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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>17.2.9 Integration with wired and wireless code</TITLE><META NAME="description" CONTENT="17.2.9 Integration with wired and wireless code"><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="node209.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node209.html"><LINK REL="previous" HREF="node207.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node207.html"><LINK REL="up" HREF="node199.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node199.html"><LINK REL="next" HREF="node209.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node209.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html4474" HREF="node209.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node209.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html4468" HREF="node199.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node199.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html4462" HREF="node207.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node207.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html4470" 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="tex2html4472" 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="tex2html4475" HREF="node209.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node209.html">17.2.10 Example scripts</A><B> Up:</B> <A NAME="tex2html4469" HREF="node199.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node199.html">17.2 Using the satellite</A><B> Previous:</B> <A NAME="tex2html4463" HREF="node207.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node207.html">17.2.8 support</A>   <B> <A NAME="tex2html4471" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html4473" 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="SECTION031429000000000000000"></A><A NAME="sec:satellite_usage_integration"></A><BR>17.2.9 Integration with wired and wireless code</H2><P>Recently (November 2001), support has been added to connect traditionalOTcl-based wired nodes with the satellite nodes. This section describesthe capabilities and limitations of that code.<P>The satellite code (and the wireless code) normally performs all routing in C++, while the traditional ns code uses a mix of OTcl and C++ code. For backward compatibility reasons, it is difficult to fully integrateboth the wired and wireless code. The strategy for integrating wireless and wired code has been to define a special gateway node (called a "basestation"), to use hierarchial routing, and to locate a single basestation node in the wireless network with a network stack located in both thewireless and the wired subnet. Because routing is not fully integrated, the topology of the simulation is limited to only one gateway node perwireless subnet (i.e., a packet cannot enter the wireless network from one wired gateway and leave via another).<P>The satellite/wired code integration takes a different strategy. Byselecting the node configuration<TT>$ns node-config -wiredRouting ON</TT> option, the C++routing in the satellite code is turned off, and instead, all satellite topology changes lead to upcalls into the OTcl code. As a result, the <TT>link_</TT> array in OTcl is manipulated according to all topology changes, and OTcl-based routing can occur. The penalty for doing this is a much longer execution time for larger simulations (such as Teledesic), but for smaller simulations, the difference is not as noticeable.<P>An example script detailing the use of this new option is shown intcl/ex/sat-wired.tcl, and a similar test in the satellite test suiteexercises this code. Additionally, all of the satellite example scriptsin tcl/ex directory can be converted to OTcl routing by using the <TT>$ns node-config -wiredRouting ON</TT> option. However, there are afew caveats: <UL><LI>The wired routing option for satellite has only been tested with(the default) static routing: <TT>$ns rtProto Static</TT>. The code triggersa global routing table update upon any satellite topology change.</LI><LI>The option <TT>data_driven_computation_</TT>can not be set to ``true'' when wiredRouting is ON. Note that the enablingor disabling of <TT>data_driven_computation_</TT> can give subtle differences in simulation output since routes are computed at different times (whilepropagation delays are continuously changing). This effect can be seenby toggling this parameter in the Iridium example script tcl/ex/sat-iridium.tcl.</LI><LI>In the trace file, when a packet is dropped due to ``no route tohost'' (such as when there is a topology change), the trace looks a bitdifferent depending on whether wiredRouting is turned OFF or ON. In theformer case, there is one line per drop, with the destination labelledas ``-2''. In the latter case, there are three events (enque ``+'', deque ``-'', and drop ``d'') corresponding to the same packet, and thedestination is shown as ``-1''. </LI><LI>In rare cases, there may be warning messages during the executionindicating ``node out of range.'' This can occur if a node becomesdisconnected in the topology and then another node tries to send a packetto it. For example, try enabling <TT>wiredRouting</TT> in the filetcl/ex/sat-mixed.tcl. This occurs because the routing table isdynamically sized upon topology change, and if a node becomes disconnected it may not have any entries inserted in the routing table (and hencethe routing table is not grown to accommodate its node number). Thiswarning should not affect actual trace output.</LI><LI>There has been no attempt to interoperate with wireless or mobile-IP code.</LI></UL><P><HR><!--Navigation Panel--><A NAME="tex2html4474" HREF="node209.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node209.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html4468" HREF="node199.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node199.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html4462" HREF="node207.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node207.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html4470" 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="tex2html4472" 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="tex2html4475" HREF="node209.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node209.html">17.2.10 Example scripts</A><B> Up:</B> <A NAME="tex2html4469" HREF="node199.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node199.html">17.2 Using the satellite</A><B> Previous:</B> <A NAME="tex2html4463" HREF="node207.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node207.html">17.2.8 support</A>   <B> <A NAME="tex2html4471" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html4473" 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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