/share/man/man4/cc_htcp.4
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- .\" Copyright (c) 2008 Lawrence Stewart <lstewart@FreeBSD.org>
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- .Dd September 15, 2011
- .Dt CC_HTCP 4
- .Os
- .Sh NAME
- .Nm cc_htcp
- .Nd H-TCP Congestion Control Algorithm
- .Sh DESCRIPTION
- The H-TCP congestion control algorithm was designed to provide increased
- throughput in fast and long-distance networks.
- It attempts to maintain fairness when competing with legacy NewReno TCP in lower
- speed scenarios where NewReno is able to operate adequately.
- .Pp
- The congestion window is increased as a function of the time elapsed since the
- last congestion event.
- The window increase algorithm operates like NewReno for the first second after a
- congestion event, and then switches to a high-speed mode based on a quadratic
- increase function.
- .Pp
- The implementation was done in a clean-room fashion, and is based on the
- Internet Draft and other documents referenced in the
- .Sx SEE ALSO
- section below.
- .Sh MIB Variables
- The algorithm exposes the following tunable variables in the
- .Va net.inet.tcp.cc.htcp
- branch of the
- .Xr sysctl 3
- MIB:
- .Bl -tag -width ".Va adaptive_backoff"
- .It Va adaptive_backoff
- Controls use of the adaptive backoff algorithm, which is designed to keep
- network queues non-empty during congestion recovery episodes.
- Default is 0 (disabled).
- .It Va rtt_scaling
- Controls use of the RTT scaling algorithm, which is designed to make congestion
- window increase during congestion avoidance mode invariant with respect to RTT.
- Default is 0 (disabled).
- .El
- .Sh SEE ALSO
- .Xr cc_chd 4 ,
- .Xr cc_cubic 4 ,
- .Xr cc_hd 4 ,
- .Xr cc_newreno 4 ,
- .Xr cc_vegas 4 ,
- .Xr mod_cc 4 ,
- .Xr tcp 4 ,
- .Xr mod_cc 9
- .Rs
- .%A "D. Leith"
- .%A "R. Shorten"
- .%T "H-TCP: TCP Congestion Control for High Bandwidth-Delay Product Paths"
- .%U "http://tools.ietf.org/id/draft-leith-tcp-htcp-06.txt"
- .Re
- .Rs
- .%A "D. Leith"
- .%A "R. Shorten"
- .%A "T. Yee"
- .%T "H-TCP: A framework for congestion control in high-speed and long-distance networks"
- .%B "Proc. PFLDnet"
- .%D "2005"
- .Re
- .Rs
- .%A "G. Armitage"
- .%A "L. Stewart"
- .%A "M. Welzl"
- .%A "J. Healy"
- .%T "An independent H-TCP implementation under FreeBSD 7.0: description and observed behaviour"
- .%J "SIGCOMM Comput. Commun. Rev."
- .%V "38"
- .%N "3"
- .%D "July 2008"
- .%P "27-38"
- .Re
- .Sh ACKNOWLEDGEMENTS
- Development and testing of this software were made possible in part by grants
- from the FreeBSD Foundation and Cisco University Research Program Fund at
- Community Foundation Silicon Valley.
- .Sh HISTORY
- The
- .Nm
- congestion control module first appeared in
- .Fx 9.0 .
- .Pp
- The module was first released in 2007 by James Healy and Lawrence Stewart whilst
- working on the NewTCP research project at Swinburne University of Technology's
- Centre for Advanced Internet Architectures, Melbourne, Australia, which was made
- possible in part by a grant from the Cisco University Research Program Fund at
- Community Foundation Silicon Valley.
- More details are available at:
- .Pp
- http://caia.swin.edu.au/urp/newtcp/
- .Sh AUTHORS
- .An -nosplit
- The
- .Nm
- congestion control module was written by
- .An James Healy Aq jimmy@deefa.com
- and
- .An Lawrence Stewart Aq lstewart@FreeBSD.org .
- .Pp
- This manual page was written by
- .An Lawrence Stewart Aq lstewart@FreeBSD.org
- and
- .An David Hayes Aq david.hayes@ieee.org .