draft-ietf-avtcore-6222bis-03.txt   draft-ietf-avtcore-6222bis-04.txt 
Network Working Group A. Begen Network Working Group A. Begen
Internet-Draft Cisco Internet-Draft Cisco
Obsoletes: 6222 (if approved) C. Perkins Obsoletes: 6222 (if approved) C. Perkins
Intended status: Standards Track University of Glasgow Intended status: Standards Track University of Glasgow
Expires: October 25, 2013 D. Wing Expires: December 21, 2013 D. Wing
Cisco Cisco
E. Rescorla E. Rescorla
RTFM, Inc. RTFM, Inc.
April 23, 2013 June 19, 2013
Guidelines for Choosing RTP Control Protocol (RTCP) Guidelines for Choosing RTP Control Protocol (RTCP)
Canonical Names (CNAMEs) Canonical Names (CNAMEs)
draft-ietf-avtcore-6222bis-03 draft-ietf-avtcore-6222bis-04
Abstract Abstract
The RTP Control Protocol (RTCP) Canonical Name (CNAME) is a The RTP Control Protocol (RTCP) Canonical Name (CNAME) is a
persistent transport-level identifier for an RTP endpoint. While the persistent transport-level identifier for an RTP endpoint. While the
Synchronization Source (SSRC) identifier of an RTP endpoint may Synchronization Source (SSRC) identifier of an RTP endpoint may
change if a collision is detected or when the RTP application is change if a collision is detected or when the RTP application is
restarted, its RTCP CNAME is meant to stay unchanged, so that RTP restarted, its RTCP CNAME is meant to stay unchanged, so that RTP
endpoints can be uniquely identified and associated with their RTP endpoints can be uniquely identified and associated with their RTP
media streams. media streams.
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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 October 25, 2013. This Internet-Draft will expire on December 21, 2013.
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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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 3
3. Deficiencies with Earlier Guidelines for Choosing an RTCP 3. Deficiencies with Earlier Guidelines for Choosing an RTCP
CNAME . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 CNAME . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Choosing an RTCP CNAME . . . . . . . . . . . . . . . . . . . 4 4. Choosing an RTCP CNAME . . . . . . . . . . . . . . . . . . . 4
4.1. Persistent RTCP CNAMEs versus Per-Session RTCP CNAMEs . . 4 4.1. Persistent RTCP CNAMEs versus Per-Session RTCP CNAMEs . . 4
4.2. Requirements . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Requirements . . . . . . . . . . . . . . . . . . . . . . 5
5. Procedure to Generate a Unique Identifier . . . . . . . . . . 6 5. Procedure to Generate a Unique Identifier . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6.1. Considerations on Uniqueness of RTCP CNAMEs . . . . . . . 7 6.1. Considerations on Uniqueness of RTCP CNAMEs . . . . . . . 7
6.2. Session Correlation Based on RTCP CNAMEs . . . . . . . . 7 6.2. Session Correlation Based on RTCP CNAMEs . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
In Section 6.5.1 of the RTP specification, [RFC3550], there are a In Section 6.5.1 of the RTP specification, [RFC3550], there are a
number of recommendations for choosing a unique RTCP CNAME for an RTP number of recommendations for choosing a unique RTCP CNAME for an RTP
endpoint. However, in practice, some of these methods are not endpoint. However, in practice, some of these methods are not
guaranteed to produce a unique RTCP CNAME. [RFC6222] updated the guaranteed to produce a unique RTCP CNAME. [RFC6222] updated the
guidelines for choosing RTCP CNAMEs, superseding those presented in guidelines for choosing RTCP CNAMEs, superseding those presented in
Section 6.5.1 of [RFC3550]. Unfortunately, some parts of the new Section 6.5.1 of [RFC3550]. Unfortunately, some parts of the new
algorithms are rather complicated and also produce RTCP CNAMEs which algorithms are rather complicated and also produce RTCP CNAMEs which
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RTCP CNAME for all streams that are to be synchronized. This RTCP CNAME for all streams that are to be synchronized. This
requires a short-term persistent RTCP CNAME that is common across requires a short-term persistent RTCP CNAME that is common across
several RTP streams, and potentially across several related RTP several RTP streams, and potentially across several related RTP
sessions. A common example of such use occurs when lip-syncing audio sessions. A common example of such use occurs when lip-syncing audio
and video streams in a multimedia session, where a single participant and video streams in a multimedia session, where a single participant
has to use the same RTCP CNAME for its audio RTP session and for its has to use the same RTCP CNAME for its audio RTP session and for its
video RTP session. Another example might be to synchronize the video RTP session. Another example might be to synchronize the
layers of a layered audio codec, where the same RTCP CNAME has to be layers of a layered audio codec, where the same RTCP CNAME has to be
used for each layer. used for each layer.
If the multiple RTP streams in an RTP session are not related, thus
do not require synchronization, an RTP endpoint can use different
RTCP CNAMEs for these streams.
A longer-term persistent RTCP CNAME is sometimes useful to facilitate A longer-term persistent RTCP CNAME is sometimes useful to facilitate
third-party monitoring, consistent with [RFC3550]. One such use third-party monitoring, consistent with [RFC3550]. One such use
might be to allow network management tools to correlate the ongoing might be to allow network management tools to correlate the ongoing
quality of service for a participant across multiple RTP sessions for quality of service for a participant across multiple RTP sessions for
fault diagnosis, and to understand long-term network performance fault diagnosis, and to understand long-term network performance
statistics. An application developer that wishes to discourage this statistics. An application developer that wishes to discourage this
type of third-party monitoring can choose to generate a unique RTCP type of third-party monitoring can choose to generate a unique RTCP
CNAME for each RTP session, or group of related RTP sessions, that CNAME for each RTP session, or group of related RTP sessions, that
the application will join. Such a per-session RTCP CNAME cannot be the application will join. Such a per-session RTCP CNAME cannot be
used for traffic analysis, and so provides some limited form of used for traffic analysis, and so provides some limited form of
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