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<html><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><!--Converted with jLaTeX2HTML 2002 (1.62) JA patch-1.4patched version by: Kenshi Muto, Debian Project.LaTeX2HTML 2002 (1.62),original version by: Nikos Drakos, CBLU, University of Leeds* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan* with significant contributions from: Jens Lippmann, Marek Rouchal, Martin Wilck and others --><HTML><HEAD><TITLE>33.5.0.0.3 Mechanisms for Statistics</TITLE><META NAME="description" CONTENT="33.5.0.0.3 Mechanisms for Statistics"><META NAME="keywords" CONTENT="everything"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"><META NAME="Generator" CONTENT="jLaTeX2HTML v2002 JA patch-1.4"><META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css"><LINK REL="STYLESHEET" HREF="everything.css" tppabs="http://www.isi.edu/nsnam/ns/doc/everything.css"><LINK REL="previous" HREF="node448.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node448.html"><LINK REL="up" HREF="node446.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node446.html"><LINK REL="next" HREF="node450.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node450.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html8287" HREF="node450.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node450.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html8281" HREF="node446.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node446.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html8277" HREF="node448.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node448.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html8283" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html"><IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="file:/usr/share/latex2html/icons/contents.png"></A> <A NAME="tex2html8285" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html"><IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="file:/usr/share/latex2html/icons/index.png"></A> <BR><B> Next:</B> <A NAME="tex2html8288" HREF="node450.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node450.html">33.6 Session Objects</A><B> Up:</B> <A NAME="tex2html8282" HREF="node446.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node446.html">33.5 Loss Recovery Objects</A><B> Previous:</B> <A NAME="tex2html8278" HREF="node448.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node448.html">33.5.0.0.2 Repair Mechanisms</A>   <B> <A NAME="tex2html8284" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html8286" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <BR><BR><!--End of Navigation Panel--><H4><A NAME="SECTION06450030000000000000">33.5.0.0.3 Mechanisms for Statistics</A></H4>The agent, in concert with the request and repair objects, collect statistics about their response to data loss [<A HREF="node589.html#Floy95:Reliable" tppabs="http://www.isi.edu/nsnam/ns/doc/node589.html#Floy95:Reliable">13</A>].Each call to the agent []request procedure marks a new period.At the start of a new period,[]mark-period../ns-2/srm.tclAgent/SRM::mark-periodcomputes the moving average of the number of duplicates in the last period.Whenever the agent receives a first round request from another agent,and it had sent a request in that round, then it considers the requestas a duplicate request, and increments the appropriate counters.A request object does not consider duplicate requests if it did notitself send a request in the first round. If the agent has a repair object pending, then it does not considerthe arrival of duplicate requests for that packet.The object methods[]SRM/request::dup-request?../ns-2/srm.tclSRM/request::dup-request? and[]SRM/repair::dup-request?../ns-2/srm.tclSRM/repair::dup-request? encode these policies, and return 0 or 1 as required.<P>A request object also computes the elapsed time between when the loss is detected to when it receives the first request.The agent computes a moving average of this elapsed time.The object computes the elapsed time (or delay) when itcancels../ns-2/srm.tclSRM/request::cancelits scheduled event for the first round.The object invokesAgent/SRM::update-ave../ns-2/srm.tclAgent/SRM::update-aveto compute the moving average of the delay.<P>The agent keeps similar statistics of the duplicate repairs,and the repair delay.<P>The agent stores the number of rounds taken for one loss recovery,to ensure that subsequent loss recovery phases for that packetthat are not definitely not due to data lossdo not account for these statistics.The agent stores the number of routes taken for a phase inthe array <TT>old_</TT>.When a new loss recovery object is instantiated,the object will use the agent's instance procedure[]round?../ns-2/srm.tclAgent/SRM::round?to determine the number of rounds in a previous loss recovery phasefor that packet.<P><HR><!--Navigation Panel--><A NAME="tex2html8287" HREF="node450.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node450.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html8281" HREF="node446.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node446.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html8277" HREF="node448.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node448.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html8283" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html"><IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="file:/usr/share/latex2html/icons/contents.png"></A> <A NAME="tex2html8285" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html"><IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="file:/usr/share/latex2html/icons/index.png"></A> <BR><B> Next:</B> <A NAME="tex2html8288" HREF="node450.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node450.html">33.6 Session Objects</A><B> Up:</B> <A NAME="tex2html8282" HREF="node446.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node446.html">33.5 Loss Recovery Objects</A><B> Previous:</B> <A NAME="tex2html8278" HREF="node448.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node448.html">33.5.0.0.2 Repair Mechanisms</A>   <B> <A NAME="tex2html8284" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html8286" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <!--End of Navigation Panel--><ADDRESS>2003-09-23</ADDRESS></BODY></HTML>⌨️ 快捷键说明
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