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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>29.1 Overview of Hierarchical Routing</TITLE><META NAME="description" CONTENT="29.1 Overview of Hierarchical Routing"><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="node356.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node356.html"><LINK REL="previous" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html"><LINK REL="up" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html"><LINK REL="next" HREF="node356.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node356.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html6773" HREF="node356.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node356.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html6767" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html6761" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html6769" 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="tex2html6771" 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="tex2html6774" HREF="node356.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node356.html">29.2 Usage of Hierarchical</A><B> Up:</B> <A NAME="tex2html6768" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html">29. Hierarchical Routing</A><B> Previous:</B> <A NAME="tex2html6762" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html">29. Hierarchical Routing</A>   <B> <A NAME="tex2html6770" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html6772" 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="SECTION05410000000000000000"></A><A NAME="sec:over-hier-rtg"></A><BR>29.1 Overview of Hierarchical Routing</H1><P>Hierarchical routing was mainly devised, among other things, to reducememory requirements of simulations over very large topologies. Atopology is broken down into several layers of hierarchy, thusdownsizing the routing table. The table size is reduced from <EM></EM>, for flat routing, to about <EM>log n</EM> for hierarchical routing. However some overhead costs results as number of hierarchy levels are increased. Optimum results were found for3 levels of hierarchy and the current ns implementation supports upto amaximum of 3 levels of hierarchical routing. <P>To be able to use hierarchical routing for the simulations, we need todefine the hierarchy of the topology as well as provide the nodes withhierarchical addressing. In flat routing, every node knows about everyother node in the topology, thus resulting in routing table size to theorder of . For hierarchical routing, each node knows only aboutthose nodes in its level. For all other destinations outside its levelit forwards the packets to the border router of its level. Thus therouting table size gets downsized to the order of about log n.<P><HR><!--Navigation Panel--><A NAME="tex2html6773" HREF="node356.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node356.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html6767" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html6761" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html6769" 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="tex2html6771" 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="tex2html6774" HREF="node356.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node356.html">29.2 Usage of Hierarchical</A><B> Up:</B> <A NAME="tex2html6768" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html">29. Hierarchical Routing</A><B> Previous:</B> <A NAME="tex2html6762" HREF="node354.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node354.html">29. Hierarchical Routing</A>   <B> <A NAME="tex2html6770" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html6772" 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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