tc-pfifo_fast(8) — Linux manual page

PFIFO_FAST(8)                     Linux                    PFIFO_FAST(8)

NAME

       pfifo_fast - three-band first in, first out queue

DESCRIPTION

       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.

ALGORITHM

       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.

PARAMETERS

       txqueuelen
              The length of the three bands depends on the interface
              txqueuelen, as specified with ip(8).

BUGS

       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.

SEE ALSO

       tc(8)

AUTHORS

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

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

COLOPHON

       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
       2024-06-14.  (At that time, the date of the most recent commit
       that was found in the repository was 2024-06-11.)  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 man-pages@man7.org

iproute2                     10 January 2002               PFIFO_FAST(8)

Pages that refer to this page: tc(8)

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