A Widely-Deployed Solution To The Generic Routing Encapsulation (GRE) Fragmentation Problem
draft-ietf-intarea-gre-mtu-01

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Last updated 2015-04-08 (latest revision 2014-12-30)
Replaces draft-bonica-intarea-gre-mtu
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Intarea Working Group                                          R. Bonica
Internet-Draft                                          Juniper Networks
Intended status: Informational                              C. Pignataro
Expires: July 3, 2015                                      Cisco Systems
                                                                J. Touch
                                                                 USC/ISI
                                                       December 30, 2014

 A Widely-Deployed Solution To The Generic Routing Encapsulation (GRE)
                         Fragmentation Problem
                     draft-ietf-intarea-gre-mtu-01

Abstract

   This memo describes how many vendors have solved the Generic Routing
   Encapsulation (GRE) fragmentation problem.  The solution described
   herein is configurable.  It is widely deployed on the Internet in its
   default configuration.

Status of This Memo

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   This Internet-Draft will expire on July 3, 2015.

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   Copyright (c) 2014 IETF Trust and the persons identified as the
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Bonica, et al.            Expires July 3, 2015                  [Page 1]
Internet-Draft              GRE Fragmentation              December 2014

   include Simplified BSD License text as described in Section 4.e of
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Solutions . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  RFC 4459 Solutions  . . . . . . . . . . . . . . . . . . .   4
     2.2.  A Widely-Deployed Solution  . . . . . . . . . . . . . . .   4
   3.  Implementation Details  . . . . . . . . . . . . . . . . . . .   5
     3.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  GRE MTU (GMTU) Estimation and Discovery . . . . . . . . .   5
     3.3.  GRE Ingress Node Procedures . . . . . . . . . . . . . . .   6
       3.3.1.  Procedures Affecting the GRE Payload  . . . . . . . .   6
       3.3.2.  Procedures Affecting The GRE Deliver Header . . . . .   7
     3.4.  GRE Egress Node Procedures  . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Generic Routing Encapsulation (GRE) [RFC2784] [RFC2890] 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 in
   the Internet.

   The GRE specification does not describe fragmentation procedures.
   Lacking guidance from the specification, vendors have developed
   implementation-specific fragmentation solutions.  A GRE tunnel will
   operate correctly only if its ingress and egress nodes support
   compatible fragmentation solutions.  [RFC4459] describes several
   fragmentation solutions and evaluates their relative merits.

   This memo reviews the fragmentation solutions presented in [RFC4459].
   It also describes how many vendors have solved the GRE fragmentation
   problem.  The solution described herein is configurable, and has been
   widely deployed in its default configuration.

   This memo addresses point-to-point unicast GRE tunnels that carry
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