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 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) 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 config-
       ured qdisc.

SEE ALSO

       tc(8)

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)