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NG_CAR(4)		     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.  Committed
	     burst packets are counted as  green,  extended  burst  packets  are
	     counted  as  yellow and exceeding packets are counted as red.  Com-
	     mitted 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 ex-
	     tended  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.   Pack-
	     ets  dropped  by  queue counted as red.  Queue parameters are hard-
	     coded: 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.

CONTROL MESSAGES
     This node type supports the generic control messages and the following spe-
     cific 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 (bytes) */
		     u_int64_t ebs;	     /* Exceeded/Peak burst size (bytes) */
		     u_int64_t cir;	     /* Committed information rate (bits/s) */
		     u_int64_t pir;	     /* Peak information rate (bits/s) */
		     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;	     /* single/double rate, ... */
		     u_int8_t opt;	     /* color-aware or color-blind */
	     };

	     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.

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.

FreeBSD 7.0			 March 11, 2007 		       NG_CAR(4)
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