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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.

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 (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.