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NG_CAR(4)              FreeBSD Kernel Interfaces Manual              NG_CAR(4)

NAME
     ng_car - Committed Access Rate netgraph node type

SYNOPSIS
     #include <netgraph/ng_car.h>

DESCRIPTION
     The car node type limits traffic flowing through it using:

     +o   Single rate three color marker as described in RFC 2697,
     +o   Two rate three color marker as described in RFC 2698,
     +o   RED-like rate limit algorithm used by Cisco,
     +o   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 {
                  uint64_t cbs;           /* Commited burst size (bytes) */
                  uint64_t ebs;           /* Exceeded/Peak burst size (bytes) */
                  uint64_t cir;           /* Commited information rate (bits/s) */
                  uint64_t pir;           /* Peak information rate (bits/s) */
                  uint8_t  green_action;  /* Action for green packets */
                  uint8_t  yellow_action; /* Action for yellow packets */
                  uint8_t  red_action;    /* Action for red packets */
                  uint8_t  mode;          /* single/double rate, ... */
                  uint8_t  opt;           /* color-aware or color-blind */
          };

          /* 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 {
                  uint64_t passed_pkts;   /* Counter for passed packets */
                  uint64_t droped_pkts;   /* Counter for droped packets */
                  uint64_t green_pkts;    /* Counter for green packets */
                  uint64_t yellow_pkts;   /* Counter for yellow packets */
                  uint64_t red_pkts;      /* Counter for red packets */
                  uint64_t errors;        /* Counter for operation 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.

FreeBSD 11.0-PRERELEASE        November 13, 2012       FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | HOOKS | MODES OF OPERATION | CONTROL MESSAGES | SHUTDOWN | EXAMPLES | SEE ALSO | AUTHORS | BUGS

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