UDP Usage Guidelines: (Replaces RFC 5405)

The User Datagram Protocol (UDP) provides a minimal message-passing
transport that has no inherent congestion control mechanisms.
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.

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, and middlebox traversal.