/share/man/man4/cc_htcp.4

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  1. .\"
  2. .\" Copyright (c) 2008 Lawrence Stewart <lstewart@FreeBSD.org>
  3. .\" Copyright (c) 2010-2011 The FreeBSD Foundation
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  6. .\" Portions of this documentation were written at the Centre for Advanced
  7. .\" Internet Architectures, Swinburne University of Technology, Melbourne,
  8. .\" Australia by David Hayes under sponsorship from the FreeBSD Foundation.
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  31. .\" $FreeBSD$
  32. .\"
  33. .Dd September 15, 2011
  34. .Dt CC_HTCP 4
  35. .Os
  36. .Sh NAME
  37. .Nm cc_htcp
  38. .Nd H-TCP Congestion Control Algorithm
  39. .Sh DESCRIPTION
  40. The H-TCP congestion control algorithm was designed to provide increased
  41. throughput in fast and long-distance networks.
  42. It attempts to maintain fairness when competing with legacy NewReno TCP in lower
  43. speed scenarios where NewReno is able to operate adequately.
  44. .Pp
  45. The congestion window is increased as a function of the time elapsed since the
  46. last congestion event.
  47. The window increase algorithm operates like NewReno for the first second after a
  48. congestion event, and then switches to a high-speed mode based on a quadratic
  49. increase function.
  50. .Pp
  51. The implementation was done in a clean-room fashion, and is based on the
  52. Internet Draft and other documents referenced in the
  53. .Sx SEE ALSO
  54. section below.
  55. .Sh MIB Variables
  56. The algorithm exposes the following tunable variables in the
  57. .Va net.inet.tcp.cc.htcp
  58. branch of the
  59. .Xr sysctl 3
  60. MIB:
  61. .Bl -tag -width ".Va adaptive_backoff"
  62. .It Va adaptive_backoff
  63. Controls use of the adaptive backoff algorithm, which is designed to keep
  64. network queues non-empty during congestion recovery episodes.
  65. Default is 0 (disabled).
  66. .It Va rtt_scaling
  67. Controls use of the RTT scaling algorithm, which is designed to make congestion
  68. window increase during congestion avoidance mode invariant with respect to RTT.
  69. Default is 0 (disabled).
  70. .El
  71. .Sh SEE ALSO
  72. .Xr cc_chd 4 ,
  73. .Xr cc_cubic 4 ,
  74. .Xr cc_hd 4 ,
  75. .Xr cc_newreno 4 ,
  76. .Xr cc_vegas 4 ,
  77. .Xr mod_cc 4 ,
  78. .Xr tcp 4 ,
  79. .Xr mod_cc 9
  80. .Rs
  81. .%A "D. Leith"
  82. .%A "R. Shorten"
  83. .%T "H-TCP: TCP Congestion Control for High Bandwidth-Delay Product Paths"
  84. .%U "http://tools.ietf.org/id/draft-leith-tcp-htcp-06.txt"
  85. .Re
  86. .Rs
  87. .%A "D. Leith"
  88. .%A "R. Shorten"
  89. .%A "T. Yee"
  90. .%T "H-TCP: A framework for congestion control in high-speed and long-distance networks"
  91. .%B "Proc. PFLDnet"
  92. .%D "2005"
  93. .Re
  94. .Rs
  95. .%A "G. Armitage"
  96. .%A "L. Stewart"
  97. .%A "M. Welzl"
  98. .%A "J. Healy"
  99. .%T "An independent H-TCP implementation under FreeBSD 7.0: description and observed behaviour"
  100. .%J "SIGCOMM Comput. Commun. Rev."
  101. .%V "38"
  102. .%N "3"
  103. .%D "July 2008"
  104. .%P "27-38"
  105. .Re
  106. .Sh ACKNOWLEDGEMENTS
  107. Development and testing of this software were made possible in part by grants
  108. from the FreeBSD Foundation and Cisco University Research Program Fund at
  109. Community Foundation Silicon Valley.
  110. .Sh HISTORY
  111. The
  112. .Nm
  113. congestion control module first appeared in
  114. .Fx 9.0 .
  115. .Pp
  116. The module was first released in 2007 by James Healy and Lawrence Stewart whilst
  117. working on the NewTCP research project at Swinburne University of Technology's
  118. Centre for Advanced Internet Architectures, Melbourne, Australia, which was made
  119. possible in part by a grant from the Cisco University Research Program Fund at
  120. Community Foundation Silicon Valley.
  121. More details are available at:
  122. .Pp
  123. http://caia.swin.edu.au/urp/newtcp/
  124. .Sh AUTHORS
  125. .An -nosplit
  126. The
  127. .Nm
  128. congestion control module was written by
  129. .An James Healy Aq jimmy@deefa.com
  130. and
  131. .An Lawrence Stewart Aq lstewart@FreeBSD.org .
  132. .Pp
  133. This manual page was written by
  134. .An Lawrence Stewart Aq lstewart@FreeBSD.org
  135. and
  136. .An David Hayes Aq david.hayes@ieee.org .