IPv6 Minimum Path MTU Hop-by-Hop Option
draft-hinden-6man-mtu-option-00

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Last updated 2018-10-16
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Network Working Group                                          R. Hinden
Internet-Draft                                      Check Point Software
Intended status: Standards Track                            G. Fairhurst
Expires: April 19, 2019                           University of Aberdeen
                                                        October 16, 2018

                IPv6 Minimum Path MTU Hop-by-Hop Option
                    draft-hinden-6man-mtu-option-00

Abstract

   This document specifies a new Hop-by-Hop IPv6 option that is used to
   record the minimum Path MTU from a source to a destination host.
   This collects a minimum recorded MTU along the path to the
   destination.  The value can then be communicated back to the source
   host by an ICMPv6 Packet Too Big message.

   This Hop-by-Hop option is intended to be used in environments like
   Data Centers and on paths between Data Centers, to allow them to
   better take advantage of paths able to support a large Path MTU.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on April 19, 2019.

Copyright Notice

   Copyright (c) 2018 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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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

Hinden & Fairhurst       Expires April 19, 2019                 [Page 1]
Internet-Draft               Path MTU Option                October 2018

   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   4
   3.  Applicability Statements  . . . . . . . . . . . . . . . . . .   4
   4.  IPv6 Minimum Path MTU Hop-by-Hop Option . . . . . . . . . . .   4
   5.  Router, Host, and Transport Behaviors . . . . . . . . . . . .   5
     5.1.  Router Behaviour  . . . . . . . . . . . . . . . . . . . .   5
     5.2.  Host Behavior . . . . . . . . . . . . . . . . . . . . . .   5
     5.3.  Transport Behavior  . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   9.  Change log [RFC Editor: Please remove]  . . . . . . . . . . .   9
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   9
     10.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   This draft proposes a new Hop-by-Hop Option to be used to record the
   minimum MTU along a path between the source and destination nodes.
   The source node creates a packet with this Hop-by-Hop Option and
   fills the Reported PMTU Field in the option with the MTU of the
   outbound link that will be used to forward the the packet towards the
   destination.

   At each subsequent hop where the option is processed, the router
   compares the value of the Reported PMTU in the option and the MTU of
   its outgoing link.  If the MTU of the outgoing link is less than the
   Reported PMTU specified in the option, it rewrites the value in the
   Option Data with the smaller value.  When the packet arrives at the
   Destination node, the Destination node can send the minimum reported
   PMTU value back to the Source Node.  This can be done by creating an
   ICMPv6 Packet Too Big message.

   The figure below can be used to illustrate the operation of the
   method.  In this case, the path between the Sender and Destination
   nodes comprises three links, the sender has a link MTU of size MTU-S,
   the link between routers R1 and R2 has an MTU of size 8 KBytes, and
   the final link to the destination has an MTU of size MTU-D.
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