PFIFO_FAST(8)                                                 Linux                                                PFIFO_FAST(8)



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) qdisc.  pfifo_fast is like three tc-pfifo(8) queues side
       by  side,  where packets can be enqueued in any of the three bands based on their Type of Service bits or assigned prior-
       ity.

       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) or ip(8).  Additional packets coming in are not
       enqueued but are instead dropped.

       See tc-prio(8) 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) or ip(8).


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)


AUTHORS
       Alexey N. Kuznetsov, <kuznetATms2.ru>

       This manpage maintained by bert hubert <ahuATds9a.nl>





iproute2                                                 10 January 2002                                           PFIFO_FAST(8)