tc-bfifo(8) — Linux manual page


PBFIFO(8)                         Linux                        PBFIFO(8)

NAME         top

       pfifo - Packet limited First In, First Out queue

       bfifo - Byte limited First In, First Out queue

SYNOPSIS         top

       tc qdisc ... add pfifo [ limit packets ]

       tc qdisc ... add bfifo [ limit bytes ]

DESCRIPTION         top

       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         top

       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         top

       limit  Maximum queue size. Specified in bytes for bfifo, in
              packets for pfifo. For pfifo, defaults to the interface
              txqueuelen, as specified with ip(8).  The range for this
              parameter is [0, UINT32_MAX].

              For bfifo, it defaults to the txqueuelen multiplied by the
              interface MTU.  The range for this parameter is [0,
              UINT32_MAX] bytes.

              Note: The link layer header was considered when counting
              packets length.

OUTPUT         top

       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 packets, there were also no

       # 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         top


AUTHORS         top

       Alexey N. Kuznetsov, <>

       This manpage maintained by bert hubert <>

COLOPHON         top

       This page is part of the iproute2 (utilities for controlling
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iproute2                     10 January 2002                   PBFIFO(8)

Pages that refer to this page: tc(8)tc-htb(8)tc-pfifo_fast(8)