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This is a LOT of overhead, and will increase as moreprotocols are added into ns.For ``packet-intensive'' simulations, this could be a huge overhead.For instance, as of now (Aug 30, 2000), the size of packet headers ofall protocols in ns is about 1.9KB; however, if you turn on only thecommon header, the IP header and the TCP header, they add up to about100 bytes. If you are doing large-scale web traffic simulation with many big fatpipes, reducing unused packet headers can lead to major memorysaving.<P>To include only the packet headers that are of interest to you in your specific simulation, follow this pattern (e.g., you want to remove AODVand ARP headers from your simulation):<PRE> remove-packet-header AODV ARP ...... set ns [new Simulator]</PRE>Notice that <TT>remove-packet-header</TT> MUST go before the simulatoris created.All packet header names are in the forms of<TT>PacketHeader/[hdr]</TT>. You only need to supply the <TT>[hdr]</TT> part, not the prefix.To find the names of packet headers, you may either look them up in tcl/lib/ns-packet.tcl, or run the following simple commands in: <PRE> foreach cl [PacketHeader info subclass] { puts $cl }</PRE> <P>To include only a specific set of headers in your simulation, e.g., IPand TCP, follow this pattern:<PRE> remove-all-packet-headers add-packet-header IP TCP ...... set ns [new Simulator]</PRE>IMPORTANT: You MUST never remove common header from yoursimulation. As you can see in tcl/lib/ns-packet.tcl, this is enforcedby these header manipulation procs.<P><EM>Notice that by default, all packet headers are included</EM>.<P><HR><!--Navigation Panel--><A NAME="tex2html3288" HREF="node131.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node131.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html3282" HREF="node128.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node128.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html3278" HREF="node129.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node129.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html3284" 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="tex2html3286" 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="tex2html3289" HREF="node131.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node131.html">12.2 Packet Classes</A><B> Up:</B> <A NAME="tex2html3283" HREF="node128.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node128.html">12.1 A Protocol-Specific Packet</A><B> Previous:</B> <A NAME="tex2html3279" HREF="node129.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node129.html">12.1.1 Adding a New</A>   <B> <A NAME="tex2html3285" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html3287" 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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