Stream Control Transmission Protocol

In computer networking, the Stream Control Transmission Protocol (SCTP) is a transport-layer protocol (protocol number 132), serving in a similar role to the popular protocols Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). It provides some of the same service features of both: it is message-oriented like UDP and ensures reliable, in-sequence transport of messages with congestion control like TCP.

The IETF Signaling Transport (SIGTRAN) working group defined the protocol in 2000, and the IETF Transport Area (TSVWG) working group maintains it. RFC 4960 defines the protocol. RFC 3286 provides an introduction.

In the absence of native SCTP support in operating systems it is possible to tunnel SCTP over UDP, as well as mapping TCP API calls to SCTP ones.

Message-based multi-streaming

SCTP applications submit their data to be transmitted in messages (groups of bytes) to the SCTP transport layer. SCTP places messages and control information into separate chunks (data chunks and control chunks), each identified by a chunk header. The protocol can fragment a message into a number of data chunks, but each data chunk contains data from only one user message. SCTP bundles the chunks into SCTP packets. The SCTP packet, which is submitted to the Internet Protocol, consists of a packet header, SCTP control chunks (when necessary), followed by SCTP data chunks (when available).