Policing action in tc(8)             Linux            Policing action in tc(8)



NAME
       police - policing action

SYNOPSIS
       tc ... action police [ rate RATE burst BYTES[/BYTES] ] [ pkts_rate RATE
               pkts_burst PACKETS] [ mtu BYTES[/BYTES] ] [ peakrate RATE ] [
               overhead BYTES ] [ linklayer TYPE ] [ CONTROL ]

       tc ... filter ... [ estimator SAMPLE AVERAGE ] action police avrate
               RATE [ CONTROL ]

       CONTROL := conform-exceed EXCEEDACT[/NOTEXCEEDACT

       EXCEEDACT/NOTEXCEEDACT := {  pipe | ok | reclassify | drop | continue |
               goto chain CHAIN_INDEX }

DESCRIPTION
       The police action allows limiting of the byte or packet rate of traffic
       matched by the filter it is attached to.

       There are two different algorithms available to measure the byte rate:
       The first one uses an internal dual token bucket and is configured
       using the rate, burst, mtu, peakrate, overhead and linklayer
       parameters. The second one uses an in-kernel sampling mechanism. It can
       be fine-tuned using the estimator filter parameter.

       There is one algorithm available to measure packet rate and it is
       similar to the first algorithm described for byte rate. It is
       configured using the pkt_rate and pkt_burst parameters.

       At least one of the rate and pkt_rate parameters must be configured.

OPTIONS
       rate RATE
              The maximum byte rate of packets passing this action. Those
              exceeding it will be treated as defined by the conform-exceed
              option.

       burst BYTES[/BYTES]
              Set the maximum allowed burst in bytes, optionally followed by a
              slash ('/') sign and cell size which must be a power of 2.

       pkt_rate RATE
              The maximum packet rate or packets passing this action. Those
              exceeding it will be treated as defined by the conform-exceed
              option.

       pkt_burst PACKETS
              Set the maximum allowed burst in packets.

       mtu BYTES[/BYTES]
              This is the maximum packet size handled by the policer (larger
              ones will be handled like they exceeded the configured rate).
              Setting this value correctly will improve the scheduler's
              precision.  Value formatting is identical to burst above.
              Defaults to unlimited.

       peakrate RATE
              Set the maximum bucket depletion rate, exceeding rate.

       avrate RATE
              Make use of an in-kernel bandwidth rate estimator and match the
              given RATE against it.

       overhead BYTES
              Account for protocol overhead of encapsulating output devices
              when computing rate and peakrate.

       linklayer TYPE
              Specify the link layer type.  TYPE may be one of ethernet (the
              default), atm or adsl (which are synonyms). It is used to align
              the precomputed rate tables to ATM cell sizes, for ethernet no
              action is taken.

       estimator SAMPLE AVERAGE
              Fine-tune the in-kernel packet rate estimator.  SAMPLE and
              AVERAGE are time values and control the frequency in which
              samples are taken and over what timespan an average is built.

       conform-exceed EXCEEDACT[/NOTEXCEEDACT]
              Define how to handle packets which exceed or conform the
              configured bandwidth limit. Possible values are:

              continue
                     Don't do anything, just continue with the next action in
                     line.

              drop   Drop the packet immediately.

              shot   This is a synonym to drop.

              ok     Accept the packet. This is the default for conforming
                     packets.

              pass   This is a synonym to ok.

              reclassify
                     Treat the packet as non-matching to the filter this
                     action is attached to and continue with the next filter
                     in line (if any). This is the default for exceeding
                     packets.

              pipe   Pass the packet to the next action in line.

EXAMPLES
       A typical application of the police action is to enforce ingress
       traffic rate by dropping exceeding packets. Although better done on the
       sender's side, especially in scenarios with lack of peer control (e.g.
       with dial-up providers) this is often the best one can do in order to
       keep latencies low under high load. The following establishes input
       bandwidth policing to 1mbit/s using the ingress qdisc and u32 filter:

              # tc qdisc add dev eth0 handle ffff: ingress
              # tc filter add dev eth0 parent ffff: u32 \
                   match u32 0 0 \
                   police rate 1mbit burst 100k

       As an action can not live on it's own, there always has to be a filter
       involved as link between qdisc and action. The example above uses u32
       for that, which is configured to effectively match any packet (passing
       it to the police action thereby).


SEE ALSO
       tc(8)

iproute2                          20 Jan 2015         Policing action in tc(8)