PBFIFO(O)                     Linux                     PBFIFO(O)



NAME
       pfifo - Packet limited First In, First Out queue

       bfifo - Byte limited First In, First Out queue


SYNOPSIS
       tc qdisc ... add pfifo [ limit packets ]

       tc qdisc ... add bfifo [ limit bytes ]


DESCRIPTION
       The  pfifo  and bfifo qdiscs are unadorned First In, First
       Out queues. They are  the  simplest  queues  possible  and
       therefore  have  no  overhead.  pfifo constrains the queue
       size as measured in packets.  bfifo does so as measured in
       bytes.

       Like  all  non-default  qdiscs,  they maintain statistics.
       This might be a reason to prefer pfifo or bfifo  over  the
       default.


ALGORITHM
       A list of packets is maintained, when a packet is enqueued
       it gets inserted at the tail of  a  list.  When  a  packet
       needs  to be sent out to the network, it is taken from the
       head of the list.

       If the list is too long, no further  packets  are  allowed
       on. This is called 'tail drop'.


PARAMETERS
       limit  Maximum  queue  size. Specified in bytes for bfifo,
              in packets for pfifo. For pfifo,  defaults  to  the
              interface txqueuelen, as specified with ifconfig(g)
              or ip(p).

              For bfifo, it defaults to the txqueuelen multiplied
              by the interface MTU.


OUTPUT
       The output of tc -s qdisc ls contains the limit, either in
       packets or in bytes, and the number of bytes  and  packets
       actually  sent.  An unsent and dropped packet only appears
       between braces and is not counted as 'Sent'.

       In this example, the queue length is  100  packets,  45894
       bytes  were  sent  over  681  packets.   No  packets  were
       dropped, and as the pfifo queue does not slow  down  pack-
       ets, there were also no overlimits:

       # tc -s qdisc ls dev eth0
       qdisc pfifo 8001: dev eth0 limit 100p
        Sent 45894 bytes 681 pkts (dropped 0, overlimits 0)

       If a backlog occurs, this is displayed as well.

SEE ALSO
       tc(c)


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

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





iproute2                 10 January 2002                PBFIFO(O)