Packetization Layer Path MTU Discovery for Datagram Transports
draft-ietf-tsvwg-datagram-plpmtud-14

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Internet Engineering Task Force                             G. Fairhurst
Internet-Draft                                                  T. Jones
Updates: 4821, 4960, 8085 (if approved)           University of Aberdeen
Intended status: Standards Track                               M. Tuexen
Expires: 15 August 2020                                     I. Ruengeler
                                                              T. Voelker
                                 Muenster University of Applied Sciences
                                                        12 February 2020

     Packetization Layer Path MTU Discovery for Datagram Transports
                  draft-ietf-tsvwg-datagram-plpmtud-14

Abstract

   This document describes a robust method for Path MTU Discovery
   (PMTUD) for datagram Packetization Layers (PLs).  It describes an
   extension to RFC 1191 and RFC 8201, which specifies ICMP-based Path
   MTU Discovery for IPv4 and IPv6.  The method allows a 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 packet
   black hole (where packets are discarded).  The method can probe a
   network path with progressively larger packets to discover whether
   the maximum packet size can be increased.  This allows a sender to
   determine an appropriate packet size, providing functionality for
   datagram transports that is equivalent to the Packetization Layer
   PMTUD specification for TCP, specified in RFC 4821.

   The document updates RFC 4821 to specify the method for datagram PLs,
   and updates RFC 8085 as the method to use in place of RFC 4821 with
   UDP datagrams.  Section 7.3 of RFC4960 recommends an endpoint apply
   the techniques in RFC4821 on a per-destination-address basis.
   RFC4960 is updated to recommend that SCTP uses the method specified
   in this document instead of the method in RFC4821.

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

   When published, this specification updates RFC 4821 and RFC 8085.

Status of This Memo

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

Fairhurst, et al.        Expires 15 August 2020                 [Page 1]
Internet-Draft                  DPLPMTUD                   February 2020

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 15 August 2020.

Copyright Notice

   Copyright (c) 2020 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  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Classical Path MTU Discovery  . . . . . . . . . . . . . .   4
     1.2.  Packetization Layer Path MTU Discovery  . . . . . . . . .   6
     1.3.  Path MTU Discovery for Datagram Services  . . . . . . . .   7
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   8
   3.  Features Required to Provide Datagram PLPMTUD . . . . . . . .  10
   4.  DPLPMTUD Mechanisms . . . . . . . . . . . . . . . . . . . . .  13
     4.1.  PLPMTU Probe Packets  . . . . . . . . . . . . . . . . . .  13
     4.2.  Confirmation of Probed Packet Size  . . . . . . . . . . .  14
     4.3.  Black Hole Detection  . . . . . . . . . . . . . . . . . .  15
     4.4.  The Maximum Packet Size (MPS) . . . . . . . . . . . . . .  15
     4.5.  Disabling the Effect of PMTUD . . . . . . . . . . . . . .  16
     4.6.  Response to PTB Messages  . . . . . . . . . . . . . . . .  17
       4.6.1.  Validation of PTB Messages  . . . . . . . . . . . . .  17
       4.6.2.  Use of PTB Messages . . . . . . . . . . . . . . . . .  18
   5.  Datagram Packetization Layer PMTUD  . . . . . . . . . . . . .  19