Guidelines for Choosing RTP Control Protocol (RTCP) Canonical Names (CNAMEs)
draft-ietf-avtcore-6222bis-00

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Last updated 2012-12-18
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Network Working Group                                        E. Rescorla
Internet-Draft                                                RTFM, Inc.
Obsoletes:  6222 (if approved)                                  A. Begen
Intended status:  Standards Track                                  Cisco
Expires:  June 21, 2013                                December 18, 2012

          Guidelines for Choosing RTP Control Protocol (RTCP)
                        Canonical Names (CNAMEs)
                     draft-ietf-avtcore-6222bis-00

Abstract

   The RTP Control Protocol (RTCP) Canonical Name (CNAME) is a
   persistent transport-level identifier for an RTP endpoint.  While the
   Synchronization Source (SSRC) identifier of an RTP endpoint may
   change if a collision is detected or when the RTP application is
   restarted, its RTCP CNAME is meant to stay unchanged, so that RTP
   endpoints can be uniquely identified and associated with their RTP
   media streams.

   For proper functionality, RTCP CNAMEs should be unique within the
   participants of an RTP session.  However, the existing guidelines for
   choosing the RTCP CNAME provided in the RTP standard are insufficient
   to achieve this uniqueness.  RFC 6222 was published to update those
   guidelines to allow endpoints to choose unique RTCP CNAMEs.
   Unfortunately, later investigations showed that some parts of the new
   algorithms were unnecessarily complicated and/or ineffective.  This
   document addresses these concerns and replaces RFC 6222.

Status of This Memo

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Copyright Notice

Rescorla & Begen          Expires June 21, 2013                 [Page 1]
Internet-Draft           Choosing an RTCP CNAME            December 2012

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . . . 3
   3.  Deficiencies with Earlier Guidelines for Choosing an RTCP
       CNAME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Choosing an RTCP CNAME  . . . . . . . . . . . . . . . . . . . . 4
     4.1.  Persistent RTCP CNAMEs versus Per-Session RTCP CNAMEs . . . 4
     4.2.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . 5
   5.  Procedure to Generate a Unique Identifier . . . . . . . . . . . 6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
     6.1.  Considerations on Uniqueness of RTCP CNAMEs . . . . . . . . 7
     6.2.  Session Correlation Based on RTCP CNAMEs  . . . . . . . . . 7
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 8

Rescorla & Begen          Expires June 21, 2013                 [Page 2]
Internet-Draft           Choosing an RTCP CNAME            December 2012

1.  Introduction

   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
   endpoint.  However, in practice, some of these methods are not
   guaranteed to produce a unique RTCP CNAME.  [RFC6222] updated the
   guidelines for choosing RTCP CNAMEs, superseding those presented in
   Section 6.5.1 of [RFC3550].  Unfortunately, some parts of the new
   algorithms are rather complicated and also produce RTCP CNAMEs which
   in some cases are potentially linkable over multiple RTCP sessions
   even if a new RTCP CNAME is generated for each session.  This
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