1PFIFO_FAST(8) Linux PFIFO_FAST(8)
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6 pfifo_fast - three-band first in, first out queue
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10 pfifo_fast is the default qdisc of each interface.
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12 Whenever an interface is created, the pfifo_fast qdisc is automatically
13 used as a queue. If another qdisc is attached, it preempts the default
14 pfifo_fast, which automatically returns to function when an existing
15 qdisc is detached.
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17 In this sense this qdisc is magic, and unlike other qdiscs.
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21 The algorithm is very similar to that of the classful tc-prio(8) qdisc.
22 pfifo_fast is like three tc-pfifo(8) queues side by side, where packets
23 can be enqueued in any of the three bands based on their Type of Ser‐
24 vice bits or assigned priority.
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26 Not all three bands are dequeued simultaneously - as long as lower
27 bands have traffic, higher bands are never dequeued. This can be used
28 to prioritize interactive traffic or penalize 'lowest cost' traffic.
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30 Each band can be txqueuelen packets long, as configured with ifcon‐
31 fig(8) or ip(8). Additional packets coming in are not enqueued but are
32 instead dropped.
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34 See tc-prio(8) for complete details on how TOS bits are translated into
35 bands.
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38 txqueuelen
39 The length of the three bands depends on the interface txqueue‐
40 len, as specified with ifconfig(8) or ip(8).
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44 Does not maintain statistics and does not show up in tc qdisc ls. This
45 is because it is the automatic default in the absence of a configured
46 qdisc.
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50 tc(8)
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54 Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>
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56 This manpage maintained by bert hubert <ahu@ds9a.nl>
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60iproute2 10 January 2002 PFIFO_FAST(8)