Profile for Datagram Congestion Control Protocol (DCCP) Congestion ID 4: TCP-Friendly Rate Control for Small Packets (TFRC-SP)
RFC 5622

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Network Working Group                                           S. Floyd
Request for Comments: 5622                                          ICIR
Category: Experimental                                         E. Kohler
                                                                    UCLA
                                                             August 2009

        Profile for Datagram Congestion Control Protocol (DCCP)
 Congestion ID 4: TCP-Friendly Rate Control for Small Packets (TFRC-SP)

Abstract

   This document specifies a profile for Congestion Control Identifier
   4, the small-packet variant of TCP-Friendly Rate Control (TFRC), in
   the Datagram Congestion Control Protocol (DCCP).  CCID 4 is for
   experimental use, and uses TFRC-SP (RFC 4828), a variant of TFRC
   designed for applications that send small packets.  CCID 4 is
   considered experimental because TFRC-SP is itself experimental, and
   is not proposed for widespread deployment in the global Internet at
   this time.  The goal for TFRC-SP is to achieve roughly the same
   bandwidth in bits per second (bps) as a TCP flow using packets of up
   to 1500 bytes but experiencing the same level of congestion.  CCID 4
   is for use for senders that send small packets and would like a TCP-
   friendly sending rate, possibly with Explicit Congestion Notification
   (ECN), while minimizing abrupt rate changes.

Status of This Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

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Floyd & Kohler                Experimental                      [Page 1]
RFC 5622                Profile for DCCP CCID 4              August 2009

   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ....................................................3
   2. Conventions .....................................................4
   3. Usage ...........................................................4
      3.1. Relationship with TFRC and TFRC-SP .........................5
      3.2. Example Half-Connection ....................................5
   4. Connection Establishment ........................................6
   5. Congestion Control on Data Packets ..............................6
      5.1. Response to Idle and Application-Limited Periods ...........7
      5.2. Response to Data Dropped and Slow Receiver .................7
      5.3. Packet Sizes ...............................................7
   6. Acknowledgements ................................................8
      6.1. Loss Interval Definition ...................................8
      6.2. Congestion Control on Acknowledgements .....................8
      6.3. Acknowledgements of Acknowledgements .......................8
      6.4. Quiescence .................................................8
   7. Explicit Congestion Notification ................................8
   8. Options and Features ............................................9
      8.1. Window Counter Value ......................................10
      8.2. Elapsed Time Options ......................................10
      8.3. Receive Rate Option .......................................10
      8.4. Send Loss Event Rate Feature ..............................10
      8.5. Loss Event Rate Option ....................................11
      8.6. Loss Intervals Option .....................................11
      8.7. Dropped Packets Option ....................................11
           8.7.1. Example ............................................13
   9. Verifying Congestion Control Compliance with ECN ...............14
      9.1. Verifying the ECN Nonce Echo ..............................14
      9.2. Verifying the Reported Loss Intervals and Loss