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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>23.2 Library support and examples</TITLE><META NAME="description" CONTENT="23.2 Library support and examples"><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="next" HREF="node269.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node269.html"><LINK REL="previous" HREF="node266.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node266.html"><LINK REL="up" HREF="node265.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node265.html"><LINK REL="next" HREF="node269.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node269.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html5415" HREF="node269.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node269.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html5409" HREF="node265.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node265.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html5403" HREF="node267.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node267.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html5411" 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="tex2html5413" 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="tex2html5416" HREF="node269.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node269.html">23.3 The C++ Trace</A><B> Up:</B> <A NAME="tex2html5410" HREF="node265.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node265.html">23. Trace and Monitoring</A><B> Previous:</B> <A NAME="tex2html5404" HREF="node267.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node267.html">23.1.1 OTcl Helper Functions</A>   <B> <A NAME="tex2html5412" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html5414" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <BR><BR><!--End of Navigation Panel--><H1><A NAME="SECTION04320000000000000000"></A><A NAME="sec:libexam"></A><BR>23.2 Library support and examples</H1><P>The <TT>Simulator</TT> procedures described above require the <TT>trace</TT>and <TT>init-monitor</TT> methods associated with the OTcl <TT>Link</TT> class.Several subclasses of link are defined, the most common of whichis called <TT>SimpleLink</TT>. Thus, the <TT>trace</TT> and <TT>init-monitor</TT>methods are actually part of the <TT>SimpleLink</TT> class rather thanthe <TT>Link</TT> base class.The <TT>trace</TT> function is defined as follows (in <TT>ns-link.tcl</TT>):<PRE>## Build trace objects for this link and# update the object linkage#SimpleLink instproc trace { ns f } { $self instvar enqT_ deqT_ drpT_ queue_ link_ head_ fromNode_ toNode_ $self instvar drophead_ set enqT_ [$ns create-trace Enque $f $fromNode_ $toNode_] set deqT_ [$ns create-trace Deque $f $fromNode_ $toNode_] set drpT_ [$ns create-trace Drop $f $fromNode_ $toNode_] $drpT_ target [$drophead_ target] $drophead_ target $drpT_ $queue_ drop-target $drpT_ $deqT_ target [$queue_ target] $queue_ target $deqT_ if { [$head_ info class] == "networkinterface" } { $enqT_ target [$head_ target] $head_ target $enqT_ # puts "head is i/f" } else { $enqT_ target $head_ set head_ $enqT_ # puts "head is not i/f" }}</PRE>This function establishes <TT>Enque</TT>, <TT>Deque</TT>, and <TT>Drop</TT>traces in the simulator <TT>$ns</TT> and directs theiroutput to I/O handle <TT>$f</TT>.The function assumes a queue has been associated with the link.It operates by first creating three new trace objectsand inserting the <TT>Enque</TT> object before the queue, the<TT>Deque</TT> object after the queue, and the <TT>Drop</TT> objectbetween the queue and its previous drop target.Note that all trace output is directed to the same I/O handle.<P>This function performs one other additional tasks.It checks to see if a link contains a network interface,and if so, leaves it as the first object in the chain of objectsin the link, but otherwise inserts the <TT>Enque</TT> object asthe first one.<P>The following functions, <TT>init-monitor</TT> and<TT>attach-monitor</TT>, are used to create a set ofobjects used to monitor queue sizes of a queue associatedwith a link.They are defined as follows:<PRE> SimpleLink instproc attach-monitors { insnoop outsnoop dropsnoop qmon } { $self instvar queue_ head_ snoopIn_ snoopOut_ snoopDrop_ $self instvar drophead_ qMonitor_ set snoopIn_ $insnoop set snoopOut_ $outsnoop set snoopDrop_ $dropsnoop $snoopIn_ target $head_ set head_ $snoopIn_ $snoopOut_ target [$queue_ target] $queue_ target $snoopOut_ $snoopDrop_ target [$drophead_ target] $drophead_ target $snoopDrop_ $snoopIn_ set-monitor $qmon $snoopOut_ set-monitor $qmon $snoopDrop_ set-monitor $qmon set qMonitor_ $qmon } # # Insert objects that allow us to monitor the queue size # of this link. Return the name of the object that # can be queried to determine the average queue size. # SimpleLink instproc init-monitor { ns qtrace sampleInterval} { $self instvar qMonitor_ ns_ qtrace_ sampleInterval_ set ns_ $ns set qtrace_ $qtrace set sampleInterval_ $sampleInterval set qMonitor_ [new QueueMonitor] $self attach-monitors [new SnoopQueue/In] \bs [new SnoopQueue/Out] [new SnoopQueue/Drop] $qMonitor_ set bytesInt_ [new Integrator] $qMonitor_ set-bytes-integrator $bytesInt_ set pktsInt_ [new Integrator] $qMonitor_ set-pkts-integrator $pktsInt_ return $qMonitor_ }</PRE>These functions establish queue monitoring on the <TT>SimpleLink</TT> objectin the simulator <TT>ns</TT>.Queue monitoring is implemented by constructing three <TT>SnoopQueue</TT>objects and one <TT>QueueMonitor</TT> object.The <TT>SnoopQueue</TT> objects are linked in around a <TT>Queue</TT> in a waysimilar to <TT>Trace</TT> objects.The <TT>SnoopQueue/In(Out)</TT> object monitors packet arrivals(departures)and reports them to an associated <TT>QueueMonitor</TT> agent.In addition, a <TT>SnoopQueue/Out</TT> object is also used to accumulatepacket drop statistics to an associated <TT>QueueMonitor</TT> object.For <TT>init-monitor</TT> the same <TT>QueueMonitor</TT> object is usedin all cases.The C++ definitions of the <TT>SnoopQueue</TT> and <TT>QueueMonitor</TT>classes are described below.<P><HR><!--Navigation Panel--><A NAME="tex2html5415" HREF="node269.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node269.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html5409" HREF="node265.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node265.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html5403" HREF="node267.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node267.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html5411" 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="tex2html5413" 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="tex2html5416" HREF="node269.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node269.html">23.3 The C++ Trace</A><B> Up:</B> <A NAME="tex2html5410" HREF="node265.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node265.html">23. Trace and Monitoring</A><B> Previous:</B> <A NAME="tex2html5404" HREF="node267.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node267.html">23.1.1 OTcl Helper Functions</A>   <B> <A NAME="tex2html5412" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html5414" 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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