136 lines
3.5 KiB
HTML
136 lines
3.5 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 PBFIFO</TITLE>
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</HEAD><BODY>
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<H1>PBFIFO</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 - Packet limited First In, First Out queue
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<P>
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bfifo - Byte limited First In, First Out queue
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<P>
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>tc qdisc ... add pfifo</B>
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<B>[ limit</B>
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packets
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<B>]</B>
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<P>
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<B>tc qdisc ... add bfifo</B>
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<B>[ limit</B>
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bytes
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<B>]</B>
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<P>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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The pfifo and bfifo qdiscs are unadorned First In, First Out queues. They are the
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simplest queues possible and therefore have no overhead.
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<B>pfifo</B>
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constrains the queue size as measured in packets.
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<B>bfifo</B>
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does so as measured in bytes.
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<P>
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Like all non-default qdiscs, they maintain statistics. This might be a reason to prefer
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pfifo or bfifo over the default.
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<P>
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<A NAME="lbAE"> </A>
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<H2>ALGORITHM</H2>
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A list of packets is maintained, when a packet is enqueued it gets inserted at the tail of
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a list. When a packet needs to be sent out to the network, it is taken from the head of the list.
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<P>
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If the list is too long, no further packets are allowed on. This is called 'tail drop'.
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<P>
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<A NAME="lbAF"> </A>
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<H2>PARAMETERS</H2>
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<DL COMPACT>
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<DT id="1">limit<DD>
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Maximum queue size. Specified in bytes for bfifo, in packets for pfifo. For pfifo, defaults
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to the interface txqueuelen, as 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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The range for this parameter is [0, UINT32_MAX].
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<P>
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For bfifo, it defaults to the txqueuelen multiplied by the interface MTU.
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The range for this parameter is [0, UINT32_MAX] bytes.
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<P>
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Note: The link layer header was considered when counting packets length.
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<P>
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</DL>
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<A NAME="lbAG"> </A>
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<H2>OUTPUT</H2>
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The output of
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<B>tc -s qdisc ls</B>
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contains the limit, either in packets or in bytes, and the number of bytes
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and packets actually sent. An unsent and dropped packet only appears between braces
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and is not counted as 'Sent'.
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<P>
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In this example, the queue length is 100 packets, 45894 bytes were sent over 681 packets.
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No packets were dropped, and as the pfifo queue does not slow down packets, there were also no
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overlimits:
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<P>
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<PRE>
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# tc -s qdisc ls dev eth0
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qdisc pfifo 8001: dev eth0 limit 100p
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Sent 45894 bytes 681 pkts (dropped 0, overlimits 0)
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</PRE>
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<P>
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If a backlog occurs, this is displayed as well.
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<A NAME="lbAH"> </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="lbAI"> </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">SYNOPSIS</A><DD>
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<DT id="4"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="5"><A HREF="#lbAE">ALGORITHM</A><DD>
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<DT id="6"><A HREF="#lbAF">PARAMETERS</A><DD>
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<DT id="7"><A HREF="#lbAG">OUTPUT</A><DD>
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<DT id="8"><A HREF="#lbAH">SEE ALSO</A><DD>
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<DT id="9"><A HREF="#lbAI">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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