IPv6 Minimum Path MTU Hop-by-Hop Option
draft-ietf-6man-mtu-option-01

Document Type Active Internet-Draft (6man WG)
Last updated 2019-09-13
Replaces draft-hinden-6man-mtu-option
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Network Working Group                                          R. Hinden
Internet-Draft                                      Check Point Software
Intended status: Experimental                               G. Fairhurst
Expires: March 16, 2020                           University of Aberdeen
                                                      September 13, 2019

                IPv6 Minimum Path MTU Hop-by-Hop Option
                     draft-ietf-6man-mtu-option-01

Abstract

   This document specifies a new Hop-by-Hop IPv6 option that is used to
   record the minimum Path MTU along the forward path between a source
   host 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 using the return Path MTU field in
   the option.

   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.

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

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   This Internet-Draft will expire on March 16, 2020.

Copyright Notice

   Copyright (c) 2019 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

Hinden & Fairhurst       Expires March 16, 2020                 [Page 1]
Internet-Draft               Path MTU Option              September 2019

   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.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Motivation and Problem Solved . . . . . . . . . . . . . . . .   4
   3.  Requirements Language . . . . . . . . . . . . . . . . . . . .   5
   4.  Applicability Statements  . . . . . . . . . . . . . . . . . .   5
   5.  IPv6 Minimum Path MTU Hop-by-Hop Option . . . . . . . . . . .   5
   6.  Router, Host, and Transport Behaviors . . . . . . . . . . . .   6
     6.1.  Router Behaviour  . . . . . . . . . . . . . . . . . . . .   6
     6.2.  Host Behavior . . . . . . . . . . . . . . . . . . . . . .   7
     6.3.  Transport Behavior  . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   10. Change log [RFC Editor: Please remove]  . . . . . . . . . . .  11
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  Planned Experiments  . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   This draft proposes a new Hop-by-Hop Option to be used to record the
   minimum MTU along the forward path between the source and destination
   hosts.  The source host creates a packet with this Hop-by-Hop Option
   and fills the Reported PMTU Field in the option with the value of the
   MTU for the outbound link that will be used to forward 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 host, the destination host can send the minimum reported
   PMTU value back to the source host using the Return PMTU field in the
   option.

   The figure below can be used to illustrate the operation of the
   method.  In this case, the path between the source and destination
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