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NG_CAR(4)		 BSD Kernel Interfaces Manual		     NG_CAR(4)

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.  Commit‐
	     ted 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.  Com‐
	     mitted 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_SIN‐
	     GLE_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 pack‐
     ets.

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.

BSD				March 11, 2007				   BSD
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