| .TH PFIFO_FAST 8 "10 January 2002" "iproute2" "Linux" |
| .SH NAME |
| pfifo_fast \- three-band first in, first out queue |
| |
| .SH 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. |
| |
| .SH ALGORITHM |
| The algorithm is very similar to that of the classful |
| .BR tc-prio (8) |
| qdisc. |
| .B pfifo_fast |
| is like three |
| .BR 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 |
| .BR ifconfig (8) |
| or |
| .BR ip (8). |
| Additional packets coming in are not enqueued but are instead dropped. |
| |
| See |
| .BR tc-prio (8) |
| for complete details on how TOS bits are translated into bands. |
| .SH PARAMETERS |
| .TP |
| txqueuelen |
| The length of the three bands depends on the interface txqueuelen, as |
| specified with |
| .BR ifconfig (8) |
| or |
| .BR ip (8). |
| |
| .SH 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. |
| |
| .SH SEE ALSO |
| .BR tc (8) |
| |
| .SH AUTHORS |
| Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru> |
| |
| This manpage maintained by bert hubert <ahu@ds9a.nl> |
| |
| |
