Technical Summary
The User Datagram Protocol (UDP) provides a minimal message-passing
transport that has no inherent congestion control mechanisms. This
document provides guidelines on the use of UDP for the designers of
applications, tunnels and other protocols that use UDP. Congestion
control guidelines are a primary focus, but the document also
provides guidance on other topics, including message sizes,
reliability, checksums, middlebox traversal, the use of ECN, DSCPs,
and ports.
Because congestion control is critical to the stable operation of the
Internet, applications and other protocols that choose to use UDP as
an Internet transport must employ mechanisms to prevent congestion
collapse and to establish some degree of fairness with concurrent
traffic. They may also need to implement additional mechanisms,
depending on how they use UDP.
Some guidance is also applicable to the design of other protocols
(e.g., protocols layered directly on IP or via IP-based tunnels),
especially when these protocols do not themselves provide congestion
control.
This document obsoletes RFC5405 and adds guidelines for multicast UDP
usage.
Working Group Summary
The Transport Area WG (TSVWG) is a collection of people with varied
interests that don't individually justify their own working groups.
This draft is supported by the portion of the TSVWG working group that
is familiar with and interested in UDP and congestion control. The
draft has received significant review and critique from a number of
WG members and has undergone significant modification as a result. A
significant area of expansion over RFC 5405 is the addition of multicast
guidelines; this UDP multicast guideline work began in a separate draft
that was merged into this draft by the WG so that protocol designers
would have one place to look for UDP guidelines.
Recent discussion in the WG has focused on issues related to the
increasing use of UDP to encapsulate other protocols; an important
outcome is the addition of Section 3.6 on Limited Applicability
and Controlled Environments where aspects such as equipment robustness
and operator traffic management may substitute for protocol features
(e.g., checksums, congestion management) that are necessary in
unrestricted environments such as the Internet in general. This
draft incorporates guidelines based on lessons learned from
MPLS/UDP (RFC 7510), GRE/UDP (recent TSVWG WG Last Call) and the
routing area encapsulation design team's work (much broader draft
in the RTGWG WG).
Document Quality
In addition to Last Call reviews by Martin Stiemerling (for TSV-ART),
Ronald Bonica (for RTG-DIR), Paul Kyzivat (for Gen-ART),
Takeshi Takahashi (for SEC-DIR), and Tim Chown (for OPS-DIR),
Mark Allman helped to reconcile protocol timer guidelines in this draft
(for UDP) with the protocol timer guidelines from TCPM (for TCP).
Personnel
Document Shepherd: David Black
Responsible AD: Spencer Dawkins