tc-police

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

NAME
       police - policing action

SYNOPSIS
       tc  ... action police rate RATE burst BYTES[/BYTES] [ 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 to limit bandwidth of traffic matched by the
       filter it is attached to. Basically there are two different  algorithms
       available  to  measure  the packet 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.

OPTIONS
       rate RATE
              The  maximum  traffic 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.

       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 preci-
              sion.  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 AVER-
              AGE 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 config-
              ured 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 pack-
                     ets.

              pipe   Pass the packet to the next action in line.

EXAMPLES
       A  typical application of the police action is to enforce ingress traf-
       fic 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)
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