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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>7. Queue Management and Packet Scheduling</TITLE><META NAME="description" CONTENT="7. Queue Management and Packet Scheduling"><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="node88.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node88.html"><LINK REL="previous" HREF="node57.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node57.html"><LINK REL="up" HREF="node29.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node29.html"><LINK REL="next" HREF="node65.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node65.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html2283" HREF="node65.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node65.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html2277" HREF="node29.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node29.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html2271" HREF="node63.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node63.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html2279" 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="tex2html2281" 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="tex2html2284" HREF="node65.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node65.html">7.1 The C++ Queue</A><B> Up:</B> <A NAME="tex2html2278" HREF="node29.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node29.html">2 Simulator Basics</A><B> Previous:</B> <A NAME="tex2html2272" HREF="node63.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node63.html">6.4 Commands at a</A>   <B> <A NAME="tex2html2280" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html2282" 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="SECTION03400000000000000000"></A><A NAME="chap:qmgmt"></A><BR>7. Queue Management and Packet Scheduling</H1><P>Queues represent locations where packets may be held (or dropped).Packet scheduling refers to the decision process used to choosewhich packets should be serviced or dropped.Buffer management refers to any particular discipline usedto regulate the occupancy of a particular queue.At present, support is included for drop-tail (FIFO) queueing,RED buffer management, CBQ (including a priority and round-robin scheduler), andvariants of Fair Queueing including, Fair Queueing (FQ),Stochastic Fair Queueing (SFQ), and Deficit Round-Robin (DRR).In the common case where a <EM>delay</EM> element is downstream froma queue, the queue may be <EM>blocked</EM> until it is re-enabledby its downstream neighbor.This is the mechanism by which transmission delay is simulated.In addition, queues may be forcibly blocked or unblocked at arbitrarytimes by their neighbors (which is used to implement multi-queueaggregate queues with inter-queue flow control).Packet drops are implemented in such a way that queues containa ``drop destination''; that is, an object that receives all packetsdropped by a queue.This can be useful to (for example) keep statistics on dropped packets.<P><BR><HR><!--Table of Child-Links--><A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A><UL><LI><A NAME="tex2html2285" HREF="node65.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node65.html">7.1 The C++ Queue Class</A><UL><LI><A NAME="tex2html2286" HREF="node66.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node66.html">7.1.1 Queue blocking</A><LI><A NAME="tex2html2287" HREF="node67.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node67.html">7.1.2 PacketQueue Class</A></UL><BR><LI><A NAME="tex2html2288" HREF="node68.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node68.html">7.2 Example: Drop Tail</A><LI><A NAME="tex2html2289" HREF="node69.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node69.html">7.3 Different types of Queue objects</A><LI><A NAME="tex2html2290" HREF="node70.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node70.html">7.4 Commands at a glance</A><LI><A NAME="tex2html2291" HREF="node71.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node71.html">7.5 Queue/JoBS</A><UL><LI><A NAME="tex2html2292" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html">7.5.1 The JoBS algorithm</A><UL><LI><A NAME="tex2html2293" HREF="node73.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node73.html">7.5.1.1 Objective</A><LI><A NAME="tex2html2294" HREF="node74.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node74.html">7.5.1.2 Mechanisms</A></UL><LI><A NAME="tex2html2295" HREF="node75.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node75.html">7.5.2 Configuration</A><UL><LI><A NAME="tex2html2296" HREF="node76.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node76.html">7.5.2.1 Initial Setup</A><LI><A NAME="tex2html2297" HREF="node77.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node77.html">7.5.2.2 Creating the JoBS links</A><LI><A NAME="tex2html2298" HREF="node78.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node78.html">7.5.2.3 Marking the traffic</A></UL><LI><A NAME="tex2html2299" HREF="node79.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node79.html">7.5.3 Tracing</A><LI><A NAME="tex2html2300" HREF="node80.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node80.html">7.5.4 Variables</A><UL><LI><A NAME="tex2html2301" HREF="node81.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node81.html">7.5.4.1 JoBS objects</A><LI><A NAME="tex2html2302" HREF="node82.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node82.html">7.5.4.2 Marker objects</A><LI><A NAME="tex2html2303" HREF="node83.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node83.html">7.5.4.3 Demarker objects</A></UL><LI><A NAME="tex2html2304" HREF="node84.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node84.html">7.5.5 Commands at a glance</A><UL><LI><A NAME="tex2html2305" HREF="node85.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node85.html">7.5.5.1 JoBS objects</A><LI><A NAME="tex2html2306" HREF="node86.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node86.html">7.5.5.2 Marker objects</A><LI><A NAME="tex2html2307" HREF="node87.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node87.html">7.5.5.3 Demarker objects</A></UL></UL></UL><!--End of Table of Child-Links--><HR><!--Navigation Panel--><A NAME="tex2html2283" HREF="node65.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node65.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html2277" HREF="node29.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node29.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html2271" HREF="node63.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node63.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html2279" 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="tex2html2281" 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="tex2html2284" HREF="node65.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node65.html">7.1 The C++ Queue</A><B> Up:</B> <A NAME="tex2html2278" HREF="node29.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node29.html">2 Simulator Basics</A><B> Previous:</B> <A NAME="tex2html2272" HREF="node63.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node63.html">6.4 Commands at a</A>   <B> <A NAME="tex2html2280" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html2282" 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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