DCCP (Datagram Congestion Control Protocol) is a transport protocol that sits somewhere between TCP and UDP in terms of its features. It was designed to provide a way to handle congestion for applications that require a balance between the reliability of TCP and the simplicity of UDP.

Here are the main features and characteristics of DCCP:

  1. Connection-Oriented: Like TCP, DCCP is connection-oriented, meaning that it establishes a connection before data transfer begins and maintains that connection throughout the session.
  2. Unreliable Transport: Unlike TCP, DCCP does not guarantee the delivery of packets. It is designed for applications where timely delivery is more critical than the delivery of all packets. Examples might include streaming media, online games, and VoIP, where it’s more important to maintain a consistent flow than to ensure every packet arrives.
  3. Built-in Congestion Control: As the name suggests, one of the primary features of DCCP is its in-built congestion control mechanisms. DCCP aims to be friendly to the network, ensuring that applications don’t overwhelm the available bandwidth and cause congestion.
  4. Feature Negotiation: DCCP supports feature negotiation between endpoints. This means that the two ends of a DCCP connection can agree upon specific features to use during their session.
  5. Modular Congestion Control: DCCP supports different congestion control profiles, allowing it to be adapted for different applications and network conditions. For instance, there’s a TCP-like congestion control profile and another one that resembles TCP’s friendly rate control.
  6. Checksum Coverage: DCCP includes a mechanism that allows applications to choose whether the payload should be covered by the checksum. This can be useful for applications like streaming media, where minor errors in the payload might be acceptable.
  7. Acknowledgments: DCCP uses acknowledgments, but they’re different from TCP’s. DCCP acknowledgments are used mainly for congestion control and not for reliability.
  8. Short Packet Headers: DCCP has been designed to have shorter headers than TCP, which can be beneficial for applications where bandwidth or efficiency is a concern.

In summary, DCCP provides a middle ground between TCP and UDP. It offers some of the connection setup and congestion control features of TCP but without the guaranteed delivery. It’s designed for applications that can tolerate some packet loss but need congestion control to be friendly to the network and other traffic.