Datagram PLPMTUD for UDP Options
draft-fairhurst-tsvwg-udp-options-dplpmtud-03
Internet Engineering Task Force G. Fairhurst
Internet-Draft T. Jones
Intended status: Standards Track University of Aberdeen
Expires: April 3, 2021 September 30, 2020
Datagram PLPMTUD for UDP Options
draft-fairhurst-tsvwg-udp-options-dplpmtud-03
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. This is a robust method for Path MTU Discovery (PMTUD)
that uses the UDP Options Packetization Layer (PL). It allows a
datagram application that uses this PL, to discover the largest size
of datagram that can be sent across a network path.
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This Internet-Draft will expire on April 3, 2021.
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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 . . . . . . . . . . 5
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 . . . . . . . . . . . . . . . . . . . 9
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. 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] offer calls for applications to receive ICMP
Packet Too Big (PTB) messages and to control the maxmium size of
datagrams that are sent, but does not offer any automated mechanisms
for an application to discover the maximum packet size supported by a
path. Applications and upper layer protocols implement mechanisms
for path MTU discovery above the UDP API.
Packetization Layer PMTUD (PLPMTUD) [RFC4821] describes a method for
a Packetization Layer (PL) (such as UDP with options) to search for
the largest Packetization Layer PMTU (PLPMTU) supported on a path.
Datagram PLPMTUD (DPLPMTUD) [RFC8899] specifies this support for
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