UDPstä

UDPstä is a transport protocol intended to extend the User Datagram Protocol (UDP) by adding optional reliability and ordering while preserving UDP’s low latency. It seeks a middle ground between UDP’s best-effort datagrams and TCP’s guarantees, letting applications enable reliability only for data that needs it. The specification emerged in open-source networking projects and is implemented in several reference stacks. It is not standardized by major bodies and remains experimental in most deployments.

Design and operation: UDPstä preserves the connectionless feel of UDP but adds a compact per-datagram header that carries a version, flags, a sequence number, and a length. There are two modes: an unreliable mode that behaves like UDP, and a reliable mode where the sender repeats lost datagrams and uses acknowledgments to confirm receipt. Ordering is provided within logical streams, and light-weight flow control reduces head-of-line blocking.

Header and security: The header is small, roughly a dozen bytes, with a minimal set of fields to keep latency low. Checksums cover the header and payload. Encryption is not built into UDPstä; privacy is provided by layering DTLS or IPsec. The protocol is designed to work on IPv4 and IPv6 and to facilitate NAT traversal through standard techniques such as keep-alives and connectionless discovery.

Applications and adoption: UDPstä is proposed for low-latency scenarios that can tolerate selective reliability, such as real-time multiplayer games, interactive streaming, and telemetry. It remains experimental and is not widely adopted; many projects prefer established protocols like QUIC, SCTP, or RTP-based stacks. Practically, developers choose the reliability mode per message and weigh latency against delivery guarantees. See also UDP, QUIC, SCTP, DTLS, RTP.