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<A NAME="sec:diffservoverview"></A><BR>9.1 Overview</H1>
The DiffServ architecture provides QoS by
dividing traffic into different categories,
marking each packet with a code point that indicates its category,
and scheduling packets according accordingly.
The DiffServ module in can support four classes of traffic,
each of which has three dropping precedences allowing
differential treatment of traffic within a single class.
Packets in a single class of traffic are enqueued into
one corresponding physical RED queue,
which contains three virtual queues (one for each drop precedence).
Different RED parameters can be configured for virtual queues,
causing packets from one virtual queue to be dropped
more frequently than packets from another.
A packet with a lower dropping precedence is given
better treatment in times of congestion
because it is assigned a code point that corresponds to a virtual
queue with relatively lenient RED parameters.
The DiffServ module in has three major components:
<DL><DT><STRONG>Policy:</STRONG></DT><DD>Policy is specified by network administrator about
the level of service a class of traffic should receive in the network.
</DD><DT><STRONG>Edge router:</STRONG></DT><DD>Edge router marks packets with a code point according to the policy specified.
</DD><DT><STRONG>Core router:</STRONG></DT><DD>Core router examines packets' code point marking and forwarding them accordingly.
</DD></DL>
DiffServ attempts to restrict complexity to only the edge routers.<HR><!--Navigation Panel--><A NAME="tex2html2720" HREF="node93.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node93.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html2714" HREF="node91.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node91.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html2708" HREF="node91.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node91.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html2716" 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="tex2html2718" 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="tex2html2721" HREF="node93.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node93.html">9.2 Implementation</A><B> Up:</B> <A NAME="tex2html2715" HREF="node91.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node91.html">9. Differentiated Services Module</A><B> Previous:</B> <A NAME="tex2html2709" HREF="node91.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node91.html">9. Differentiated Services Module</A>   <B> <A NAME="tex2html2717" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html2719" 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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