1PFIFO_FAST(8)                        Linux                       PFIFO_FAST(8)
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NAME

6       pfifo_fast - three-band first in, first out queue
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DESCRIPTION

10       pfifo_fast is the default qdisc of each interface.
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12       Whenever an interface is created, the pfifo_fast qdisc is automatically
13       used as a queue. If another qdisc is attached, it preempts the  default
14       pfifo_fast,  which  automatically  returns to function when an existing
15       qdisc is detached.
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17       In this sense this qdisc is magic, and unlike other qdiscs.
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ALGORITHM

21       The algorithm is very similar to that of the classful tc-prio(8) qdisc.
22       pfifo_fast is like three tc-pfifo(8) queues side by side, where packets
23       can be enqueued in any of the three bands based on their Type  of  Ser‐
24       vice bits or assigned priority.
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26       Not  all  three  bands  are  dequeued simultaneously - as long as lower
27       bands have traffic, higher bands are never dequeued. This can  be  used
28       to prioritize interactive traffic or penalize 'lowest cost' traffic.
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30       Each  band  can  be  txqueuelen packets long, as configured with ifcon‐
31       fig(8) or ip(8).  Additional packets coming in are not enqueued but are
32       instead dropped.
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34       See tc-prio(8) for complete details on how TOS bits are translated into
35       bands.
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PARAMETERS

38       txqueuelen
39              The length of the three bands depends on the interface  txqueue‐
40              len, as specified with ifconfig(8) or ip(8).
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BUGS

44       Does  not maintain statistics and does not show up in tc qdisc ls. This
45       is because it is the automatic default in the absence of  a  configured
46       qdisc.
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SEE ALSO

50       tc(8)
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AUTHORS

54       Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>
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56       This manpage maintained by bert hubert <ahu@ds9a.nl>
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60iproute2                        10 January 2002                  PFIFO_FAST(8)