tc-pfifo(8)

1PBFIFO(8)                            Linux                           PBFIFO(8)
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NAME

6       pfifo - Packet limited First In, First Out queue
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8       bfifo - Byte limited First In, First Out queue
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SYNOPSIS

12       tc qdisc ... add pfifo [ limit packets ]
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14       tc qdisc ... add bfifo [ limit bytes ]
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DESCRIPTION

18       The  pfifo  and  bfifo qdiscs are unadorned First In, First Out queues.
19       They are the simplest queues possible and therefore have  no  overhead.
20       pfifo  constrains the queue size as measured in packets.  bfifo does so
21       as measured in bytes.
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23       Like all non-default qdiscs, they maintain statistics. This might be  a
24       reason to prefer pfifo or bfifo over the default.
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ALGORITHM

28       A  list  of  packets  is  maintained, when a packet is enqueued it gets
29       inserted at the tail of a list. When a packet needs to be sent  out  to
30       the network, it is taken from the head of the list.
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32       If  the  list  is  too long, no further packets are allowed on. This is
33       called 'tail drop'.
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PARAMETERS

37       limit  Maximum queue size. Specified in bytes for bfifo, in packets for
38              pfifo. For pfifo, defaults to the interface txqueuelen, as spec‐
39              ified with ifconfig(8) or ip(8).
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41              For bfifo, it defaults  to  the  txqueuelen  multiplied  by  the
42              interface MTU.
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OUTPUT

46       The  output  of tc -s qdisc ls contains the limit, either in packets or
47       in bytes, and the number of bytes and packets actually sent. An  unsent
48       and  dropped  packet  only appears between braces and is not counted as
49       'Sent'.
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51       In this example, the queue length is 100 packets, 45894 bytes were sent
52       over 681 packets.  No packets were dropped, and as the pfifo queue does
53       not slow down packets, there were also no overlimits:
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55       # tc -s qdisc ls dev eth0
56       qdisc pfifo 8001: dev eth0 limit 100p
57        Sent 45894 bytes 681 pkts (dropped 0, overlimits 0)
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59       If a backlog occurs, this is displayed as well.
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AUTHORS

66       Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>
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68       This manpage maintained by bert hubert <ahu@ds9a.nl>
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74iproute2                        10 January 2002                      PBFIFO(8)