Generic Routing Encapsulation (GRE) Fragmentation Strategy
draft-bonica-intarea-gre-mtu-00

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Replaced by rfc7588, draft-ietf-intarea-gre-mtu
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Intarea Working Group                                          R. Bonica
Internet-Draft                                          Juniper Networks
Intended status: Best Current Practice                      May 29, 2013
Expires: November 30, 2013

       Generic Routing Encapsulation (GRE) Fragmentation Strategy
                    draft-bonica-intarea-gre-mtu-00

Abstract

   This memo documents a GRE fragmentation strategy upon which many
   vendors have converged.  Specifically, it defines procedures to be
   executed by GRE ingress routers.  It is published so that those
   building new implementations will be aware of best common practice.
   It is also published so that those building applications over GRE
   will understand how GRE works.

Requirements Language

   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 RFC 2119 [RFC2119].

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 30, 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

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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   described in the Simplified BSD License.

Table of Contents

   1.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  How To Use This Document  . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Design Goals  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Common Procedures . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Tunnel MTU (TMTU) Discovery . . . . . . . . . . . . . . .   5
   4.  Procedures Affecting The GRE Deliver Header . . . . . . . . .   5
     4.1.  Tunneling GRE Over IPv4 . . . . . . . . . . . . . . . . .   5
     4.2.  Tunneling GRE Over IPv6 . . . . . . . . . . . . . . . . .   6
   5.  Procedures Affecting the GRE Payoad . . . . . . . . . . . . .   6
     5.1.  IPv4 Payloads . . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  IPv6 Payloads . . . . . . . . . . . . . . . . . . . . . .   6
     5.3.  MPLS Payloads . . . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
     7.1.  VPN Considerations  . . . . . . . . . . . . . . . . . . .   7
     7.2.  Attacks Against PMTU Discovery  . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Problem Statement

   Generic Routing Encapsulation (GRE) [RFC2784] can be used to carry
   any network layer protocol over any network layer protocol.  GRE has
   been implemented by many vendors and is widely deployed on the
   Internet.

   [RFC2784], by design, does not describe procedures that affect
   fragmentation.  Lacking guidance from the specification, vendors have
   developed implementation-specific fragmentation strategies.  For the
   most part, devices implementing one fragmentation strategy
   interoperate with devices that implement another fragmentation
   strategy.

   However, implementors and network operators have discovered that some
   fragmentation strategies work better than others.  A poorly chosen

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