Port Mapping between Unicast and Multicast RTP Sessions
RFC 6284

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Internet Engineering Task Force (IETF)                          A. Begen
Request for Comments: 6284                                       D. Wing
Category: Standards Track                                          Cisco
ISSN: 2070-1721                                          T. Van Caenegem
                                                          Alcatel-Lucent
                                                               June 2011

        Port Mapping between Unicast and Multicast RTP Sessions

Abstract

   This document presents a port mapping solution that allows RTP
   receivers to choose their own ports for an auxiliary unicast session
   in RTP applications using both unicast and multicast services.  The
   solution provides protection against denial-of-service or packet
   amplification attacks that could be used to cause one or more RTP
   packets to be sent to a victim client.

Status of This Memo

   This is an Internet Standards Track document.

   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).  Further information on
   Internet Standards is available in 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/rfc6284.

Copyright Notice

   Copyright (c) 2011 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.

Begen, et al.                Standards Track                    [Page 1]
RFC 6284                      Port Mapping                     June 2011

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements Notation  . . . . . . . . . . . . . . . . . . . .  4
   3.  Token-Based Port Mapping . . . . . . . . . . . . . . . . . . .  5
     3.1.  Motivating Scenario  . . . . . . . . . . . . . . . . . . .  6
     3.2.  Normative Behavior and Requirements  . . . . . . . . . . .  9
   4.  Message Formats  . . . . . . . . . . . . . . . . . . . . . . . 11
     4.1.  Port Mapping Request . . . . . . . . . . . . . . . . . . . 12
     4.2.  Port Mapping Response  . . . . . . . . . . . . . . . . . . 13
     4.3.  Token Verification Request . . . . . . . . . . . . . . . . 15
       4.3.1.  Where to Include Token . . . . . . . . . . . . . . . . 16
     4.4.  Token Verification Failure . . . . . . . . . . . . . . . . 17
   5.  Procedures for Token Construction  . . . . . . . . . . . . . . 18
   6.  Validating Tokens  . . . . . . . . . . . . . . . . . . . . . . 20
   7.  SDP Signaling  . . . . . . . . . . . . . . . . . . . . . . . . 21
     7.1.  The 'portmapping-req' Attribute  . . . . . . . . . . . . . 21
       7.1.1.  ABNF Definition of 'portmapping-req' . . . . . . . . . 21
       7.1.2.  Offer/Answer Model Considerations  . . . . . . . . . . 22
     7.2.  Requirements . . . . . . . . . . . . . . . . . . . . . . . 22
     7.3.  Example and Discussion . . . . . . . . . . . . . . . . . . 23
   8.  Address Pooling NATs . . . . . . . . . . . . . . . . . . . . . 24
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 24
     9.1.  Tokens . . . . . . . . . . . . . . . . . . . . . . . . . . 24
     9.2.  The 'portmapping-req' Attribute  . . . . . . . . . . . . . 26
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 26
     10.1. Registration of SDP Attributes . . . . . . . . . . . . . . 26
     10.2. Registration of RTCP Control Packet Types  . . . . . . . . 27
     10.3. SMT Values for TOKEN Packet Type Registry  . . . . . . . . 27
     10.4. RAMS Response Code Space Registry  . . . . . . . . . . . . 27
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 28
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 28
     12.2. Informative References . . . . . . . . . . . . . . . . . . 29

Begen, et al.                Standards Track                    [Page 2]
RFC 6284                      Port Mapping                     June 2011

1.  Introduction

   In (any-source or source-specific) multicast RTP applications,
   destination ports (i.e., the ports on which the multicast receivers