers. Each distinct extension MUST have a unique ID. of local identifiers. Each distinct extension MUST have a unique ID.
The value 0 is reserved for padding and MUST NOT be used as a local The ID value 0 is reserved for padding and MUST NOT be used as a
identifier. local identifier.
an extension element with a value equal 0 MUST NOT have len greater An extension element with an ID value equal 0 MUST NOT have len
than 0. If such an extension element is encountered, its length greater than 0. If such an extension element is encountered, its
field MUST be ignored, processing of the entire extension MUST length field MUST be ignored, processing of the entire extension MUST
terminate at that point, and only the extension elements present terminate at that point, and only the extension elements present
prior to the element with ID 0 and len greater than 0 SHOULD be prior to the element with ID 0 and len greater than 0 SHOULD be
considered. considered.
There are two variants of the extension: one-byte and two-byte There are two variants of the extension: one-byte and two-byte
headers. Since it is expected that (a) the number of extensions in headers. Since it is expected that (a) the number of extensions in
any given RTP session is small and (b) the extensions themselves are any given RTP session is small and (b) the extensions themselves are
small, the one-byte header form is preferred and MUST be supported by small, the one-byte header form is preferred and MUST be supported by
all receivers. A stream MUST contain only one-byte or two-byte all receivers. A stream MUST contain only one-byte or two-byte
headers unless it is known that all recipients support mixing, either headers unless it is known that all recipients support mixing, either
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