Differentiated Services (Diffserv) and Real-Time Communication
RFC 7657
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RFC - Informational
(November 2015; No errata)
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Last updated |
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2015-11-18
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IETF
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Ben Campbell
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(last changed 2014-08-31)
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RFC 7657 (Informational)
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Internet Engineering Task Force (IETF) D. Black, Ed.
Request for Comments: 7657 EMC
Category: Informational P. Jones
ISSN: 2070-1721 Cisco
November 2015
Differentiated Services (Diffserv) and Real-Time Communication
Abstract
This memo describes the interaction between Differentiated Services
(Diffserv) network quality-of-service (QoS) functionality and real-
time network communication, including communication based on the
Real-time Transport Protocol (RTP). Diffserv is based on network
nodes applying different forwarding treatments to packets whose IP
headers are marked with different Diffserv Codepoints (DSCPs).
WebRTC applications, as well as some conferencing applications, have
begun using the Session Description Protocol (SDP) bundle negotiation
mechanism to send multiple traffic streams with different QoS
requirements using the same network 5-tuple. The results of using
multiple DSCPs to obtain different QoS treatments within a single
network 5-tuple have transport protocol interactions, particularly
with congestion control functionality (e.g., reordering). In
addition, DSCP markings may be changed or removed between the traffic
source and destination. This memo covers the implications of these
Diffserv aspects for real-time network communication, including
WebRTC.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
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). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7657.
Black & Jones Informational [Page 1]
RFC 7657 Diffserv and RT Communication November 2015
Copyright Notice
Copyright (c) 2015 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Real-Time Communications . . . . . . . . . . . . . . . . . . 3
2.1. RTP Background . . . . . . . . . . . . . . . . . . . . . 4
2.2. RTP Multiplexing . . . . . . . . . . . . . . . . . . . . 6
3. Differentiated Services (Diffserv) . . . . . . . . . . . . . 7
3.1. Diffserv Per-Hop Behaviors (PHBs) . . . . . . . . . . . . 10
3.2. Traffic Classifiers and DSCP Remarking . . . . . . . . . 10
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Diffserv Interactions . . . . . . . . . . . . . . . . . . . . 13
5.1. Diffserv, Reordering, and Transport Protocols . . . . . . 13
5.2. Diffserv, Reordering, and Real-Time Communication . . . . 15
5.3. Drop Precedence and Transport Protocols . . . . . . . . . 16
5.4. Diffserv and RTCP . . . . . . . . . . . . . . . . . . . . 17
6. Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . 18
7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.1. Normative References . . . . . . . . . . . . . . . . . . 20
8.2. Informative References . . . . . . . . . . . . . . . . . 22
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
Black & Jones Informational [Page 2]
RFC 7657 Diffserv and RT Communication November 2015
1. Introduction
This memo describes the interactions between Differentiated Services
(Diffserv) network quality-of-service (QoS) functionality [RFC2475]
and real-time network communication, including communication based on
the Real-time Transport Protocol (RTP) [RFC3550]. Diffserv is based
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