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PBFIFO
!!!PBFIFO
NAME
SYNOPSIS
DESCRIPTION
ALGORITHM
PARAMETERS
OUTPUT
SEE ALSO
AUTHORS
----
!!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(8) or
ip(8).


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 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)
!!AUTHORS


Alexey N. Kuznetsov,


This manpage maintained by bert hubert
----

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Last edited on Tuesday, June 4, 2002 12:31:20 am by "perry"

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