[mirror_iproute2.git] / man / man8 / tc-bfifo.8

.TH PBFIFO 8 "10 January 2002" "iproute2" "Linux"
.SH NAME
pfifo \- Packet limited First In, First Out queue
.P
bfifo \- Byte limited First In, First Out queue

.SH SYNOPSIS
.B tc qdisc ... add pfifo
.B [ limit
packets
.B ]
.P
.B tc qdisc ... add bfifo
.B [ limit
bytes
.B ]

.SH DESCRIPTION
The pfifo and bfifo qdiscs are unadorned First In, First Out queues. They are the
simplest queues possible and therefore have no overhead.
.B pfifo
constrains the queue size as measured in packets.
.B bfifo
does so as measured in bytes.

Like all non-default qdiscs, they maintain statistics. This might be a reason to prefer
pfifo or bfifo over the default.

.SH ALGORITHM
A list of packets is maintained, when a packet is enqueued it gets inserted at the tail of
a list. When a packet needs to be sent out to the network, it is taken from the head of the list.

If the list is too long, no further packets are allowed on. This is called 'tail drop'.

.SH PARAMETERS
.TP
limit
Maximum queue size. Specified in bytes for bfifo, in packets for pfifo. For pfifo, defaults
to the interface txqueuelen, as specified with
.BR ifconfig (8)
or
.BR ip (8).
The range for this parameter is [0, UINT32_MAX].

For bfifo, it defaults to the txqueuelen multiplied by the interface MTU.
The range for this parameter is [0, UINT32_MAX] bytes.

Note: The link layer header was considered when counting packets length.

.SH OUTPUT
The output of
.B tc -s qdisc ls
contains the limit, either in packets or in bytes, and the number of bytes
and packets actually sent. An unsent and dropped packet only appears between braces
and is not counted as 'Sent'.

In this example, the queue length is 100 packets, 45894 bytes were sent over 681 packets.
No packets were dropped, and as the pfifo queue does not slow down packets, there were also no
overlimits:
.P
.nf
# tc -s qdisc ls dev eth0
qdisc pfifo 8001: dev eth0 limit 100p
 Sent 45894 bytes 681 pkts (dropped 0, overlimits 0)
.fi

If a backlog occurs, this is displayed as well.
.SH SEE ALSO
.BR tc (8)

.SH AUTHORS
Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>

This manpage maintained by bert hubert <ahu@ds9a.nl>
Commit	Line	Data
09bba68c SH	1	.TH PBFIFO 8 "10 January 2002" "iproute2" "Linux"
	2	.SH NAME
	3	pfifo \- Packet limited First In, First Out queue
	4	.P
	5	bfifo \- Byte limited First In, First Out queue
	6
	7	.SH SYNOPSIS
	8	.B tc qdisc ... add pfifo
5699275b	9	.B [ limit
09bba68c SH	10	packets
	11	.B ]
	12	.P
	13	.B tc qdisc ... add bfifo
5699275b	14	.B [ limit
09bba68c SH	15	bytes
	16	.B ]
	17
	18	.SH DESCRIPTION
	19	The pfifo and bfifo qdiscs are unadorned First In, First Out queues. They are the
5699275b	20	simplest queues possible and therefore have no overhead.
09bba68c	21	.B pfifo
5699275b	22	constrains the queue size as measured in packets.
09bba68c SH	23	.B bfifo
	24	does so as measured in bytes.
	25
5699275b	26	Like all non-default qdiscs, they maintain statistics. This might be a reason to prefer
09bba68c SH	27	pfifo or bfifo over the default.
	28
	29	.SH ALGORITHM
	30	A list of packets is maintained, when a packet is enqueued it gets inserted at the tail of
5699275b	31	a list. When a packet needs to be sent out to the network, it is taken from the head of the list.
09bba68c SH	32
	33	If the list is too long, no further packets are allowed on. This is called 'tail drop'.
	34
	35	.SH PARAMETERS
5699275b	36	.TP
09bba68c	37	limit
5699275b SH	38	Maximum queue size. Specified in bytes for bfifo, in packets for pfifo. For pfifo, defaults
5699275b SH	39	to the interface txqueuelen, as specified with
09bba68c SH	40	.BR ifconfig (8)
	41	or
	42	.BR ip (8).
524de027	43	The range for this parameter is [0, UINT32_MAX].
09bba68c SH	44
09bba68c SH	45	For bfifo, it defaults to the txqueuelen multiplied by the interface MTU.
524de027 LW	46	The range for this parameter is [0, UINT32_MAX] bytes.
	47
	48	Note: The link layer header was considered when counting packets length.
09bba68c SH	49
09bba68c SH	50	.SH OUTPUT
5699275b	51	The output of
09bba68c	52	.B tc -s qdisc ls
5699275b SH	53	contains the limit, either in packets or in bytes, and the number of bytes
5699275b SH	54	and packets actually sent. An unsent and dropped packet only appears between braces
09bba68c SH	55	and is not counted as 'Sent'.
09bba68c SH	56
5699275b	57	In this example, the queue length is 100 packets, 45894 bytes were sent over 681 packets.
09bba68c SH	58	No packets were dropped, and as the pfifo queue does not slow down packets, there were also no
	59	overlimits:
	60	.P
	61	.nf
5699275b	62	# tc -s qdisc ls dev eth0
09bba68c	63	qdisc pfifo 8001: dev eth0 limit 100p
5699275b	64	Sent 45894 bytes 681 pkts (dropped 0, overlimits 0)
09bba68c SH	65	.fi
	66
	67	If a backlog occurs, this is displayed as well.
	68	.SH SEE ALSO
	69	.BR tc (8)
	70
	71	.SH AUTHORS
	72	Alexey N. Kuznetsov, <kuznet@ms2.inr.ac.ru>
	73
	74	This manpage maintained by bert hubert <ahu@ds9a.nl>