NAME¶
ng_car —
Commited Access Rate netgraph
node type
SYNOPSIS¶
#include <netgraph/ng_car.h>
DESCRIPTION¶
The
car node type limits traffic flowing through it using:
- Single rate three color
marker as described in RFC 2697,
- Two rate three color marker
as described in RFC 2698,
- RED-like rate limit
algorithm used by Cisco,
- Traffic shaping with
RED.
HOOKS¶
This node type supports the following hooks:
- upper
- Hook leading to upper layer protocols.
- lower
- Hook leading to lower layer protocols.
Traffic flowing from
upper to
lower
is considered
downstream traffic. Traffic flowing from
lower to
upper is considered
upstream traffic.
MODES OF OPERATION¶
Each hook can operate in one of the following modes:
NG_CAR_SINGLE_RATE
- Single rate three color marker as described in RFC 2697.
Committed burst packets are counted as green, extended burst packets are
counted as yellow and exceeding packets are counted as red. Committed
burst getting refilled with CIR (Committed Information Rate) speed. When
it is full, exceeded burst getting refilled.
NG_CAR_DOUBLE_RATE
- Two rate three color marker as described in RFC 2698.
Committed burst packets are counted as green, peak burst packets are
counted as yellow and exceeding packets are counted as red. Committed
burst getting refilled with CIR speed. Peak burst getting refilled with
PIR (Peak Information Rate) speed at the same time.
NG_CAR_RED
- Similar to
NG_CAR_SINGLE_RATE
, but
with different understanding of extended burst. When normal burst exceeded
and extended burst is used, packets are counted red with probability equal
to part of extended burst consumed. Extended burst getting refilled first.
When it is full, committed burst getting refilled. This behavior is
similar to RED active queue management algorithm.
This algorithm is more polite to the TCP traffic than
NG_CAR_SINGLE_RATE.
NG_CAR_SHAPE
- Committed burst packets are counted as green, exceeding
packets are delayed by queue with RED management and counted as yellow.
Packets dropped by queue counted as red. Queue parameters are hardcoded:
length 99 packets, min_th 8 packets, max_p 100%.
Traffic shaping is much more polite to the TCP traffic than rate limit on
links with bandwidth * delay product less than 6-8 TCP segments, but it
consumes additional system resources for queue processing.
By default, all information rates are measured in bits per second and bursts are
measured in bytes. But when NG_CAR_COUNT_PACKETS option is enabled, rates are
measured in packets per second and bursts are in packets.
CONTROL MESSAGES¶
This node type supports the generic control messages and the following specific
messages.
NGM_CAR_SET_CONF
(setconf
)
- Set node configuration to the specified at
struct ng_car_bulkconf
NGM_CAR_GET_CONF
(getconf
)
- Return current node configuration as struct
ng_car_bulkconf
struct ng_car_hookconf {
u_int64_t cbs; /* Committed burst size */
u_int64_t ebs; /* Exceeded/Peak burst size */
u_int64_t cir; /* Committed information rate */
u_int64_t pir; /* Peak information rate */
u_int8_t green_action; /* Action for green packets */
u_int8_t yellow_action; /* Action for yellow packets */
u_int8_t red_action; /* Action for red packets */
u_int8_t mode; /* operation mode */
u_int8_t opt; /* mode options */
};
/* possible actions (..._action) */
enum {
NG_CAR_ACTION_FORWARD = 1,
NG_CAR_ACTION_DROP
};
/* operation modes (mode) */
enum {
NG_CAR_SINGLE_RATE = 0,
NG_CAR_DOUBLE_RATE,
NG_CAR_RED,
NG_CAR_SHAPE
};
/* mode options (opt) */
#define NG_CAR_COUNT_PACKETS 2
struct ng_car_bulkconf {
struct ng_car_hookconf upstream;
struct ng_car_hookconf downstream;
};
NGM_CAR_GET_STATS
(getstats
)
- Return node statistics as struct
ng_car_bulkstats
struct ng_car_hookstats {
u_int64_t passed_pkts;
u_int64_t droped_pkts;
u_int64_t green_pkts;
u_int64_t yellow_pkts;
u_int64_t red_pkts;
u_int64_t errors;
};
struct ng_car_bulkstats {
struct ng_car_hookstats upstream;
struct ng_car_hookstats downstream;
};
NGM_CAR_CLR_STATS
(clrstats
)
- Clear node statistics.
NGM_CAR_GETCLR_STATS
(getclrstats
)
- Atomically return and clear node statistics.
SHUTDOWN¶
This node shuts down upon receipt of a
NGM_SHUTDOWN
control message, or when all hooks have been disconnected.
EXAMPLES¶
Limit outgoing data rate over fxp0 Ethernet interface to 20Mbit/s and incoming
packet rate to 5000pps.
/usr/sbin/ngctl -f- <<-SEQ
mkpeer fxp0: car lower lower
name fxp0:lower fxp0_car
connect fxp0: fxp0_car: upper upper
msg fxp0_car: setconf { downstream={ cir=20000000 cbs=2500000 ebs=2500000 greenAction=1 yellowAction=1 redAction=2 mode=2 } upstream={ cir=5000 cbs=100 ebs=100 greenAction=1 yellowAction=1 redAction=2 mode=2 opt=2 } }
SEQ
SEE ALSO¶
netgraph(4),
ngctl(8)
J. Heinanen, A
Single Rate Three Color Marker, RFC
2697.
J. Heinanen, A Two
Rate Three Color Marker, RFC 2698.
AUTHORS¶
Nuno Antunes ⟨nuno.antunes@gmail.com⟩
Alexander Motin ⟨mav@FreeBSD.org⟩
BUGS¶
At this moment only DROP and FORWARD actions are implemented.