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diff --git a/static/freebsd/man4/cc_dctcp.4 3.html b/static/freebsd/man4/cc_dctcp.4 3.html new file mode 100644 index 00000000..db66dbac --- /dev/null +++ b/static/freebsd/man4/cc_dctcp.4 3.html @@ -0,0 +1,113 @@ +<table class="head"> + <tr> + <td class="head-ltitle">CC_DCTCP(4)</td> + <td class="head-vol">Device Drivers Manual</td> + <td class="head-rtitle">CC_DCTCP(4)</td> + </tr> +</table> +<div class="manual-text"> +<section class="Sh"> +<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1> +<p class="Pp"><code class="Nm">cc_dctcp</code> — <span class="Nd">DCTCP + Congestion Control Algorithm</span></p> +</section> +<section class="Sh"> +<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1> +<p class="Pp">The DCTCP (data center TCP) congestion control algorithm aims to + maximise throughput and minimise latency in data center networks by + utilising the proportion of Explicit Congestion Notification (ECN) marks + received from capable hardware as a congestion signal.</p> +<p class="Pp">DCTCP uses fraction of ECN marked packets to update congestion + window. The window reduction ratio is always <= 1/2. Only when all of the + packets are marked, congestion window is halved.</p> +<p class="Pp">In order to keep the accuracy of the ECN marked fraction, a DCTCP + receiver mirrors back incoming (or missing) CE marks by setting (or + clearing) ECE marks. This feedback methodology is also adopted when the + receiver uses delayed ACK.</p> +<p class="Pp">The <span class="Ux">FreeBSD</span> DCTCP implementation includes + two minor modifications for the one-sided deployment. Considering the + situation that DCTCP is used as sender and classic ECN is used as receiver, + DCTCP sets the CWR flag as the reaction to the ECE flag. In addition, when + classic ECN is used as sender and DCTCP is used as receiver, DCTCP avoids to + mirror back ACKs only when the CWR flag is set in the incoming packet.</p> +<p class="Pp">The other specifications are based on the paper and the RFC + referenced in the <a class="Sx" href="#SEE_ALSO">SEE ALSO</a> section + below.</p> +</section> +<section class="Sh"> +<h1 class="Sh" id="MIB_Variables"><a class="permalink" href="#MIB_Variables">MIB + Variables</a></h1> +<p class="Pp">The algorithm exposes the following tunable variables in the + <var class="Va">net.inet.tcp.cc.dctcp</var> branch of the + <a class="Xr">sysctl(3)</a> MIB:</p> +<dl class="Bl-tag"> + <dt id="alpha"><var class="Va">alpha</var></dt> + <dd>The initial value to estimate the congestion on the link. The valid range + is from 0 to 1024, where 1024 reduces the congestion window to half, if a + CE is observed in the first window and <var class="Va">alpha</var> could + not yet adjust to the congestion level on that path. Default is 1024.</dd> + <dt id="shift_g"><var class="Va">shift_g</var></dt> + <dd>An estimation gain in the <var class="Va">alpha</var> calculation. This + influences the responsiveness when adjusting alpha to the most recent + observed window. Valid range from 0 to 10, the default is 4, resulting in + an effective gain of 1 / ( 2 ^ <var class="Va">shift_g</var> ), or + 1/16th.</dd> + <dt id="slowstart"><var class="Va">slowstart</var></dt> + <dd>A flag if the congestion window should be reduced by one half after slow + start. Valid settings 0 and 1, default 0.</dd> + <dt id="ect1"><var class="Va">ect1</var></dt> + <dd>Controls if a DCTCP session should use IP ECT(0) marking when sending out + segments (default), or ECT(1) marking making use of L4S infrastructure. + Changes to this setting will only affect new sessions, existing sessions + will retain their previous marking value.</dd> +</dl> +</section> +<section class="Sh"> +<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE + ALSO</a></h1> +<p class="Pp"><a class="Xr">cc_cdg(4)</a>, <a class="Xr">cc_chd(4)</a>, + <a class="Xr">cc_cubic(4)</a>, <a class="Xr">cc_hd(4)</a>, + <a class="Xr">cc_htcp(4)</a>, <a class="Xr">cc_newreno(4)</a>, + <a class="Xr">cc_vegas(4)</a>, <a class="Xr">mod_cc(4)</a>, + <a class="Xr">tcp(4)</a>, <a class="Xr">mod_cc(9)</a></p> +<p class="Pp"><cite class="Rs"><span class="RsA">Mohammad Alizadeh</span>, + <span class="RsA">Albert Greenberg</span>, <span class="RsA">David A. + Maltz</span>, <span class="RsA">Jitendra Padhye</span>, + <span class="RsA">Parveen Patel</span>, <span class="RsA">Balaji + Prabhakar</span>, <span class="RsA">Sudipta Sengupta</span>, and + <span class="RsA">Murari Sridharan</span>, <span class="RsT">Data Center TCP + (DCTCP)</span>, <i class="RsJ">ACM SIGCOMM 2010</i>, + <a class="RsU" href="http://research.microsoft.com/pubs/121386/dctcp-public.pdf">http://research.microsoft.com/pubs/121386/dctcp-public.pdf</a>, + <span class="RsP">63-74</span>, <span class="RsD">July + 2010</span>.</cite></p> +<p class="Pp"><cite class="Rs"><span class="RsA">Stephen Bensley</span>, + <span class="RsA">Dave Thaler</span>, <span class="RsA">Praveen + Balasubramanian</span>, <span class="RsA">Lars Eggert</span>, and + <span class="RsA">Glenn Judd</span>, <span class="RsT">Data Center TCP + (DCTCP): TCP Congestion Control for Data Centers</span>, + <a class="RsU" href="https://tools.ietf.org/html/rfc8257">https://tools.ietf.org/html/rfc8257</a>.</cite></p> +</section> +<section class="Sh"> +<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1> +<p class="Pp">The <code class="Nm">cc_dctcp</code> congestion control module + first appeared in <span class="Ux">FreeBSD 11.0</span>.</p> +<p class="Pp">The module was first released in 2014 by Midori Kato studying at + Keio University, Japan.</p> +</section> +<section class="Sh"> +<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1> +<p class="Pp">The <code class="Nm">cc_dctcp</code> congestion control module and + this manual page were written by <span class="An">Midori Kato</span> + <a class="Mt" href="mailto:katoon@sfc.wide.ad.jp">katoon@sfc.wide.ad.jp</a> + and <span class="An">Lars Eggert</span> + <a class="Mt" href="mailto:lars@netapp.com">lars@netapp.com</a> with help + and modifications from <span class="An">Hiren Panchasara</span> + <a class="Mt" href="mailto:hiren@FreeBSD.org">hiren@FreeBSD.org</a></p> +</section> +</div> +<table class="foot"> + <tr> + <td class="foot-date">November 8, 2022</td> + <td class="foot-os">FreeBSD 15.0</td> + </tr> +</table> |