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NAME | DESCRIPTION | ALGORITHM | PARAMETERS | BUGS | SEE ALSO | AUTHORS | COLOPHON |
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PFIFO_FAST(8) Linux PFIFO_FAST(8)
pfifo_fast - three-band first in, first out queue
pfifo_fast is the default qdisc of each interface.
Whenever an interface is created, the pfifo_fast qdisc is
automatically used as a queue. If another qdisc is attached, it
preempts the default pfifo_fast, which automatically returns to
function when an existing qdisc is detached.
In this sense this qdisc is magic, and unlike other qdiscs.
The algorithm is very similar to that of the classful tc-prio(8)
qdisc. pfifo_fast is like three tc-pfifo(8) queues side by side,
where packets can be enqueued in any of the three bands based on
their Type of Service bits or assigned priority.
Not all three bands are dequeued simultaneously - as long as lower
bands have traffic, higher bands are never dequeued. This can be
used to prioritize interactive traffic or penalize 'lowest cost'
traffic.
Each band can be txqueuelen packets long, as configured with
ip(8). Additional packets coming in are not enqueued but are
instead dropped.
See tc-prio(8) for complete details on how TOS bits are translated
into bands.
txqueuelen
The length of the three bands depends on the interface
txqueuelen, as specified with ip(8).
Does not maintain statistics and does not show up in tc qdisc ls.
This is because it is the automatic default in the absence of a
configured qdisc.
tc(8)
Alexey N. Kuznetsov, <[email protected]>
This manpage maintained by bert hubert <[email protected]>
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
[email protected], [email protected]. This page was
obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-08-08.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to [email protected]
iproute2 10 January 2002 PFIFO_FAST(8)
Pages that refer to this page: tc(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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