Packetization Layer Path MTU Discovery (PLMTUD) For UDP Transports Using Session Traversal Utilities for NAT (STUN)
draft-ietf-tram-stun-pmtud-17
TRAM M. Petit-Huguenin
Internet-Draft Impedance Mismatch
Intended status: Standards Track G. Salgueiro
Expires: January 7, 2021 F. Garrido
Cisco
July 6, 2020
Packetization Layer Path MTU Discovery (PLMTUD) For UDP Transports Using
Session Traversal Utilities for NAT (STUN)
draft-ietf-tram-stun-pmtud-17
Abstract
The datagram exchanged between two Internet endpoints have to go
through a series of physical and virtual links that may have
different limits on the upper size of the datagram they can transmit
without fragmentation. Because fragmentation is considered harmful,
most transports and protocols are designed with a mechanism that
permits dynamic measurement of the maximum size of a datagram. This
mechanism is called Packetization Layer Path MTU Discovery (PLPMTUD).
But the UDP transport and some of the protocols that use UDP were
designed without that feature. The Session Traversal Utilities for
NAT (STUN) Usage described in this document permits retrofitting an
existing UDP-based protocol with such a feature. Similarly, a new
UDP-based protocol could simply reuse the mechanism described in this
document.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 7, 2021.
Petit-Huguenin, et al. Expires January 7, 2021 [Page 1]
Internet-Draft STUN PMTUD July 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Overview of Operations . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Probing Mechanisms . . . . . . . . . . . . . . . . . . . . . 6
4.1. Simple Probing Mechanism . . . . . . . . . . . . . . . . 7
4.1.1. Sending a Probe Request . . . . . . . . . . . . . . . 7
4.1.2. Receiving a Probe Request . . . . . . . . . . . . . . 8
4.1.3. Receiving a Probe Response . . . . . . . . . . . . . 8
4.2. Complete Probing Mechanism . . . . . . . . . . . . . . . 8
4.2.1. Sending a Probe Indications and Report Request . . . 9
4.2.2. Receiving an ICMP Packet . . . . . . . . . . . . . . 9
4.2.3. Receiving a Probe Indication and Report Request . . . 9
4.2.4. Receiving a Report Response . . . . . . . . . . . . . 10
4.2.5. Using Checksums as Packet Identifiers . . . . . . . . 10
4.2.6. Using Sequence Numbers as Packet Identifiers . . . . 11
5. Probe Support Signaling Mechanisms . . . . . . . . . . . . . 12
5.1. Explicit Probe Support Signaling Mechanism . . . . . . . 12
5.2. Implicit Probe Support Signaling Mechanism . . . . . . . 13
6. STUN Attributes . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. IDENTIFIERS . . . . . . . . . . . . . . . . . . . . . . . 13
6.2. PMTUD-SUPPORTED . . . . . . . . . . . . . . . . . . . . . 13
6.3. PADDING . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. DPLPMTUD Considerations . . . . . . . . . . . . . . . . . . . 14
7.1. Features Required to provide Datagram PLPMTUD . . . . . . 14
7.2. Application Support for DPLPMTUD with UDP . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
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