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IPv6 and UDP Checksums for Tunneled Packets
RFC 6935

Internet Engineering Task Force (IETF)                        M. Eubanks
Request for Comments: 6935                            AmericaFree.TV LLC
Updates: 2460                                                P. Chimento
Category: Standards Track               Johns Hopkins University Applied
ISSN: 2070-1721                                       Physics Laboratory
                                                           M. Westerlund
                                                                Ericsson
                                                              April 2013

              IPv6 and UDP Checksums for Tunneled Packets

Abstract

   This document updates the IPv6 specification (RFC 2460) to improve
   performance when a tunnel protocol uses UDP with IPv6 to tunnel
   packets.  The performance improvement is obtained by relaxing the
   IPv6 UDP checksum requirement for tunnel protocols whose header
   information is protected on the "inner" packet being carried.
   Relaxing this requirement removes the overhead associated with the
   computation of UDP checksums on IPv6 packets that carry the tunnel
   protocol packets.  This specification describes how the IPv6 UDP
   checksum requirement can be relaxed when the encapsulated packet
   itself contains a checksum.  It also describes the limitations and
   risks of this approach and discusses the restrictions on the use of
   this method.

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/rfc6935.

Eubanks, et al.              Standards Track                    [Page 1]
RFC 6935         IPv6/UDP Checksums for Tunneled Packets      April 2013

Copyright Notice

   Copyright (c) 2013 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
     2.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   3.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Discussion . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     4.1.  Analysis of Corruption in Tunnel Context . . . . . . . . .  5
     4.2.  Limitation to Tunnel Protocols . . . . . . . . . . . . . .  7
     4.3.  Middleboxes  . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  The Zero UDP Checksum Update . . . . . . . . . . . . . . . . .  9
   6.  Additional Observations  . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11

Eubanks, et al.              Standards Track                    [Page 2]
RFC 6935         IPv6/UDP Checksums for Tunneled Packets      April 2013

1.  Introduction

   This document constitutes an update of the IPv6 specification
   [RFC2460] for cases where a tunnel protocol uses UDP with IPv6 to
   tunnel packets.  With the rapid growth of the Internet, tunnel
   protocols have become increasingly important to enable the deployment
   of new protocols.  Tunnel protocols can be deployed rapidly, while
   the time to upgrade and deploy a new protocol on a critical mass of
   routers, middleboxes, and hosts on the global Internet is now
   measured in decades.  At the same time, the increasing use of
   firewalls and other security-related middleboxes means that truly new
   tunnel protocols, with new protocol numbers, are also unlikely to be

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