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NAME | SYNOPSIS | DESCRIPTION | ALGORITHM | PARAMETERS | OUTPUT | SEE ALSO | AUTHORS | COLOPHON |
PBFIFO(8) Linux PBFIFO(8)
pfifo - Packet limited First In, First Out queue
bfifo - Byte limited First In, First Out queue
tc qdisc ... add pfifo [ limit packets ]
tc qdisc ... add bfifo [ limit bytes ]
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.
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'.
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). 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.
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.
tc(8)
Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>
This manpage maintained by bert hubert <ahu@ds9a.nl>
This page is part of the iproute2 (utilities for controlling TCP/IP
networking and traffic) project. Information about the project can
be found at
⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
If you have a bug report for this manual page, send it to
netdev@vger.kernel.org, shemminger@osdl.org. This page was obtained
from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
2020-08-13. (At that time, the date of the most recent commit that
was found in the repository was 2020-06-24.) If you discover any
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corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
iproute2 10 January 2002 PBFIFO(8)