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1 | .TH PFIFO_FAST 8 "10 January 2002" "iproute2" "Linux" |
2 | .SH NAME | |
3 | pfifo_fast \- three-band first in, first out queue | |
4 | ||
5 | .SH DESCRIPTION | |
6 | pfifo_fast is the default qdisc of each interface. | |
7 | ||
8 | Whenever an interface is created, the pfifo_fast qdisc is automatically used | |
9 | as a queue. If another qdisc is attached, it preempts the default | |
10 | pfifo_fast, which automatically returns to function when an existing qdisc | |
11 | is detached. | |
12 | ||
13 | In this sense this qdisc is magic, and unlike other qdiscs. | |
14 | ||
15 | .SH ALGORITHM | |
16 | The algorithm is very similar to that of the classful | |
17 | .BR tc-prio (8) | |
18 | qdisc. | |
19 | .B pfifo_fast | |
20 | is like three | |
21 | .BR tc-pfifo (8) | |
22 | queues side by side, where packets can be enqueued in any of the three bands | |
23 | based on their Type of Service bits or assigned priority. | |
24 | ||
25 | Not all three bands are dequeued simultaneously - as long as lower bands | |
26 | have traffic, higher bands are never dequeued. This can be used to | |
27 | prioritize interactive traffic or penalize 'lowest cost' traffic. | |
28 | ||
29 | Each band can be txqueuelen packets long, as configured with | |
30 | .BR ifconfig (8) | |
31 | or | |
32 | .BR ip (8). | |
33 | Additional packets coming in are not enqueued but are instead dropped. | |
34 | ||
35 | See | |
36 | .BR tc-prio (8) | |
37 | for complete details on how TOS bits are translated into bands. | |
38 | .SH PARAMETERS | |
39 | .TP | |
40 | txqueuelen | |
41 | The length of the three bands depends on the interface txqueuelen, as | |
42 | specified with | |
43 | .BR ifconfig (8) | |
44 | or | |
45 | .BR ip (8). | |
46 | ||
47 | .SH BUGS | |
48 | Does not maintain statistics and does not show up in tc qdisc ls. This is because | |
49 | it is the automatic default in the absence of a configured qdisc. | |
50 | ||
51 | .SH SEE ALSO | |
52 | .BR tc (8) | |
53 | ||
54 | .SH AUTHORS | |
55 | Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru> | |
56 | ||
57 | This manpage maintained by bert hubert <ahu@ds9a.nl> | |
58 | ||
59 |