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

.TH PIE 8 "16 January 2014" "iproute2" "Linux"
.SH NAME
PIE \- Proportional Integral controller-Enhanced AQM algorithm
.SH SYNOPSIS
.B tc qdisc ... pie
[
.B limit
PACKETS ] [
.B target
TIME ] [
.B tupdate
TIME ] [
.B alpha
int ] [
.B beta
int ] [
.B ecn
|
.B noecn
] [
.B bytemode
|
.B nobytemode
]

.SH DESCRIPTION
Proportional Integral controller-Enhanced (PIE) is a control theoretic active
queue management scheme. It is based on the proportional integral controller but
aims to control delay. The main design goals are
 o Low latency control
 o High link utilization
 o Simple implementation
 o Guaranteed stability and fast responsiveness

.SH ALGORITHM
PIE is designed to control delay effectively. First, an average dequeue rate is
estimated based on the standing queue. The rate is used to calculate the current
delay. Then, on a periodic basis, the delay is used to calculate the dropping
probabilty. Finally, on arrival, a packet is dropped (or marked) based on this
probability.

PIE makes adjustments to the probability based on the trend of the delay i.e.
whether it is going up or down.The delay converges quickly to the target value
specified.

alpha and beta are statically chosen parameters chosen to control the drop probability
growth and are determined through control theoretic approaches. alpha determines how
the deviation between the current and target latency changes probability. beta exerts
additional adjustments depending on the latency trend.

The drop probabilty is used to mark packets in ecn mode. However, as in RED,
beyond 10% packets are dropped based on this probability. The bytemode is used
to drop packets proportional to the packet size.

Additional details can be found in the paper cited below.

.SH PARAMETERS
.SS limit
limit on the queue size in packets. Incoming packets are dropped when this limit
is reached. Default is 1000 packets.

.SS target
is the expected queue delay. The default target delay is 20ms.

.SS tupdate
is the frequency at which the system drop probability is calculated. The default is 30ms.

.SS alpha
.SS beta
alpha and beta are parameters chosen to control the drop probability. These
should be in the range between 0 and 32.

.SS ecn | noecn
is used to mark packets instead of dropping
.B ecn
to turn on ecn mode,
.B noecn
to turn off ecn mode. By default,
.B ecn
is turned off.

.SS bytemode | nobytemode
is used to scale drop probability proportional to packet size
.B bytemode
to turn on bytemode,
.B nobytemode
to turn off bytemode. By default,
.B bytemode
is turned off.

.SH EXAMPLES
 # tc qdisc add dev eth0 root pie
 # tc -s qdisc show
   qdisc pie 8034: dev eth0 root refcnt 2 limit 200p target 19000us tupdate 29000us alpha 2 beta 20
   Sent 7443524 bytes 7204 pkt (dropped 900, overlimits 0 requeues 0)
   backlog 38998b 37p requeues 0
   prob 0.123384 delay 25000us avg_dq_rate 1464840
   pkts_in 7241 overlimit 900 dropped 0 maxq 186 ecn_mark 0

 # tc qdisc add dev eth0 root pie limit 100 target 20ms tupdate 30ms ecn
 # tc -s qdisc show
   qdisc pie 8036: dev eth0 root refcnt 2 limit 200p target 19000 tupdate 29000 alpha 2 beta 20 ecn
   Sent 2491922 bytes 2507 pkt (dropped 214, overlimits 0 requeues 0)
   backlog 33728b 32p requeues 0
   prob 0.102262 delay 24000us avg_dq_rate 1464840
   pkts_in 2468 overlimit 214 dropped 0 maxq 192 ecn_mark 71


 # tc qdisc add dev eth0 root pie limit 100 target 50ms tupdate 30ms bytemode
 # tc -s qdisc show
   qdisc pie 8036: dev eth0 root refcnt 2 limit 200p target 19000 tupdate 29000 alpha 2 beta 20 ecn
   Sent 2491922 bytes 2507 pkt (dropped 214, overlimits 0 requeues 0)
   backlog 33728b 32p requeues 0
   prob 0.102262 delay 24000us avg_dq_rate 1464840
   pkts_in 2468 overlimit 214 dropped 0 maxq 192 ecn_mark 71


.SH SEE ALSO
.BR tc (8),
.BR tc-codel (8)
.BR tc-red (8)

.SH SOURCES
 o IETF draft submission is at http://tools.ietf.org/html/draft-pan-tsvwg-pie-00
 o IEEE  Conference on High Performance Switching and Routing 2013 : "PIE: A
Lightweight Control Scheme to Address the Bufferbloat Problem"

.SH AUTHORS
PIE was implemented by Vijay Subramanian and Mythili Prabhu, also the authors of
this man page. Please report bugs and corrections to the Linux networking
development mailing list at <netdev@vger.kernel.org>.
Commit	Line	Data
8c452755 MP	1	.TH PIE 8 "16 January 2014" "iproute2" "Linux"
	2	.SH NAME
	3	PIE \- Proportional Integral controller-Enhanced AQM algorithm
	4	.SH SYNOPSIS
	5	.B tc qdisc ... pie
	6	[
	7	.B limit
	8	PACKETS ] [
	9	.B target
	10	TIME ] [
	11	.B tupdate
	12	TIME ] [
	13	.B alpha
	14	int ] [
	15	.B beta
	16	int ] [
	17	.B ecn
	18	\|
	19	.B noecn
	20	] [
	21	.B bytemode
	22	\|
	23	.B nobytemode
	24	]
	25
	26	.SH DESCRIPTION
	27	Proportional Integral controller-Enhanced (PIE) is a control theoretic active
	28	queue management scheme. It is based on the proportional integral controller but
	29	aims to control delay. The main design goals are
	30	o Low latency control
	31	o High link utilization
	32	o Simple implementation
	33	o Guaranteed stability and fast responsiveness
	34
	35	.SH ALGORITHM
	36	PIE is designed to control delay effectively. First, an average dequeue rate is
	37	estimated based on the standing queue. The rate is used to calculate the current
	38	delay. Then, on a periodic basis, the delay is used to calculate the dropping
	39	probabilty. Finally, on arrival, a packet is dropped (or marked) based on this
	40	probability.
	41
	42	PIE makes adjustments to the probability based on the trend of the delay i.e.
	43	whether it is going up or down.The delay converges quickly to the target value
	44	specified.
	45
	46	alpha and beta are statically chosen parameters chosen to control the drop probability
	47	growth and are determined through control theoretic approaches. alpha determines how
	48	the deviation between the current and target latency changes probability. beta exerts
	49	additional adjustments depending on the latency trend.
	50
	51	The drop probabilty is used to mark packets in ecn mode. However, as in RED,
a89d5329	52	beyond 10% packets are dropped based on this probability. The bytemode is used
8c452755 MP	53	to drop packets proportional to the packet size.
	54
	55	Additional details can be found in the paper cited below.
	56
	57	.SH PARAMETERS
	58	.SS limit
	59	limit on the queue size in packets. Incoming packets are dropped when this limit
	60	is reached. Default is 1000 packets.
	61
	62	.SS target
	63	is the expected queue delay. The default target delay is 20ms.
	64
	65	.SS tupdate
	66	is the frequency at which the system drop probability is calculated. The default is 30ms.
	67
	68	.SS alpha
	69	.SS beta
	70	alpha and beta are parameters chosen to control the drop probability. These
	71	should be in the range between 0 and 32.
	72
	73	.SS ecn \| noecn
	74	is used to mark packets instead of dropping
	75	.B ecn
	76	to turn on ecn mode,
	77	.B noecn
	78	to turn off ecn mode. By default,
	79	.B ecn
	80	is turned off.
	81
	82	.SS bytemode \| nobytemode
	83	is used to scale drop probability proportional to packet size
	84	.B bytemode
	85	to turn on bytemode,
	86	.B nobytemode
	87	to turn off bytemode. By default,
	88	.B bytemode
	89	is turned off.
	90
	91	.SH EXAMPLES
	92	# tc qdisc add dev eth0 root pie
	93	# tc -s qdisc show
	94	qdisc pie 8034: dev eth0 root refcnt 2 limit 200p target 19000us tupdate 29000us alpha 2 beta 20
	95	Sent 7443524 bytes 7204 pkt (dropped 900, overlimits 0 requeues 0)
	96	backlog 38998b 37p requeues 0
	97	prob 0.123384 delay 25000us avg_dq_rate 1464840
	98	pkts_in 7241 overlimit 900 dropped 0 maxq 186 ecn_mark 0
	99
	100	# tc qdisc add dev eth0 root pie limit 100 target 20ms tupdate 30ms ecn
	101	# tc -s qdisc show
	102	qdisc pie 8036: dev eth0 root refcnt 2 limit 200p target 19000 tupdate 29000 alpha 2 beta 20 ecn
	103	Sent 2491922 bytes 2507 pkt (dropped 214, overlimits 0 requeues 0)
	104	backlog 33728b 32p requeues 0
	105	prob 0.102262 delay 24000us avg_dq_rate 1464840
	106	pkts_in 2468 overlimit 214 dropped 0 maxq 192 ecn_mark 71
	107
	108
	109	# tc qdisc add dev eth0 root pie limit 100 target 50ms tupdate 30ms bytemode
	110	# tc -s qdisc show
	111	qdisc pie 8036: dev eth0 root refcnt 2 limit 200p target 19000 tupdate 29000 alpha 2 beta 20 ecn
	112	Sent 2491922 bytes 2507 pkt (dropped 214, overlimits 0 requeues 0)
	113	backlog 33728b 32p requeues 0
	114	prob 0.102262 delay 24000us avg_dq_rate 1464840
	115	pkts_in 2468 overlimit 214 dropped 0 maxq 192 ecn_mark 71
	116
117
118	.SH SEE ALSO
119	.BR tc (8),
120	.BR tc-codel (8)
121	.BR tc-red (8)
122
123	.SH SOURCES
124	o IETF draft submission is at http://tools.ietf.org/html/draft-pan-tsvwg-pie-00
125	o IEEE Conference on High Performance Switching and Routing 2013 : "PIE: A
126	Lightweight Control Scheme to Address the Bufferbloat Problem"
127
128	.SH AUTHORS
129	PIE was implemented by Vijay Subramanian and Mythili Prabhu, also the authors of
130	this man page. Please report bugs and corrections to the Linux networking
131	development mailing list at <netdev@vger.kernel.org>.