# phpman > man > PFIFO_FAST(8)

[PFIFO_FAST(8)](https://www.chedong.com/phpMan.php/man/PFIFOFAST/8/markdown)                                   Linux                                  [PFIFO_FAST(8)](https://www.chedong.com/phpMan.php/man/PFIFOFAST/8/markdown)



## NAME
       pfifo_fast - three-band first in, first out queue


## DESCRIPTION
       pfifo_fast is the default qdisc of each interface.

       Whenever  an  interface is created, the pfifo_fast qdisc is automatically used as a queue. If
       another qdisc is attached, it preempts the default pfifo_fast, which automatically returns to
       function when an existing qdisc is detached.

       In this sense this qdisc is magic, and unlike other qdiscs.


## ALGORITHM
       The  algorithm  is very similar to that of the classful [**tc-prio**(8)](https://www.chedong.com/phpMan.php/man/tc-prio/8/markdown) qdisc.  **pfifo**___**fast** is like
       three [**tc-pfifo**(8)](https://www.chedong.com/phpMan.php/man/tc-pfifo/8/markdown) queues side by side, where packets can be enqueued  in  any  of  the  three
       bands based on their Type of Service bits or assigned priority.

       Not all three bands are dequeued simultaneously - as long as lower bands have traffic, higher
       bands are never dequeued. This can be used to  prioritize  interactive  traffic  or  penalize
       'lowest cost' traffic.

       Each  band  can  be  txqueuelen packets long, as configured with [**ifconfig**(8)](https://www.chedong.com/phpMan.php/man/ifconfig/8/markdown) or [**ip**(8)](https://www.chedong.com/phpMan.php/man/ip/8/markdown).  Addi‐
       tional packets coming in are not enqueued but are instead dropped.

       See [**tc-prio**(8)](https://www.chedong.com/phpMan.php/man/tc-prio/8/markdown) for complete details on how TOS bits are translated into bands.

## PARAMETERS
       txqueuelen
              The length of the three bands depends on the interface txqueuelen, as  specified  with
              [**ifconfig**(8)](https://www.chedong.com/phpMan.php/man/ifconfig/8/markdown) or [**ip**(8)](https://www.chedong.com/phpMan.php/man/ip/8/markdown).


## BUGS
       Does  not  maintain statistics and does not show up in tc qdisc ls. This is because it is the
       automatic default in the absence of a configured qdisc.


## SEE ALSO
       [**tc**(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)


## AUTHORS
       Alexey N. Kuznetsov, <<kuznet@ms2.inr.ac.ru>>

       This manpage maintained by bert hubert <<ahu@ds9a.nl>>



iproute2                                   10 January 2002                             [PFIFO_FAST(8)](https://www.chedong.com/phpMan.php/man/PFIFOFAST/8/markdown)