UDP or User Datagram Protocol is a core protocol on the internet popular in real-time and lossy applications such as gaming and media streaming. †UDP Forwarding can be configured on the services Ports page.
Domain Name Servers (DNS)
Video Streaming application
Chat servers (but not IRC)
UDP sessions, where a session is defined by a guaranteed of a constant local endpoint is only guaranteed for 10 minutes. Under some situations such as where over 10,000 new connections are initiated this may be reduced.
A maximum connection limitation of 20,000 connections (unique clients) exists for implementation reasons, connections will be recycled in a Least Recently Used (LRU) manner