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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>27.1.2.0.1 Centralized Multicast</TITLE><META NAME="description" CONTENT="27.1.2.0.1 Centralized Multicast"><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="node320.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node320.html"><LINK REL="previous" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html"><LINK REL="up" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html"><LINK REL="next" HREF="node320.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node320.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html6234" HREF="node320.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node320.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html6228" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html6222" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html6230" 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="tex2html6232" 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="tex2html6235" HREF="node320.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node320.html">27.1.2.0.2 Dense Mode</A><B> Up:</B> <A NAME="tex2html6229" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html">27.1.2 Protocol Specific configuration</A><B> Previous:</B> <A NAME="tex2html6223" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html">27.1.2 Protocol Specific configuration</A>   <B> <A NAME="tex2html6231" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html6233" 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="SECTION05212010000000000000">27.1.2.0.1 Centralized Multicast</A></H4>The centralized multicast is a sparse mode implementation of multicastsimilar to PIM-SM [<A HREF="node589.html#Deer94a:Architecture" tppabs="http://www.isi.edu/nsnam/ns/doc/node589.html#Deer94a:Architecture">11</A>].A Rendezvous Point (RP) rooted shared tree is builtfor a multicast group. The actual sending of prune, join messagesetc. to set up state at the nodes is not simulated. A centralizedcomputation agent is used to compute the forwarding trees and set upmulticast forwarding state, S, G at the relevant nodes as newreceivers join a group. Data packets from the senders to a group areunicast to the RP. Note that data packets from the senders areunicast to the RP even if there are no receivers for the group.<P>The method of enabling centralised multicast routing in a simulation is:<PRE> set mproto CtrMcast # set multicast protocol; set mrthandle [$ns mrtproto $mproto]</PRE>The command procedure []mrtprotoreturns a handle to the multicast protocol object.This handle can be used to control the RP and the boot-strap-router (BSR),switch tree-types for a particular group,from shared trees to source specific trees, andrecompute multicast routes.<PRE> $mrthandle set_c_rp $node0 $node1 # set the RPs; $mrthandle set_c_bsr $node0:0 $node1:1 # set the BSR, specified as list of node:priority; $mrthandle get_c_rp $node0 $group # get the current RP ???; $mrthandle get_c_bsr $node0 # get the current BSR; $mrthandle switch-treetype $group # to source specific or shared tree; $mrthandle compute-mroutes # recompute routes. usually invoked automatically as needed;</PRE><P>Note that whenever network dynamics occur or unicast routing changes,[]compute-mroutes could be invoked to recompute the multicast routes.The instantaneous re-computation feature of centralised algorithmsmay result in causality violations during the transientperiods.<P><HR><!--Navigation Panel--><A NAME="tex2html6234" HREF="node320.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node320.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html6228" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html6222" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html6230" 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="tex2html6232" 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="tex2html6235" HREF="node320.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node320.html">27.1.2.0.2 Dense Mode</A><B> Up:</B> <A NAME="tex2html6229" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html">27.1.2 Protocol Specific configuration</A><B> Previous:</B> <A NAME="tex2html6223" HREF="node318.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node318.html">27.1.2 Protocol Specific configuration</A>   <B> <A NAME="tex2html6231" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html6233" 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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