UDP Usage Guidelines

Abstract

The User Datagram Protocol

The Benefits of Using Explicit Congestion Notification (ECN)

“…Both of these are treated by transports as indications of congestion. ECN may also be enabled by other transports: UDP applications that provide congestion control may enable ECN when they are able to correctly process the ECN signals [RFC8085] (e.g., ECN with RTP [RFC6679]). …”

Network Transport Circuit Breakers

“…These applications (e.g., using UDP and its UDP-Lite variant) need to provide appropriate congestion avoidance. Guidance for applications that do not use congestion-controlled transports is provided in [RFC8085]. Such mechanisms can be designed to react on much shorter timescales than a CB, that only observes a traffic envelope.…”

“…One example where a Slow-Trip CB is needed is where flows or trafficaggregates use a tunnel or encapsulation and the flows within the tunnel do not all support TCP-style congestion control (e.g., TCP, SCTP, TFRC), see [RFC8085], Section 3.1.3. A use case is where tunnels are deployed in the general Internet (rather than "controlled environments" within an Internet service provider or enterprise network), especially when the tunnel could need to cross a customer access router.…”

“…Other transports (e.g., using UDP) can employ mechanisms that are sufficient to address congestion on the path [RFC8085]. However, even if the individual flows sharing a tunnel each implement a congestion control mechanism, and individually reduce their transmission rate when network congestion is detected, the overall traffic resulting from the aggregate of the flows does not necessarily avoid persistent congestion.…”

“…This does not imply that it is desirable to provide reliable delivery (e.g., over TCP), since this can incur additional delay in responding to congestion. Appropriate mechanisms could be to duplicate control messages to provide increased robustness to loss and/or to regard a lack of control traffic as an indication that excessive congestion could be being experienced [RFC8085]. If control message traffic is sent over a shared path, it is RECOMMENDED that this control traffic is prioritized to reduce the probability of loss under congestion.…”