One document matched: draft-begen-avt-rtp-cnames-00.txt

AVT                                                             A. Begen
Internet-Draft                                                     Cisco
Updates:  3550 (if approved)                                  C. Perkins
Intended status:  Standards Track                  University of Glasgow
Expires:  October 16, 2010                                April 14, 2010


 Guidelines for Choosing an RTP Control Protocol (RTCP) Canonical Name
              (CNAME) for Hosts with Private IP Addresses
                     draft-begen-avt-rtp-cnames-00

Abstract

   The RTP Control Protocol (RTCP) Canonical Name (CNAME) is a
   persistent transport-level identifier for an RTP endpoint.  While the
   Synchronisation Source (SSRC) identifier of an RTP endpoint may
   change if a collision is detected, or when the RTP application is
   restarted, the CNAME is meant to stay unchanged, so that RTP
   endpoints can be uniquely identified and associated with their RTP
   media streams.  For proper functionality, CNAMEs should be unique
   within the participants of an RTP session.  The recommendations for
   choice of the RTCP CNAME provided in RFC 3550 are insufficient to
   achieve uniqueness in some environments, particularly private IP
   networks.  This memo updates the guidelines in RFC 3550 to allow
   endpoints to choose unique CNAMEs in these environments.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 16, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   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
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   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.  Requirements Notation . . . . . . . . . . . . . . . . . . . . . 3
   3.  Choice of RTCP CNAME in Private Networks  . . . . . . . . . . . 3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 4































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1.  Introduction

   In Section 6.5.1 of [RFC3550], there are a number of recommendations
   for choosing the RTCP CNAME for an RTP endpoint.  These recommend
   that the CNAME is of the form "user@host" for multiuser systems, or
   "host" if the username is not available.  The "host" part is
   specified to be the fully qualified domain name of the host from
   which the real-time data originates, or the numeric representation of
   the IP address of the interface from which the RTP data originates
   for hosts that do not have a domain name.

   As noted in [RFC3550], the use of private network address space
   (e.g., 10.0.0.0/8) can result in hosts having network addresses that
   are not globally unique, and can lead to non-unique CNAMEs if hosts
   with private addresses and no direct IP connectivity to the public
   Internet have their RTP packets forwarded to the public Internet
   through an RTP-level translator.  [RFC3550] suggests that such
   applications provide a configuration option to allow the user to
   choose a unique CNAME, and puts the burden on the translator to
   translate CNAMEs from private addresses to public addresses if
   necessary to keep private addresses from being exposed.  Experience
   has shown that this does not work in practice, therefore this memo
   proposes an alternate algorithm for CNAME choice in private networks.


2.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


3.  Choice of RTCP CNAME in Private Networks

   In private IP networks, using the numeric representation of the
   private IP address as the RTCP CNAME is NOT RECOMMENDED, since it
   results in RTCP CNAMEs that are not globally unique.

   A host that does not know its fully qualified domain name, and is
   configured with a private IP address on the interface it is using for
   RTP communication, SHOULD use the numeric representation of the
   layer-2 (MAC) address of the interface it is using for RTP
   communication as the "host" part of its CNAME.  For IEEE 802 MAC
   addresses, such as Ethernet, the standard colon-separated hexadecimal
   format is to be used, e.g., "00:23:32:af:9b:aa".






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4.  Security Considerations

   The security considerations of [RFC3550] apply to this document as
   well.


5.  IANA Considerations

   There are no IANA considerations in this document.


6.  Normative References

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, July 2003.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.


Authors' Addresses

   Ali Begen
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email:  abegen@cisco.com


   Colin Perkins
   University of Glasgow
   Department of Computing Science
   Glasgow,   G12 8QQ
   UK

   Email:  csp@csperkins.org












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