DCCP

DCCP, or Datagram Congestion Control Protocol, is a transport layer protocol of the Internet Protocol Suite. It provides a connection-oriented, datagram-based service that includes built-in mechanisms for congestion control. Unlike TCP, DCCP does not guarantee reliable delivery or in-order arrival, making it suitable for applications that can tolerate packet loss but require controlled data flow and responsiveness.

Designed for applications such as streaming media, video conferencing, and interactive gaming, DCCP aims to combine low latency with congestion-aware transmission. A DCCP connection begins with a two-way handshake to establish the session and negotiate parameters, including the Congestion Control Identifier (CCID), which selects the congestion control algorithm to be used. Data is transmitted as datagrams over the established connection and is subject to loss, reordering, and throttling by the chosen congestion control mechanism.

DCCP operates over IP (both IPv4 and IPv6) and supports features such as explicit congestion notification (ECN) and sequencing within a connection. It defines a network-level protocol state machine and a header format that includes fields for sequence numbers, connection management, and error reporting. The CCID framework allows multiple congestion control schemes to be used without changing the protocol core.

DCCP was standardized by the Internet Engineering Task Force in RFC 4340, published in 2006. While it provides an attractive model for congestion-controlled datagram transport, it has seen limited adoption in production networks, with relatively few mainstream applications or deployments.