109 lines
3.1 KiB
HTML
109 lines
3.1 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of PFIFO_FAST</TITLE>
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</HEAD><BODY>
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<H1>PFIFO_FAST</H1>
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Section: Linux (8)<BR>Updated: 10 January 2002<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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pfifo_fast - three-band first in, first out queue
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<P>
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<A NAME="lbAC"> </A>
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<H2>DESCRIPTION</H2>
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pfifo_fast is the default qdisc of each interface.
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<P>
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Whenever an interface is created, the pfifo_fast qdisc is automatically used
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as a queue. If another qdisc is attached, it preempts the default
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pfifo_fast, which automatically returns to function when an existing qdisc
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is detached.
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<P>
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In this sense this qdisc is magic, and unlike other qdiscs.
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<P>
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<A NAME="lbAD"> </A>
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<H2>ALGORITHM</H2>
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The algorithm is very similar to that of the classful
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<B><A HREF="/cgi-bin/man/man2html?8+tc-prio">tc-prio</A></B>(8)
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qdisc.
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<B>pfifo_fast</B>
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is like three
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<B><A HREF="/cgi-bin/man/man2html?8+tc-pfifo">tc-pfifo</A></B>(8)
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queues side by side, where packets can be enqueued in any of the three bands
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based on their Type of Service bits or assigned priority.
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<P>
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Not all three bands are dequeued simultaneously - as long as lower bands
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have traffic, higher bands are never dequeued. This can be used to
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prioritize interactive traffic or penalize 'lowest cost' traffic.
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<P>
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Each band can be txqueuelen packets long, as configured with
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<B><A HREF="/cgi-bin/man/man2html?8+ifconfig">ifconfig</A></B>(8)
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or
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<B><A HREF="/cgi-bin/man/man2html?8+ip">ip</A></B>(8).
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Additional packets coming in are not enqueued but are instead dropped.
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<P>
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See
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<B><A HREF="/cgi-bin/man/man2html?8+tc-prio">tc-prio</A></B>(8)
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for complete details on how TOS bits are translated into bands.
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<A NAME="lbAE"> </A>
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<H2>PARAMETERS</H2>
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<DL COMPACT>
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<DT id="1">txqueuelen<DD>
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The length of the three bands depends on the interface txqueuelen, as
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specified with
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<B><A HREF="/cgi-bin/man/man2html?8+ifconfig">ifconfig</A></B>(8)
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or
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<B><A HREF="/cgi-bin/man/man2html?8+ip">ip</A></B>(8).
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<P>
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</DL>
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<A NAME="lbAF"> </A>
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<H2>BUGS</H2>
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Does not maintain statistics and does not show up in tc qdisc ls. This is because
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it is the automatic default in the absence of a configured qdisc.
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<P>
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<A NAME="lbAG"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?8+tc">tc</A></B>(8)
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<P>
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<A NAME="lbAH"> </A>
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<H2>AUTHORS</H2>
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Alexey N. Kuznetsov, <<A HREF="mailto:kuznet@ms2.inr.ac.ru">kuznet@ms2.inr.ac.ru</A>>
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<P>
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This manpage maintained by bert hubert <<A HREF="mailto:ahu@ds9a.nl">ahu@ds9a.nl</A>>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="2"><A HREF="#lbAB">NAME</A><DD>
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<DT id="3"><A HREF="#lbAC">DESCRIPTION</A><DD>
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<DT id="4"><A HREF="#lbAD">ALGORITHM</A><DD>
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<DT id="5"><A HREF="#lbAE">PARAMETERS</A><DD>
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<DT id="6"><A HREF="#lbAF">BUGS</A><DD>
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<DT id="7"><A HREF="#lbAG">SEE ALSO</A><DD>
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<DT id="8"><A HREF="#lbAH">AUTHORS</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:06:17 GMT, March 31, 2021
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</BODY>
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