# man > tc-police(8)

_Policing_ _action_ _in_ [_tc_(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)                        Linux                       _Policing_ _action_ _in_ [_tc_(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)

## 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  algo‐
       rithm 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 un‐
              limited.

       **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 exceed‐
                     ing 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 ex‐
       ceeding 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  be‐
       tween  qdisc  and  action. The example above uses **u32 **for that, which is configured to effec‐
       tively match any packet (passing it to the **police **action thereby).


## SEE ALSO
       [**tc**(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)

iproute2                                     20 Jan 2015                    _Policing_ _action_ _in_ [_tc_(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)