DCCP-UDP: A Datagram Congestion Control Protocol UDP Encapsulation for NAT Traversal
RFC 6773

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Internet Engineering Task Force (IETF)                         T. Phelan
Request for Comments: 6773                                         Sonus
Updates: 4340, 5762                                         G. Fairhurst
Category: Standards Track                         University of Aberdeen
ISSN: 2070-1721                                               C. Perkins
                                                   University of Glasgow
                                                           November 2012

 DCCP-UDP: A Datagram Congestion Control Protocol UDP Encapsulation for
                             NAT Traversal

Abstract

   This document specifies an alternative encapsulation of the Datagram
   Congestion Control Protocol (DCCP), referred to as DCCP-UDP.  This
   encapsulation allows DCCP to be carried through the current
   generation of Network Address Translation (NAT) middleboxes without
   modification of those middleboxes.  This document also updates the
   Session Description Protocol (SDP) information for DCCP defined in
   RFC 5762.

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/rfc6773.

Phelan, et al.               Standards Track                    [Page 1]
RFC 6773                 DCCP-UDP Encapsulation            November 2012

Copyright Notice

   Copyright (c) 2012 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.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  DCCP-UDP . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  The UDP Header . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  The DCCP Generic Header  . . . . . . . . . . . . . . . . .  5
     3.3.  DCCP-UDP Checksum Procedures . . . . . . . . . . . . . . .  6
       3.3.1.  Partial Checksums and the Minimum Checksum
               Coverage Feature . . . . . . . . . . . . . . . . . . .  7
     3.4.  Network-Layer Options  . . . . . . . . . . . . . . . . . .  8
     3.5.  Explicit Congestion Notification . . . . . . . . . . . . .  8
     3.6.  ICMP Handling for Messages Relating to DCCP-UDP  . . . . .  8
     3.7.  Path Maximum Transmission Unit Discovery . . . . . . . . .  9
     3.8.  Usage of the UDP Port by DCCP-UDP  . . . . . . . . . . . .  9
     3.9.  Service Codes and the DCCP Port Registry . . . . . . . . . 11
   4.  DCCP-UDP and Higher-Layer Protocols  . . . . . . . . . . . . . 11
     5.1.  Protocol Identification  . . . . . . . . . . . . . . . . . 12
     5.2.  Signalling Encapsulated DCCP Ports . . . . . . . . . . . . 13
     5.3.  Connection Management  . . . . . . . . . . . . . . . . . . 14
     5.4.  Negotiating the DCCP-UDP Encapsulation versus Native
           DCCP . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     5.5.  Example of SDP Use . . . . . . . . . . . . . . . . . . . . 15
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
     7.1.  UDP Port Allocation  . . . . . . . . . . . . . . . . . . . 17
     7.2.  DCCP Reset . . . . . . . . . . . . . . . . . . . . . . . . 17
     7.3.  SDP Attribute Allocation . . . . . . . . . . . . . . . . . 17
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 18
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 18
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 18

Phelan, et al.               Standards Track                    [Page 2]
RFC 6773                 DCCP-UDP Encapsulation            November 2012

1.  Introduction

   The Datagram Congestion Control Protocol (DCCP) [RFC4340] is a
   transport-layer protocol that provides upper layers with the ability