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 ifconfig(8) or 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 ifconfig(8) or 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.
Alexey N. Kuznetsov, <firstname.lastname@example.org> This manpage maintained by bert hubert <email@example.com>
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 firstname.lastname@example.org, email@example.com. This page was obtained from the project's upstream Git repository ⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on 2021-08-27. (At that time, the date of the most recent commit that was found in the repository was 2021-08-18.) 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 firstname.lastname@example.org iproute2 10 January 2002 PFIFO_FAST(8)
Pages that refer to this page: tc(8)