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58 lines
1.6 KiB
Groff
58 lines
1.6 KiB
Groff
.TH PFIFO_FAST 8 "10 January 2002" "iproute2" "Linux"
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.SH NAME
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pfifo_fast \- three-band first in, first out queue
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.SH DESCRIPTION
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pfifo_fast is the default qdisc of each interface.
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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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In this sense this qdisc is magic, and unlike other qdiscs.
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.SH ALGORITHM
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The algorithm is very similar to that of the classful
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.BR tc-prio (8)
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qdisc.
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.B pfifo_fast
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is like three
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.BR tc-pfifo (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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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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Each band can be txqueuelen packets long, as configured with
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.BR ifconfig (8)
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or
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.BR ip (8).
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Additional packets coming in are not enqueued but are instead dropped.
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See
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.BR tc-prio (8)
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for complete details on how TOS bits are translated into bands.
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.SH PARAMETERS
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.TP
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txqueuelen
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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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.BR ifconfig (8)
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or
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.BR ip (8).
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.SH BUGS
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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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.SH SEE ALSO
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.BR tc (8)
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.SH AUTHORS
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Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>
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This manpage maintained by bert hubert <ahu@ds9a.nl>
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