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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>39.1 Introduction</TITLE><META NAME="description" CONTENT="39.1 Introduction"><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="node542.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node542.html"><LINK REL="previous" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html"><LINK REL="up" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html"><LINK REL="next" HREF="node542.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node542.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html9728" HREF="node542.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node542.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html9722" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html9716" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html9724" 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="tex2html9726" 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="tex2html9729" HREF="node542.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node542.html">39.2 Real-Time Scheduler</A><B> Up:</B> <A NAME="tex2html9723" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html">39. Emulation</A><B> Previous:</B> <A NAME="tex2html9717" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html">39. Emulation</A>   <B> <A NAME="tex2html9725" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html9727" 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="SECTION09110000000000000000">39.1 Introduction</A></H1><P>The emulation facility can be subdivided intotwo modes:<OL><LI><I>opaque mode</I> - live data treated as opaque data packets</LI><LI><I>protocol mode</I> - live data may be interpreted/generated by simulator</LI></OL>In opaque mode, the simulatortreats network data as uninterpreted packets.In particular, real-world protocol fieldsare not directly manipulated by the simulator.In opaque mode, live data packets may be dropped, delayed, re-ordered, orduplicated, but because no protocol processing is performed,protocol-specific traffic manipulation scenarios (e.g. ``drop the TCP segmentcontaining a retransmission of sequence number 23045'') may not be performed.In protocol mode, the simulator is able to interpret and/or generatelive network traffic containing arbitrary field assignments.<B>To date (Mar 1998), only Opaque Mode is currently implemented</B>.<P>The interface between the simulator and live network is provided bya collection of objects including <EM>tap agents</EM> and <EM>network objects</EM>.Tap agents embed live network data into simulated packets andvice-versa.Network objects are installed in tap agents and provide an entrypointfor the sending and receipt of live data.Both objects are described in the following sections.<P>When using the emulation mode, a special version of the systemscheduler is used: the <TT>RealTime</TT> scheduler.This scheduler uses the same underlying structure as thestandard calendar-queue based scheduler, but ties the execution ofevents to real-time.It is described below.<P><HR><!--Navigation Panel--><A NAME="tex2html9728" HREF="node542.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node542.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html9722" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html9716" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html9724" 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="tex2html9726" 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="tex2html9729" HREF="node542.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node542.html">39.2 Real-Time Scheduler</A><B> Up:</B> <A NAME="tex2html9723" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html">39. Emulation</A><B> Previous:</B> <A NAME="tex2html9717" HREF="node540.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node540.html">39. Emulation</A>   <B> <A NAME="tex2html9725" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html9727" 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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