Datagram Congestion Control Protocol (DCCP)

Eddie Kohler, Mark Handley, Sally Floyd, Jitendra Padhye
ICIR

Formerly known as Datagram Control Protocol (DCP)

Current RFCs and Internet-Drafts | IETF reviews | Other documents | Mailing list | Prototype implementations | WG and BOF info, slides from talks | Document history

Current RFCs and Internet-Drafts

• Problem Statement for DCCP
  Sally Floyd, Mark Handley, and Eddie Kohler
  [Aug 2005] draft-ietf-dccp-problem-03.txt (TXT) // draft-ietf-dccp-problem-03.ps (PS)

• Datagram Congestion Control Protocol (DCCP)
  Eddie Kohler, Mark Handley, and Sally Floyd
  [Dec 2005] draft-ietf-dccp-spec-13.txt (TXT) // draft-ietf-dccp-spec-13.ps (PS)

  Changes from dccp-11 to dccp-13: Side-by-side HTML / text diff / substantive diffs with explanation
  Changes from dccp-12 to dccp-13: Side-by-side HTML / text diff
  Changes from dccp-11 to dccp-12: Side-by-side HTML / text diff / substantive diffs with explanation
  Changes from dccp-10 to dccp-11: text diff
  Changes from dccp-09 to dccp-10: Side-by-side HTML / text diff / substantive diffs with explanation
  

• Profile for DCCP Congestion Control ID 2: TCP-like Congestion Control
  Sally Floyd and Eddie Kohler
  [Mar 2005] draft-ietf-dccp-ccid2-10.txt (TXT) // draft-ietf-dccp-ccid2-10.ps (PS)

  Changes from dccp-08 to dccp-09: Side-by-side HTML / text diff / substantive diffs with explanation
  Changes from dccp-09 to dccp-10: text diff

• Profile for DCCP Congestion Control ID 3: TFRC Congestion Control
  Sally Floyd, Eddie Kohler, and Jitendra Padhye
  [Mar 2005] draft-ietf-dccp-ccid3-11.txt (TXT) // draft-ietf-dccp-ccid3-11.ps (PS)

  Changes from dccp-09 to dccp-10: Side-by-side HTML / text diff / substantive diffs with explanation
  Changes from dccp-10 to dccp-11: text diff

• DCCP CCID 3-Thin
  Eddie Kohler
  [Jul 2004] draft-ietf-dccp-ccid3-thin-01.txt (TXT) // draft-ietf-dccp-ccid3-thin-01.ps (PS)

• DCCP Mobility
  Eddie Kohler
  [Jan 2006] draft-kohler-dccp-mobility-01.txt (TXT) // draft-kohler-dccp-mobility-01.ps (PS)

• TCP Friendly Rate Control (TFRC) for Voice: VoIP Variant
  Sally Floyd and Eddie Kohler
  [Jul 2005] draft-ietf-dccp-tfrc-voip-02.txt (TXT) // draft-ietf-dccp-tfrc-voip-02.ps (PS)

• Faster Restart for TCP Friendly Rate Control (TFRC)
  Eddie Kohler and Sally Floyd
  [Jul 2005] draft-ietf-dccp-tfrc-faster-restart-00.txt (TXT)

• Strategies for Streaming Media Applications Using TCP-Friendly Rate Control
  Tom Phelan
  [Jul 2005] draft-ietf-dccp-tfrc-media-00.txt (TXT)

• Datagram Congestion Control Protocol (DCCP) User Guide
  Tom Phelan
  [Jul 2004] draft-ietf-dccp-user-guide-02.txt (TXT)

Document History

IETF Reviews

• Expert reviews
  Greg Minshall [Jun 2003]: main spec review, CCID 2 review; authors' response; further messages: 1
  Eric Rescorla [Jun 2003]: main spec review; authors' response; further messages: 1, 2

• Design review [Jul 2003]
  Slides; Minutes
  Magnus Westerlund: main spec review; CCID 2; CCID 3
  Rob Austein: review
  Steve Bellovin: message 1, message 2, message 3

Other Documents

• LTSA Model
  Mark Handley

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

• DCCP Overview
  Eddie Kohler and Sally Floyd
  PS // PDF

  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. ...

• A Congestion-Controlled Unreliable Datagram API
  Junwen Lai and Eddie Kohler

  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.

• Designing DCCP: Congestion Control Without Reliability (technical report)
  Eddie Kohler, Mark Handley, and Sally Floyd
  [PDF]

  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.

DCCP Mailing List

This IETF mailing list is the right place to discuss DCCP.

• dccp@ietf.org
• Mailing list information page

Prototype implementations

A number of people are working on prototype DCCP implementations. Write the mailing list if you are, too, and would like us to add a link to your Web page.

• Kernel DCCP for Linux 2.6, by Arnaldo Carvalho de Melo, Ian McDonald, et al.
  • CVS viewer
  • Status blog
  • Current status: Will be part of the official 2.6.14 release!
  • Messages sent to the dccp mailing list: 1, 2
• Kernel DCCP for Linux 2.4, based on Luleå's and Patrick McManus's implementations, from Ian McDonald, Richard Nelson, et al. at University of Waikato, New Zealand
  • Announcement message
• Kernel DCCP for Linux 2.4.20, created at ICIR by Junwen Lai and Arun Venkataramani with Eddie Kohler. NOT ACTIVELY MAINTAINED. The purpose of this implementation was to see how hard it was to implement the spec; the experience resulted in many changes to the spec, some important. (Particular changes included a simplified feature negotiation mechanism and the appendix on implementing Ack Vector.) Not all spec changes made it into this implementation.
  • Code: linux-2.4.20-dccp-modifications.tgz -- Extract this tarball from within the linux-2.4.20 directory.
• University of Luleå, Sweden implementation: kernel DCCP for FreeBSD, by Joacim Häggmark, Nils-Erik Mattsson, and Magnus Erixzon
  • Announcement message to the dccp mailing list
  • Current status
• Patrick McManus's Linux 2.4.18 kernel DCCP (NOT ACTIVELY MAINTAINED)
• A user-level DCCP from Berkeley, by Timothy Sohn, Eiman Zolfaghari, Alkis Evlogimenos, Khian Hao Lim, and Kevin Lai (OLD, NOT ACTIVELY MAINTAINED)
• Updated version of the Berkeley user-level DCCP, from Pedro Vale Estrela

DCCP WGs and BOFs

DCCP Working Group

63rd IETF (Paris, Aug 2005)

• Slides

62nd IETF (Minneapolis, Mar 2005)

• Minutes

61st IETF (Washington, DC, Nov 2004)

• Minutes
• Slides

60th IETF (San Diego, Aug 2004)

• Minutes
• Slides

59th IETF (Seoul, Feb 2004)

• Minutes
• Slides

58th IETF (Minneapolis, Nov 2003)

• Minutes
• Slides

57th IETF (Vienna, Jul 2003)

• Minutes
• Slides
• Eddie's overview talk at apparea: Datagram Congestion Control Protocol (DCCP): Overview [for Apparea]
• Aaron's intro talk at dccp: Datagram Congestion Control (dccp)
• Eddie's spec walkthrough talk at dccp: Datagram Congestion Control Protocol (DCCP) Spec Walkthrough
• Eddie's reviewer comments summary talk at dccp: DCCP Written Reviewer Comments
• Summary of reviewer comments at dccp: Comments heard today
• Aaron's closing slides at dccp: Next Steps

56th IETF (San Francisco, Mar 2003)

• Minutes
• Slides

55th IETF (Atlanta, Nov 2002)

• Minutes, including slides from presentations by Aaron Falk, Mark Handley, and Damon Lamphear

54th IETF (Yokohama, Jul 2002)

DCCP was discussed at a WG chaired by Aaron Falk at the Yokohama IETF (Monday, 15 July 2002, 1-3pm).

• Minutes
• Aaron's WG intro talk: Datagram Congestion Control Protocol dccp (PDF)
• Sally's WG talk: Problem Statement for DCP (PDF)
• Eddie's WG talk: DCCP changes, open issues, & implementations (PDF)
• Notes from the meeting

52nd IETF (Salt Lake City, Dec 2001)

DCCP was discussed at a BOF chaired by Aaron Falk at the Salt Lake City IETF (Tuesday, 11 December 2001, 5-6pm).

• Draft BOF agenda
• Mark's BOF talk: Motivation and Requirements for Datagram Control Protocol (PDF)
• Eddie's BOF talk: Datagram Control Protocol Overview (PDF)
• Notes from the meeting

51st IETF (London, Aug 2001)

• Discussion record

Old Internet-Drafts

Here are copies of previous DCCP Internet-Drafts, listed by draft in reverse chronological order.

• Datagram Control Protocol (DCP) / Datagram Congestion Control Protocol (DCCP)
  • kohler-00 [Jul 2001] TXT, PS
  • kohler-01 [Nov 2001] TXT, PS
  • kohler-02 [Mar 2002] TXT, PS
  • kohler-03 [May 2002] TXT, PS
    Changed name of protocol; renamed options; new state diagram; new Loss Window and Connection Nonce options/features address sequence number validity; Slow Receiver option; DCCP checksum includes a pseudoheader; Move packet format changed; added explanation of acks-of-acks.
  • kohler-04 [Jun 2002] TXT, PS
    Minor changes in CCID 3 discussion.
  • dccp-00 [Oct 2002] TXT, PS
    Clarify discussion on TCP friendliness, specify DCCP-Reset Reasons, replace Identify Yourself and Connection Proof with Challenge and Challenge Response, replace Buffer Closed Drops with Buffer Closed, allow use of Data Discarded on packets other than DCCP-Response, add discussion on Ack Vector state constraints, wording, acknowledgements.
  • dccp-01 [Mar 2003] TXT, PS
    Add Identification mechanism, replacing old Challenge mechanism; Identification is much less vulnerable to attack. Add discussion of DCCP and RTP. Clarify when packets are "received" for purposes of acknowledgement, partial checksums, and what ECN-incapable endpoints should use for the ECN nonce. Support Data Discarded on more packets. Mention wrapped sequence numbers for future work. Wording.
  • dccp-02 [May 2003] TXT, PS
    Change when packets are "received" for purposes of acknowledgement, due to ECN Nonce verification problems. (New definition is much better.) Replace Data Discarded, Receive Buffer Drops, and Buffer Closed with new Data Dropped option. Clarify timeouts and retransmissions. Change Identification option: only the Sequence Number is included in the MD5 Regime's hash. Add Payload Checksum and Elapsed Time options. Add Middlebox Considerations and Design Motivation sections. The 4-bit Reserved field in the DCCP generic header is available for use by CCIDs. Other changes.
  • dccp-03 [May 2003] TXT, PS
    (Minor revision) Include Acknowledgement Number in Identification options, and force it to be valid. Bad DCCP-Moves are ignored, not reset, to avoid leaking information to attackers.
  • dccp-04 [Jun 2003] TXT, PS
    Address some reviewer comments, including: Specify how the Loss Window is arranged. Ignored can contain multiple option data bytes. Refine the Ack Vector Consistency tables. CC mechanisms must treat Data Dropped like ECN Marked unless otherwise specified. Adjust MTU discovery.
  • dccp-05 [Oct 2003] TXT, PS
    New feature negotiation options, new resync mechanism, PAWS (48-bit sequence number option), DCCP-Move uses a Mobility ID, many other changes.
  • dccp-06 [Feb 2004] TXT, PS
  • dccp-07 [Jul 2004] TXT, PS
  • dccp-08 [Oct 2004] TXT, PS (HTML diff, changebars)
  • dccp-09 [Nov 2004] TXT, PS (HTML diff, changebars)
  • dccp-10 [Mar 2005] TXT, PS (HTML diff, text diff, text diff w/explanation)
  • dccp-11 [Mar 2005] TXT, PS (text diff)
  • dccp-12 [Nov 2005] TXT, PS (HTML diff, text diff, text diff w/explanation)

• Profile for DCP Congestion Control ID 0: Single-Window Congestion Control
  kohler-00 [Jul 2001] TXT, PS
  kohler-01 [Nov 2001] TXT, PS

• Profile for DCCP Congestion Control ID 2: TCP-like Congestion Control
  
  • floyd-00 [Jul 2001] TXT, PS
  • floyd-01 [Nov 2001] TXT, PS
  • floyd-02 [Mar 2002] TXT, PS
  • floyd-03 [May 2002] TXT, PS
  • dccp-00 [Oct 2002] TXT, PS
    Clarify discussion on when to acknowledge an acknowledgement.
  • dccp-01 [Mar 2003] TXT, PS
    Clarify ECN nonces, piggybacked acknowledgements, and the Acknowledgement Number. Wording.
  • dccp-02 [May 2003] TXT, PS
    Refer explicitly to SACK-based TCP, include more detail on sender-side congestion control, use appropriate "byte" counting, add Security and IANA considerations, small wording updates.
  • dccp-03 [Jun 2003] TXT, PS
    Address some reviewer comments: Add section on applicability. Change default Ack Ratio to two. Add paragraph about packet sizes.
  • dccp-04 [Oct 2003] TXT, PS
    Disallow direct tracking of TCP.
  • dccp-05 [Feb 2004] TXT, PS
  • dccp-06 [Jul 2004] TXT, PS
  • dccp-07 [Oct 2004] TXT, PS
  • dccp-08 [Nov 2004] TXT, PS (HTML diff, changebars)
  • dccp-09 [Mar 2005] TXT, PS (HTML diff, text diff, text diff)
  
  
• Profile for DCCP Congestion Control ID 3: TFRC Congestion Control
  
  • padhye-00 [Jul 2001] TXT, PS
  • padhye-01 [Nov 2001] TXT, PS
  • padhye-02 [Mar 2002] TXT, PS
  • padhye-03 [May 2002] TXT, PS
  • padhye-04 [Jun 2002] TXT, PS
    Minor corrections, and the addition of Section 8.2 on "Sending Feedback Packets".
  • dccp-00 [Oct 2002] TXT, PS
    Make option numbers consistent throughout the draft.
  • dccp-01 [Mar 2003] TXT, PS
    The ECN Nonce option is now called Loss Intervals, and reliably transmits information about the last eight loss intervals. This lets the sender calculate the loss event rate if desired. Added section on "The Use of Ack Vectors". Clarify ECN Nonce use. Other updates and wording.
  • dccp-02 [May 2003] TXT, PS
    Store Window Counter in the DCCP header's CCval field. Add Use Loss Intervals and Use Loss Event Rate features. Move Elapsed Time option to main DCCP specification, and change its units. Window counter updates; new sections; wording.
  • dccp-03 [Jun 2003] TXT, PS
    Address some reviewer comments: Add section on applicability. Add paragraph about packet sizes.
  • dccp-04 [Oct 2003] TXT, PS
    Change initial sending rate, adjust Loss Intervals option definition, improve readability.
  • dccp-05 [Feb 2004] TXT, PS
  • dccp-06 [Jul 2004] TXT, PS
  • dccp-07 [Oct 2004] TXT, PS
  • dccp-08 [Nov 2004] TXT, PS
  • dccp-09 [Nov 2004] TXT, PS (HTML diff, changebars)
  • dccp-10 [Mar 2005] TXT, PS (HTML diff, text diff, text diff)
  
  
• DCCP CCID 3-Thin
  
  • dccp-00 [Oct 2003] TXT, PS
  
  
• Problem Statement for DCCP
  
  • floyd-00b [Feb 2002] TXT, PS
  • floyd-01 [Aug 2002] TXT, PS
  • dccp-00 [Oct 2002] TXT, PS
  • dccp-01 [Jun 2005] TXT, PS
  • dccp-02 [Aug 2005] TXT, PS
  
  
• TCP Friendly Rate Control (TFRC) for Voice: VoIP Variant
  
  • dccp-00 [Dec 2004] TXT (includes Faster Restart)
  • dccp-01 [Mar 2005] TXT (includes Faster Restart)
  
  
• Datagram Congestion Control Protocol Mobility and Multihoming
  
  • kohler-00 [Jul 2004] TXT, PS