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1 perry 1 PBFIFO
2 !!!PBFIFO
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 ALGORITHM
7 PARAMETERS
8 OUTPUT
9 SEE ALSO
10 AUTHORS
11 ----
12 !!NAME
13
14
15 pfifo - Packet limited First In, First Out queue
16
17
18 bfifo - Byte limited First In, First Out queue
19 !!SYNOPSIS
20
21
22 __tc qdisc ... add pfifo [[ limit__ packets
23 __]__
24
25
26 __tc qdisc ... add bfifo [[ limit__ bytes
27 __]__
28 !!DESCRIPTION
29
30
31 The pfifo and bfifo qdiscs are unadorned First In, First Out
32 queues. They are the simplest queues possible and therefore
33 have no overhead. __pfifo__ constrains the queue size as
34 measured in packets. __bfifo__ does so as measured in
35 bytes.
36
37
38 Like all non-default qdiscs, they maintain statistics. This
39 might be a reason to prefer pfifo or bfifo over the
40 default.
41 !!ALGORITHM
42
43
44 A list of packets is maintained, when a packet is enqueued
45 it gets inserted at the tail of a list. When a packet needs
46 to be sent out to the network, it is taken from the head of
47 the list.
48
49
50 If the list is too long, no further packets are allowed on.
51 This is called 'tail drop'.
52 !!PARAMETERS
53
54
55 limit
56
57
58 Maximum queue size. Specified in bytes for bfifo, in packets
59 for pfifo. For pfifo, defaults to the interface txqueuelen,
60 as specified with ifconfig(8) or
61 ip(8).
62
63
64 For bfifo, it defaults to the txqueuelen multiplied by the
65 interface MTU.
66 !!OUTPUT
67
68
69 The output of __tc -s qdisc ls__ contains the limit,
70 either in packets or in bytes, and the number of bytes and
71 packets actually sent. An unsent and dropped packet only
72 appears between braces and is not counted as
73 'Sent'.
74
75
76 In this example, the queue length is 100 packets, 45894
77 bytes were sent over 681 packets. No packets were dropped,
78 and as the pfifo queue does not slow down packets, there
79 were also no overlimits:
80
81
82 # tc -s qdisc ls dev eth0
83 qdisc pfifo 8001: dev eth0 limit 100p
84 Sent 45894 bytes 681 pkts (dropped 0, overlimits 0)
85 If a backlog occurs, this is displayed as well.
86 !!SEE ALSO
87
88
89 tc(8)
90 !!AUTHORS
91
92
93 Alexey N. Kuznetsov,
94
95
96 This manpage maintained by bert hubert
97 ----
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