tc-pfifo_fast

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 automati-
       cally 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 ifcon-
       fig(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 txqueue-
	      len, 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, <kuznet@ms2.inr.ac.ru>

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





iproute2		       10 January 2002			PFIFO_FAST(8)