Packetization Layer Path MTU Discovery for Datagram Transports
draft-ietf-tsvwg-datagram-plpmtud-01

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Internet Engineering Task Force                             G. Fairhurst
Internet-Draft                                                  T. Jones
Intended status: Standards Track                  University of Aberdeen
Expires: September 6, 2018                                     M. Tuexen
                                                            I. Ruengeler
                                 Muenster University of Applied Sciences
                                                          March 05, 2018

     Packetization Layer Path MTU Discovery for Datagram Transports
                  draft-ietf-tsvwg-datagram-plpmtud-01

Abstract

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

   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
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   Drafts is at http://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
   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 September 6, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Fairhurst, et al.       Expires September 6, 2018               [Page 1]
Internet-Draft              Datagram PLPMTUD                  March 2018

   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
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   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 . . . . . . . .   7
     3.1.  PMTU Probe Packets  . . . . . . . . . . . . . . . . . . .  10
     3.2.  Validation of the Current Effective PMTU  . . . . . . . .  11
     3.3.  Reduction of the Effective PMTU . . . . . . . . . . . . .  11
   4.  Datagram Packetization Layer PMTUD  . . . . . . . . . . . . .  12
     4.1.  Probing . . . . . . . . . . . . . . . . . . . . . . . . .  12
     4.2.  Verification and Use of PTB Messages  . . . . . . . . . .  13
     4.3.  Timers  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     4.4.  Constants . . . . . . . . . . . . . . . . . . . . . . . .  14
     4.5.  Variables . . . . . . . . . . . . . . . . . . . . . . . .  14
     4.6.  Selecting PROBED_SIZE . . . . . . . . . . . . . . . . . .  15
     4.7.  State Machine . . . . . . . . . . . . . . . . . . . . . .  15
   5.  Specification of Protocol-Specific Methods  . . . . . . . . .  18
     5.1.  DPLPMTUD for UDP and UDP-Lite . . . . . . . . . . . . . .  18
       5.1.1.  UDP Options . . . . . . . . . . . . . . . . . . . . .  18
       5.1.2.  UDP Options Required for PLPMTUD  . . . . . . . . . .  18
         5.1.2.1.  Echo Request Option . . . . . . . . . . . . . . .  19
         5.1.2.2.  Echo Response Option  . . . . . . . . . . . . . .  19
       5.1.3.  Sending UDP-Option Probe Packets  . . . . . . . . . .  19
       5.1.4.  Validating the Path with UDP Options  . . . . . . . .  20
       5.1.5.  Handling of PTB Messages by UDP . . . . . . . . . . .  20
     5.2.  DPLPMTUD for SCTP . . . . . . . . . . . . . . . . . . . .  20
       5.2.1.  SCTP/IP4 and SCTP/IPv6  . . . . . . . . . . . . . . .  20
         5.2.1.1.  Sending SCTP Probe Packets  . . . . . . . . . . .  20