Datagram PLPMTUD for UDP Options
draft-fairhurst-tsvwg-udp-options-dplpmtud-02

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Internet Engineering Task Force                             G. Fairhurst
Internet-Draft                                                  T. Jones
Intended status: Standards Track                  University of Aberdeen
Expires: September 10, 2020                                March 9, 2020

                    Datagram PLPMTUD for UDP Options
             draft-fairhurst-tsvwg-udp-options-dplpmtud-02

Abstract

   This document specifies how a UDP Options sender implements Datagram
   Packetization Layer Path Maximum Transmission Unit Discovery
   (DPLPMTUD) as a robust method for Path Maximum Transmission Unit
   Discovery.

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   This Internet-Draft will expire on September 10, 2020.

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Fairhurst & Jones      Expires September 10, 2020               [Page 1]
Internet-Draft                UDPO DPLPMTUD                   March 2020

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  DPLPMTUD for UDP Options  . . . . . . . . . . . . . . . . . .   3
     3.1.  Confirmation of Connectivity across a Path  . . . . . . .   3
     3.2.  Sending UDP-Options Probe Packets . . . . . . . . . . . .   3
       3.2.1.  Sending Packet Probes using the Echo Request Option
               Request Option  . . . . . . . . . . . . . . . . . . .   4
       3.2.2.  Sending Packet Probes that include Application Data .   5
     3.3.  Validating the Path with UDP Options  . . . . . . . . . .   6
       3.3.1.  Sending Packet Probes using Timestamps  . . . . . . .   6
     3.4.  PTB Message Handling for this Method  . . . . . . . . . .   6
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Revision Notes . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The User Datagram Protocol [RFC0768] offers a minimal transport
   service on top of IP and is frequently used as a substrate for other
   protocols.  Applications using UDP frequently have to implement basic
   transport services such as Path Maximum Transmission Unit Discovery
   (PMTUD) themselves.  Section 3.5 of UDP Guidelines [RFC8085]
   recommends that applications implement some form of Path MTU
   Discovery to avoid the generation of IP fragments:

   "Consequently, an application SHOULD either use the path MTU
   information provided by the IP layer or implement Path MTU Discovery
   (PMTUD)".

   The UDP API [RFC8304] offers calls for applications to receive ICMP
   Packet Too Big (PTB) messages and to control the size of messages
   that are sent, but does not offer any automatic mechanisms for an
   application to discover the maximum packet size supported by a path.
   Applications and upper layer protocols are left to implement robust
   PMTUD mechanisms of their own.

   Packetization Layer PMTUD (PLPMTUD) [RFC4821] describes a method for
   a Packetization Layer (such as UDP with options) to search for the
   largest MTU supported on a path in the absence of ICMP PTB messages.
   Datagram PLPMTUD [I-D.ietf-tsvwg-datagram-plpmtud] describes PMTUD