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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>14.7 LanRouter class</TITLE><META NAME="description" CONTENT="14.7 LanRouter class"><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="node159.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node159.html"><LINK REL="previous" HREF="node155.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node155.html"><LINK REL="up" HREF="node142.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node142.html"><LINK REL="next" HREF="node159.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node159.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html3704" HREF="node159.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node159.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html3698" HREF="node142.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node142.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html3692" HREF="node157.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node157.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html3700" 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="tex2html3702" 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="tex2html3705" HREF="node159.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node159.html">14.8 Other Components</A><B> Up:</B> <A NAME="tex2html3699" HREF="node142.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node142.html">14. Local Area Networks</A><B> Previous:</B> <A NAME="tex2html3693" HREF="node157.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node157.html">14.6.2 Example: Link Layer</A>   <B> <A NAME="tex2html3701" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html3703" 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="SECTION031170000000000000000">14.7 LanRouter class</A></H1>By default, there is just one <TT>LanRouter</TT> object per LAN, whichis created when a new <TT>LanNode</TT> is initialized. For every nodeon the LAN, the link layer object (<TT>LL</TT>) has a pointer to the<TT>LanRouter</TT>, so it is able to find the next hop for the packetthat is sent on the LAN:<PRE>Packet* LL::sendto(Packet* p, Handler* h){ int nh = (lanrouter_) ? lanrouter_-\>next_hop(p) : -1; . . .}</PRE><TT>LanRouter</TT> is able to find the next hop by querying the current<TT>RouteLogic</TT>:<PRE>int LanRouter::next_hop(Packet *p) { int next_hopIP; if (enableHrouting_) { routelogic_-\>lookup_hier(lanaddr_, adst, next_hopIP); } else { routelogic_-\>lookup_flat(lanaddr_, adst, next_hopIP); }</PRE>One limitation of this is that <TT>RouteLogic</TT> may not be aware ofdynamic changes to the routing. But it is always possible to derive anew class from <TT>LanRouter</TT> so that to re-define its<TT>next_hop</TT> method to handle dynamic changes appopriately.<P><BR><HR><ADDRESS>2003-09-23</ADDRESS></BODY></HTML>⌨️ 快捷键说明
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