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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>7.5.1.1 Objective</TITLE><META NAME="description" CONTENT="7.5.1.1 Objective"><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="node74.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node74.html"><LINK REL="previous" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html"><LINK REL="up" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html"><LINK REL="next" HREF="node74.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node74.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html2448" HREF="node74.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node74.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html2442" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html2436" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html2444" 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="tex2html2446" 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="tex2html2449" HREF="node74.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node74.html">7.5.1.2 Mechanisms</A><B> Up:</B> <A NAME="tex2html2443" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html">7.5.1 The JoBS algorithm</A><B> Previous:</B> <A NAME="tex2html2437" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html">7.5.1 The JoBS algorithm</A>   <B> <A NAME="tex2html2445" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html2447" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <BR><BR><!--End of Navigation Panel--><H3><A NAME="SECTION03451100000000000000">7.5.1.1 Objective</A></H3>The objective of the JoBS algorithm is to provide absolute andrelative (proportional) loss and delay differentiation independentlyat each node for <EM>classes</EM> of traffic. JoBS therefore providesservice guarantees on a <EM>per-hop</EM> basis. The set of performancerequirements are specified to the algorithm as a set of per-classQualtiy of Service (QoS) constraints. As an example, for threeclasses, the QoS constraints could be of the form:<UL><LI><!-- MATH $\mbox{Class-1 Delay} \approx 2 \cdot \mbox{Class-2 Delay}$ -->, </LI><LI><!-- MATH $\mbox{Class-2 Loss Rate} \approx 10^{-1} \cdot\mbox{Class-3 Loss Rate}$ -->, or </LI><LI><!-- MATH $\mbox{Class-3 Delay} \leq 5~ms$ -->. </LI></UL>Here, the first two constraints are relative constraints and the last one is an absolute constraint. The set of constraints can be any mix of relative and absolute constraints. More specifically, JoBS supports the five following types of constraints:<UL><LI><B>Relative delay constraints (RDC)</B> specify a proportional delay differentiation between classes. As an example, for two classes and , the RDC enforces a relationship<BR><P></P><DIV ALIGN="CENTER"><!-- MATH \begin{displaymath}\frac{\mbox{Delay of Class 2}}{\mbox{Delay of Class 1}}\approx \mbox{constant}\ .\nonumber\end{displaymath} --></DIV><BR CLEAR="ALL"><P></P></LI><LI><B>Absolute delay constraints (ADC)</B>: An ADC on class requires that the delays of class satisfy a worst-case bound .</LI><LI><B>Relative loss constraints (RLC)</B> specify a proportional loss differentiation between classes.</LI><LI><B>Absolute loss constraints (ALC)</B>: An ALC on class requires that the loss rate of class be bounded by an upper bound .</LI><LI><B>Absolute rate constraints (ARC)</B>: An ARC on class means that the throughput of class is bounded by a lower bound .</LI></UL><P>JoBS does not rely on admission control or traffic policing, nor does it make any assumption on traffic arrivals. Therefore, a system of constraints may become infeasible, and some constraints may need to be relaxed. QoS constraints are prioritized in the following order.<BR><P></P><DIV ALIGN="CENTER"><!-- MATH \begin{displaymath}\mbox{ALC} > \mbox{ADC, ARC} > \mbox{Relative Constraints} \ .\end{displaymath} --></DIV><BR CLEAR="ALL"><P></P>That is, if JoBS is unable to satisfy both absolute and relative constraints, it will give preference to the absolute constraints.<P><HR><!--Navigation Panel--><A NAME="tex2html2448" HREF="node74.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node74.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html2442" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html2436" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html2444" 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="tex2html2446" 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="tex2html2449" HREF="node74.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node74.html">7.5.1.2 Mechanisms</A><B> Up:</B> <A NAME="tex2html2443" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html">7.5.1 The JoBS algorithm</A><B> Previous:</B> <A NAME="tex2html2437" HREF="node72.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node72.html">7.5.1 The JoBS algorithm</A>   <B> <A NAME="tex2html2445" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html2447" 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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