Packetization Layer Path MTU Discovery for Datagram Transports
draft-ietf-tsvwg-datagram-plpmtud-03

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Document Type Active Internet-Draft (tsvwg WG)
Last updated 2018-07-02
Replaces draft-fairhurst-tsvwg-datagram-plpmtud
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Stream WG state WG Document (wg milestone: Apr 2020 - Submit 'Packetizatio... )
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Send notices to Wesley Eddy <wes@mti-systems.com>
Internet Engineering Task Force                             G. Fairhurst
Internet-Draft                                                  T. Jones
Updates: 4821 (if approved)                       University of Aberdeen
Intended status: Standards Track                               M. Tuexen
Expires: January 3, 2019                                    I. Ruengeler
                                 Muenster University of Applied Sciences
                                                           July 02, 2018

     Packetization Layer Path MTU Discovery for Datagram Transports
                  draft-ietf-tsvwg-datagram-plpmtud-03

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.
   This can be used to detect and reduce the message size when a sender
   encounters a network black hole (where packets are discarded, and no
   ICMP message is received).  The method can also probe a network path
   with progressively larger packets to find whether the maximum packet
   size can be increased.  This allows a sender to determine an
   appropriate packet size, providing 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.

   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 https://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

Fairhurst, et al.        Expires January 3, 2019                [Page 1]
Internet-Draft                  DPLPMTUD                       July 2018

   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 January 3, 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
   Provisions Relating to IETF Documents
   (https://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 extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are 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  . . . . . . . . .   5
     1.3.  Path MTU Discovery for Datagram Services  . . . . . . . .   6
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Features Required to Provide Datagram PLPMTUD . . . . . . . .   8
     3.1.  PLPMTU Probe Packets  . . . . . . . . . . . . . . . . . .  10
     3.2.  Validation of Probe Packet Size . . . . . . . . . . . . .  12
     3.3.  Reducing the PLPMTU: Confirming Path Characteristics  . .  12
     3.4.  Increasing the PLPMTU: Supporting Path Changes  . . . . .  13
     3.5.  Robustness to inconsistent Path information . . . . . . .  13
   4.  Datagram Packetization Layer PMTUD  . . . . . . . . . . . . .  13
     4.1.  PROBE_SEARCH: Probing for a larger PLPMTU . . . . . . . .  14
     4.2.  The PROBE_DONE state  . . . . . . . . . . . . . . . . . .  15
     4.3.  Validation and Use of PTB Messages  . . . . . . . . . . .  15
     4.4.  Timers  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     4.5.  Constants . . . . . . . . . . . . . . . . . . . . . . . .  16
     4.6.  Variables . . . . . . . . . . . . . . . . . . . . . . . .  17
     4.7.  Selecting PROBED_SIZE . . . . . . . . . . . . . . . . . .  18
     4.8.  Simple Black Hole Detection . . . . . . . . . . . . . . .  18
       4.8.1.  Simple Black Hole Detection State Machine . . . . . .  19
     4.9.  Full State Machine  . . . . . . . . . . . . . . . . . . .  20
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