Packetization Layer Path MTU Discovery for Datagram Transports
draft-ietf-tsvwg-datagram-plpmtud-02

Document Type Active Internet-Draft (tsvwg WG)
Last updated 2018-06-07
Replaces draft-fairhurst-tsvwg-datagram-plpmtud
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Internet Engineering Task Force                             G. Fairhurst
Internet-Draft                                                  T. Jones
Updates: 4821 (if approved)                       University of Aberdeen
Intended status: Standards Track                               M. Tuexen
Expires: December 08, 2018                                  I. Ruengeler
                                 Muenster University of Applied Sciences
                                                           June 08, 2018

     Packetization Layer Path MTU Discovery for Datagram Transports
                  draft-ietf-tsvwg-datagram-plpmtud-02

Abstract

   This document describes a robust method for Path MTU Discovery
   (PMTUD) for datagram Packetization layers.  The document describes an
   extension to RFC 1191 and RFC 8201, which specifies ICMP-based Path
   MTU Discovery for IPv4 and IPv6. The method allows a Packetization
   Layer (PL), or a datagram application that uses a PL, to discover
   whether a network path can support the current size of datagram and
   to probe a network path with progressively larger packets to find
   whether the maxium packet size can be increased.  This allows a
   sender to determine an appropriate packet size.  This provides
   functionally for datagram transports that is equivalent to the
   Packetization layer PMTUD specification for TCP, specified in
   RFC4821.

   The document also provides implementation notes for incorporating
   Datagram PMTUD into IETF Datagram transports or applications that use
   transports.

   When published, this specification updates RFC4821.

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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Fairhurst, Jones, TuexeExpiresnDecember 08, 2018                [Page 1]
Internet-Draft                  DPLPMTUD                       June 2018

   This Internet-Draft will expire on December 08, 2018.

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
   Provisions Relating to IETF Documents (http://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Classical Path MTU Discovery . . . . . . . . . . . . . . .  3
     1.2.  Packetization Layer Path MTU Discovery . . . . . . . . . .  4
     1.3.  Path MTU Discovery for Datagram Services . . . . . . . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Features Required to Provide Datagram PLPMTUD  . . . . . . . .  8
     3.1.  PLPMTU Probe Packets . . . . . . . . . . . . . . . . . . . 10
     3.2.  Validation of Probe Packet Size  . . . . . . . . . . . . . 11
     3.3.  Reducing the PLPMTU: Confirming Path Characteristics . . . 12
     3.4.  Increasing the PLPMTU: Supporting Path Changes . . . . . . 12
     3.5.  Robustness to inconsistent Path information  . . . . . . . 12
   4.  Datagram Packetization Layer PMTUD . . . . . . . . . . . . . . 13
     4.1.  PROBE_SEARCH: Probing for a larger PLPMTU  . . . . . . . . 13
     4.2.  The PROBE_DONE state . . . . . . . . . . . . . . . . . . . 14
     4.3.  Verification and Use of PTB Messages . . . . . . . . . . . 14
     4.4.  Timers . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     4.5.  Constants  . . . . . . . . . . . . . . . . . . . . . . . . 15
     4.6.  Variables  . . . . . . . . . . . . . . . . . . . . . . . . 16
     4.7.  Selecting PROBED_SIZE  . . . . . . . . . . . . . . . . . . 16
     4.8.  Black Hole Detection . . . . . . . . . . . . . . . . . . . 17
     4.9.  State Machine  . . . . . . . . . . . . . . . . . . . . . . 17
   5.  Specification of Protocol-Specific Methods . . . . . . . . . . 20
     5.1.  Application support for DPLPMTUD with UDP or UDP-Lite  . . 20
       5.1.1.  Application Request  . . . . . . . . . . . . . . . . . 20
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