UDP, defined in RFC 768 (August 1980), is a thin envelope around IP that adds only source/destination ports and a checksum. It does not retransmit, does not order packets, does not adapt its rate. Everything else — reliability, congestion control, encryption — has to be built on top by the application. That apparent weakness is the whole point: by leaving those decisions to the application, UDP lets streaming protocols make different tradeoffs than HTTP does.
In streaming, UDP is the substrate for everything that needs low latency or selective reliability. SRT and RIST build adaptive retransmit windows on top of UDP for contribution; WebRTC's media path uses SRTP over UDP and tolerates packet loss to avoid the wait of retransmission; QUIC (RFC 9000, May 2021) implements its own ordered, reliable streams over UDP and serves HTTP/3. The 2026 trend is that more and more of the streaming stack quietly moves to UDP underneath while keeping a familiar API on top.
The operational catch with UDP is firewalls. Many corporate and ISP networks rate-limit or block arbitrary UDP, and almost all NATs handle UDP differently from TCP. A WebRTC or QUIC pipeline must include fallback to TCP-based alternatives (TURN over TCP/443, HTTP/2 fallback for QUIC) for the percentage of users whose network silently kills UDP.
The book · Volume 2 of 7
Video Streaming: A Complete Guide to Video Delivery: From Network Protocols and Transport to Ingest, HLS, and MPEG-DASH
UDP gives streaming protocols control over timing, which is why QUIC, SRT, RIST and WebRTC build on it, but it also leaves loss recovery and congestion control to the application. This volume covers UDP in detail, with TCP versus UDP, packet loss, congestion control, NAT behaviour and QUIC. Written by Nikolay Sapunov, CEO at Fora Soft.
Deciding whether UDP-based transport is worth it for your streams?
Describe your networks and latency targets and we will return a transport recommendation comparing UDP-based options with TCP, with loss and latency numbers. 250+ video products shipped since 2005.
