Equation-Based Congestion Control for Unicast Applications

The Key TFRC Documents:

RFC 3448: TCP Friendly Rate Control (TFRC): Protocol Specification.
Handley, M., Floyd, S., Pahdye, J., and Widmer, J.
RFC 3448, Proposed Standard, January 2003. The local copy: (postscript, text). Errata.
RFC 3448bis: TCP Friendly Rate Control (TFRC): Protocol Specification.
Floyd, S., Handley, M., Pahdye, J., and Widmer, J.
Internet draft draft-ietf-dccp-rfc3448bis-06.txt, April 2008.
Local copy: (text, PDF). This is a revision of RFC 3448. Working Group Last Call ended March 21, 2008.
RFC 4828: TCP Friendly Rate Control (TFRC): the Small-Packet (SP) Variant ,
Sally Floyd and Eddie Kohler.
RFC 4828, Experimental, April 2007.
Local copy: (postscript, text). Simulation scripts and supporting documents.
Faster Restart for TCP Friendly Rate Control (TFRC).
E. Kohler, S. Floyd, and A. Sathiaseelan,
Internet draft draft-ietf-dccp-tfrc-faster-restart-05.txt, November 2007.
Local copy: (text, postscript).
[FHPW00] Equation-Based Congestion Control for Unicast Applications (postscript, PDF).
Sally Floyd, Mark Handley, Jitendra Padhye, and Joerg Widmer.
August 2000. SIGCOMM 2000. Slides.
Simulation scripts for running the simulations in [FHPW00].
[FHPW00a] Equation-Based Congestion Control for Unicast Applications: the Extended Version.
Sally Floyd, Mark Handley, Jitendra Padhye, and Joerg Widmer.
International Computer Science Institute tech report TR-00-03, March 2000 (postscript, gzipped postscript, PDF).
Simulation scripts for running the simulations in [FHPW00a].

Related Work:

[FHP00] A Comparison of Equation-Based and AIMD Congestion Control.
Sally Floyd, Mark Handley, and Jitendra Padhye.
May 2000. Preliminary version. (postscript, gzipped postscript, PDF).
An independent, related paper is the following:
General AIMD Congestion Control, by Y. Richard Yang and Simon S. Lam.
Simulation scripts for running the simulations in [FHP00].
Dynamic Behavior of Slowly-Responsive Congestion Control Algorithms (postscript, PDF).
Deepak Bansal, Hari Balakrishnan, Sally Floyd, and Scott Shenker
SIGCOMM 2001. Simulation scripts. And a few missing files.
[P00] Jitendra Padhye, Towards a Comprehensive Congestion Control Framework for Continuous Media Flows in Best Effort Networks (gzipped postscript), Ph.D. Thesis, University of Massachusetts Amherst, March 3, 2000.
[W00] Joerg Widmer, Equation-Based Congestion Control (gzipped postscript), Diploma Thesis, February 2000.
Milan Vojnovic and Jean-Yves Le Boudec, On the Long-Run Behavior of Equation-Based Rate Control, ACM SIGCOMM 2002, also IEEE/ACM Transactions on Networking 2005.
"Our findings provide guidelines that help understand when an equation base control is indeed TCP-friendly in the long run, and in some cases, excessively so."
Injong Rhee and Lisong Xu, Limitations of Equation-based Congestion Control, SIGCOMM 2005, also IEEE/ACM Transactions on Networking 2007.
"There are several fundamental reasons why TFRC and TCP flows have different average sending rates. Earlier work shows that the convexity of the TCP friendly equation used in TFRC causes the sending rate difference. We report two additional reasons in this paper: (1) the convexity of 1/x where x is a loss event period and (2) different RTO estimations of TCP and TFRC."
Dejan Kostic, Adolfo Rodriguez, Jeannie Albrech, and Amin Vahdat, Bullet: High Bandwidth Data Dissemination Using an Overlay Mesh. Proceedings of the 19th ACM Symposium on Operating System Principles, October 2003.
"We use TFRC to transfer data both down the overlay tree and among peers."
M. Welzl, User-Centric Evaluation of TCP-friendly Congestion Control for Real-Time Video Transmission", Elektrotechnik und Informationstechnik, June 2005.
"Our basic goal was to find an answer to the question: Is a smooth rate generally better for interactive video applications?"...; our answer is yes."

TFRC for Ad Hoc Networks

Mingzhe Li, Choong-Soo Lee, Emmanuel Agu, Mark Claypool, and Robert Kinicki, Performance Enhancement of TFRC in Wireless Ad Hoc Networks, Distributed Multimedia Systems (DMS), September 2004.
"We propose an enhancement to TFRC, called RE TFRC, that uses measurements of the current round-trip time and a model of wireless delay to restrict TFRC bitrates from overloading the MAC layer."
Zhenghua Fu, Xiaoqiao Meng, and Songwu Lu, A Transport Protocol For Supporting Multimedia Streaming in Mobile Ad Hoc Networks, IEEE JSAC, December 2004.
"We devise two metrics to detect congestion, i.e., IDD (Inter Delay Difference) and STT (Short Term Throughput). This technique ... improves TFRC performance significantly in ad hoc networks."
Kai Chen and Klara Nahrstedt, Limitations of Equation-based Congestion Control in Mobile Ad Hoc Networks. Workshop on Wireless Ad Hoc Networking (WWAN), March 2004.
"Our study shows the limitations of applying TFRC to the MANET domain, and reveals some fundamental difficulties in doing so."

Implementations

TFRC is used in the DCCP protocol, in CCID-3. Implementations are listed on the DCCP web page.
The Net:DCCP web page describes TFRC as implemented in the DCCP protocol in Linux.
Experimental code from 2000.
End System Multicast has used TFRC, and experimented with TFRC on the Internet.

Other Papers on TCP-Friendly Congestion Control

The TFRC code in the NS simulator:

The TFRC (TCP-Friendly Rate Control) code is included in NS. The NS daily snapshot contains the most recent version of the ns code.
The parameter numPkts_ was added to Agent/TFRCSink on 16-Dec-2002, for robustness against reordered packets. The parameter numPkts_ gives the number of non-sequential data packets before a missing packet is counted as a loss; a loss is inferred after numPkts_ non-sequential data packets have been received, or if a non-sequential data packet is received more than a round-trip time after the last sequential data packet was received. The old behavior of TFRC is identical to that with numPkts_ set to 1. The default for numPkts_ was set to 3 on 12/17/02, introducing the bug reported in bug reports. The default was changed back to 1 on 10/28/03, and should stay there until the bug in the NS code is fixed. This means that the current version of the code is not robust against reordering, until the bug is fixed and numPkts_ can be set back to 3.
To run the validation tests:
"./test-all-friendly" in the directory ~ns/tcl/test.
"./test-all-quiescent" in the directory ~ns/tcl/test.

Bug reports:

Thanks to Roy Chabata for contributions to this page.
More information on equation-based congestion control is available from the TCP-friendly web page.

Last modified: January 2008.