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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>16.2.1 wired-cum-wireless scenarios</TITLE><META NAME="description" CONTENT="16.2.1 wired-cum-wireless scenarios"><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="node192.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node192.html"><LINK REL="previous" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html"><LINK REL="up" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html"><LINK REL="next" HREF="node192.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node192.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html4211" HREF="node192.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node192.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html4205" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html4199" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html4207" 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="tex2html4209" 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="tex2html4212" HREF="node192.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node192.html">16.2.2 MobileIP</A><B> Up:</B> <A NAME="tex2html4206" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html">16.2 Extensions made to</A><B> Previous:</B> <A NAME="tex2html4200" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html">16.2 Extensions made to</A>   <B> <A NAME="tex2html4208" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html4210" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <BR><BR><!--End of Navigation Panel--><H2><A NAME="SECTION031321000000000000000"></A><A NAME="sec:wired-cum-wireless"></A><BR>16.2.1 wired-cum-wireless scenarios</H2><P>The mobilenodes described so far mainly supports simulation ofmulti-hop ad-hoc networks or wireless LANs. But what if we need tosimulate a topology of multiple wireless LANs connected through wirednodes, or may need to run mobileIP on top of these wireless nodes? Theextensions made to the CMU wireless model allows us to do that. <P>The main problem facing the wired-cum-wireless scenario was the issueof routing. In ns, routing information is generated based on theconnectivity of the topology, i.e how nodes are connected to oneanother through <TT>Links</TT>. Mobilenodes on the other hand have noconcept of links. They route packets among themselves, within thewireless topology, using their routing protocol. so how would packetsbe exchanged between these two types of nodes? <P>So a node called <TT>BaseStationNode</TT> is created which plays therole of a gateway for the wired and wireless domains. The<TT>BaseStationNode</TT> is essentially a hybrid between a Hierarchicalnode<A NAME="tex2html27" HREF="footnode.html#foot7070" tppabs="http://www.isi.edu/nsnam/ns/doc/footnode.html#foot7070"><SUP>16.1</SUP></A>(<TT>HierNode</TT>) and a <TT>MobileNode</TT>. The basestation node isresponsible for delivering packets into and out of the wirelessdomain. In order to achieve this we need Hierarchical routing. <P>Each wireless domain along with its base-station would have an uniquedomain address assigned to them. All packets destined to a wirelessnode would reach the base-station attached to the domain of thatwireless node, who would eventually hand the packetover to the destination (mobilenode). And mobilenodes route packets,destined to outside their (wireless) domain, to their base-stationnode. The base-station knows how to forward these packets towards the(wired) destination.<DIV ALIGN="CENTER"><A NAME="fig:mobilenode-basestation"></A><A NAME="6959"></A><TABLE><CAPTION ALIGN="BOTTOM"><STRONG>Figure 16.3:</STRONG>Schematic of a baseStationNode</CAPTION><TR><TD><DIV ALIGN="CENTER">basestation</DIV></TD></TR></TABLE></DIV>The schematic of a <TT>BaseStationNode</TT> is shown inFigure <A HREF="node191.html#fig:mobilenode-basestation" tppabs="http://www.isi.edu/nsnam/ns/doc/node191.html#fig:mobilenode-basestation">16.3</A>.<P>The mobilenodes in wired-cum-wireless scenario are required to supporthierarchical addressing/routing. Thus the <TT>MobileNode</TT> looksexactly like the <TT>BaseStationNode</TT>. The SRNode, however, simplyneeds to have its own hier-address since it does not require anyaddress demuxes and thus is not required to support hierrouting<A NAME="tex2html29" HREF="footnode.html#foot6966" tppabs="http://www.isi.edu/nsnam/ns/doc/footnode.html#foot6966"><SUP>16.2</SUP></A>.<P>The DSDV agent on having to forward a packet checks to see if thedestination is outside its (wireless) subnet. If so, it tries toforward the packet to its base-station node. In case no route tobase-station is found the packet is dropped. Otherwise thepacket is forwarded to the next_hop towards the base-station. Whichis then routed towards the wired network by base-station'sclassifiers.<P>The DSR agent, on receiving a pkt destined outside its subnet, sendsout a route-query for its base-station in case the route tobase-station is not known. The data pkt is temporarily cached while itwaits to hear route replies from base-station. On getting a reply thepacket is provided with routing information in its header and sendaway towards the base-station. The base-station address demuxes routesit correctly toward the wired network.<P>The example script for a wired-cum-wireless simulation can be found attcl/ex/wired-cum-wireless-sim.tcl. The methods forwired-cum-wireless implementations are defined intcl/lib/ns-bsnode.tcl, tcl/mobility/{com.tcl,dsr.tcl, dsdv.tcl}, dsdv/dsdv.{cc,h} anddsr/dsragent.{cc,h}.<P><HR><!--Navigation Panel--><A NAME="tex2html4211" HREF="node192.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node192.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html4205" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html4199" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html4207" 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="tex2html4209" 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="tex2html4212" HREF="node192.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node192.html">16.2.2 MobileIP</A><B> Up:</B> <A NAME="tex2html4206" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html">16.2 Extensions made to</A><B> Previous:</B> <A NAME="tex2html4200" HREF="node190.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node190.html">16.2 Extensions made to</A>   <B> <A NAME="tex2html4208" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html4210" 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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