Deprecating the Generation of IPv6 Atomic Fragments
draft-ietf-6man-deprecate-atomfrag-generation-01

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Document Type Active Internet-Draft (6man WG)
Authors Fernando Gont  , Will LIU  , Tore Anderson 
Last updated 2015-04-27
Stream Internet Engineering Task Force (IETF)
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IPv6 maintenance Working Group (6man)                            F. Gont
Internet-Draft                                    SI6 Networks / UTN-FRH
Updates: 2460, 6145 (if approved)                                 W. Liu
Intended status: Standards Track                     Huawei Technologies
Expires: October 29, 2015                                    T. Anderson
                                                          Redpill Linpro
                                                          April 27, 2015

          Deprecating the Generation of IPv6 Atomic Fragments
            draft-ietf-6man-deprecate-atomfrag-generation-01

Abstract

   The core IPv6 specification requires that when a host receives an
   ICMPv6 "Packet Too Big" message reporting a "Next-Hop MTU" smaller
   than 1280, the host includes a Fragment Header in all subsequent
   packets sent to that destination, without reducing the assumed Path-
   MTU.  The simplicity with which ICMPv6 "Packet Too Big" messages can
   be forged, coupled with the widespread filtering of IPv6 fragments,
   results in an attack vector that can be leveraged for Denial of
   Service purposes.  This document briefly discusses the aforementioned
   attack vector, and formally updates RFC2460 such that generation of
   IPv6 atomic fragments is deprecated, thus eliminating the
   aforementioned attack vector.  Additionally, it formally updates
   RFC6145 such that the Stateless IP/ICMP Translation Algorithm (SIIT)
   does not rely on the generation of IPv6 atomic fragments, thus
   improving the robustness of the protocol.

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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   This Internet-Draft will expire on October 29, 2015.

Gont, et al.            Expires October 29, 2015                [Page 1]
Internet-Draft  Deprecate Generation of IPv6 Atomic Frags     April 2015

Copyright Notice

   Copyright (c) 2015 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Denial of Service (DoS) attack vector . . . . . . . . . . . .   3
   4.  Additional Considerations . . . . . . . . . . . . . . . . . .   5
   5.  Updating RFC2460  . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Updating RFC6145  . . . . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     10.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  Small Survey of OSes that Fail to Produce IPv6
                Atomic Fragments . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   [RFC2460] specifies the IPv6 fragmentation mechanism, which allows
   IPv6 packets to be fragmented into smaller pieces such that they fit
   in the Path-MTU to the intended destination(s).

   Section 5 of [RFC2460] states that, when a host receives an ICMPv6
   "Packet Too Big" message [RFC4443] advertising a "Next-Hop MTU"
   smaller than 1280 (the minimum IPv6 MTU), the host is not required to
   reduce the assumed Path-MTU, but must simply include a Fragment
   Header in all subsequent packets sent to that destination.  The
   resulting packets will thus *not* be actually fragmented into several
   pieces, but rather just include a Fragment Header with both the
   "Fragment Offset" and the "M" flag set to 0 (we refer to these
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