73 lines
1.9 KiB
Groff
73 lines
1.9 KiB
Groff
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.TH PBFIFO 8 "10 January 2002" "iproute2" "Linux"
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.SH NAME
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pfifo \- Packet limited First In, First Out queue
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.P
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bfifo \- Byte limited First In, First Out queue
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.SH SYNOPSIS
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.B tc qdisc ... add pfifo
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.B [ limit
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packets
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.B ]
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.P
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.B tc qdisc ... add bfifo
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.B [ limit
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bytes
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.B ]
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.SH DESCRIPTION
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The pfifo and bfifo qdiscs are unadorned First In, First Out queues. They are the
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simplest queues possible and therefore have no overhead.
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.B pfifo
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constrains the queue size as measured in packets.
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.B bfifo
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does so as measured in bytes.
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Like all non-default qdiscs, they maintain statistics. This might be a reason to prefer
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pfifo or bfifo over the default.
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.SH ALGORITHM
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A list of packets is maintained, when a packet is enqueued it gets inserted at the tail of
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a list. When a packet needs to be sent out to the network, it is taken from the head of the list.
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If the list is too long, no further packets are allowed on. This is called 'tail drop'.
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.SH PARAMETERS
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.TP
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limit
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Maximum queue size. Specified in bytes for bfifo, in packets for pfifo. For pfifo, defaults
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to the interface txqueuelen, as specified with
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.BR ifconfig (8)
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or
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.BR ip (8).
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For bfifo, it defaults to the txqueuelen multiplied by the interface MTU.
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.SH OUTPUT
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The output of
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.B tc -s qdisc ls
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contains the limit, either in packets or in bytes, and the number of bytes
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and packets actually sent. An unsent and dropped packet only appears between braces
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and is not counted as 'Sent'.
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In this example, the queue length is 100 packets, 45894 bytes were sent over 681 packets.
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No packets were dropped, and as the pfifo queue does not slow down packets, there were also no
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overlimits:
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.P
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.nf
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# tc -s qdisc ls dev eth0
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qdisc pfifo 8001: dev eth0 limit 100p
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Sent 45894 bytes 681 pkts (dropped 0, overlimits 0)
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.fi
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If a backlog occurs, this is displayed as well.
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.SH SEE ALSO
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.BR tc (8)
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.SH AUTHORS
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Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>
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This manpage maintained by bert hubert <ahu@ds9a.nl>
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