# tc-pfifo(8) - man - phpman

[PBFIFO(8)](https://www.chedong.com/phpMan.php/man/PBFIFO/8/markdown)                                       Linux                                      [PBFIFO(8)](https://www.chedong.com/phpMan.php/man/PBFIFO/8/markdown)



## 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, de‐
              faults to the interface txqueuelen, as specified with [**ifconfig**(8)](https://www.chedong.com/phpMan.php/man/ifconfig/8/markdown) or [**ip**(8)](https://www.chedong.com/phpMan.php/man/ip/8/markdown).  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
       The  output of **tc** **-s** **qdisc** **ls** contains the limit, either in packets or in bytes, and the num‐
       ber 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
       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**(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)


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

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



iproute2                                   10 January 2002                                 [PBFIFO(8)](https://www.chedong.com/phpMan.php/man/PBFIFO/8/markdown)