Datagram Congestion Control Protocol (DCCP)

The Datagram Congestion Control Protocol (DCCP) is a transport protocol that provides bidirectional unicast connections of congestion-controlled unreliable datagrams. DCCP is suitable for applications that transfer fairly large amounts of data and that can benefit from control over the tradeoff between timeliness and reliability.

• History: for old drafts and differences between versions

• DCCP Working Group Information
• Mailing list: dccp@ietf.org
• Mailing list information page
• Meetings and reviews

• History: for old drafts and differences between versions

• Linux 2.6 DCCP Implementation Wiki
  • Linux 2.6.14 and later include a DCCP stack maintained by Arnaldo Cavalho de Melo, with contributions by Ian McDonald and others.
• tcpdump 3.9.4 and later includes DCCP support
• Preliminary FreeBSD implementation
• DCCP packet level test-suite.
• Other implementations

• Discovering Chatter and Incompleteness in the Datagram Congestion Control Protocol (PDF), by Somsak Vanit-Anunchai, Jonathan Billington, and Tul Kongprakaiwoot. Proc. FORTE 2005, LNCS 3731, Springer-Verlag, 2005.
  • Models DCCP using Coloured Petri Nets (CPNs), discovering several bugs. These bugs are fixed in the published RFC thanks to the authors.

• LTSA Model, by Mark Handley
  • This model, derived from an early version of draft-ietf-dccp-spec-05.txt, formalizes properties of the DCCP state machine. It can be used to check DCCP for properties like deadlock freedom.

• Designing DCCP: Congestion Control Without Reliability (PDF), by Eddie Kohler, Mark Handley, and Sally Floyd. Technical report.
  • Abstract: DCCP, the Datagram Congestion Control Protocol, is a new transport protocol in the TCP/UDP family that provides a congestion-controlled flow of unreliable datagrams. Delay-sensitive applications, such as streaming media and telephony, prefer timeliness to reliability. These applications have historically used UDP and implemented their own congestion control mechanisms---a difficult task---or no congestion control at all. DCCP will make it easy to deploy these applications without risking congestion collapse. It aims to add to a UDP-like foundation the minimum mechanisms necessary to support congestion control, such as possibly-reliable transmission of acknowledgement information. This minimal design should make DCCP suitable as a building block for more advanced application semantics, such as selective reliability. We introduce and motivate the protocol and discuss some of its design principles. Those principles particularly shed light on the ways TCP's reliable byte-stream semantics influence its implementation of congestion control.

• Efficiency and Late Data Choice in a User-Kernel Interface for Congestion-Controlled Datagrams (PDF), by Junwen Lai and Eddie Kohler. Proc. 12th Annual SPIE Conference on Multimedia Computing and Networking (MMCN '05), San Jose, CA, January 2005.
  • Describes a potential DCCP API based on a shared-memory packet ring. The API simultaneously achieves kernel-implemented congestion control, high throughput, and late data choice, where the app can change what's sent very late in the process. Shows that congestion-controlled DCCP API can improve the rate of "important" frames delivered, relative to non-congestion-controlled UDP, in some situations.
  • A one-page summary (PDF)

• DCCP Overview (PDF), by Eddie Kohler and Sally Floyd. Unpublished.
  • Intended as a quick overview for DCCP newcomers. Abstract: We provide a short overview of ... DCCP, which implements a congestion-controlled, unreliable flow of datagrams suitable for use by applications such as streaming media. ...