tc-police(8) - man - phpMan

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  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)



iproute2                                     20 Jan 2015                    Policing action in tc(8)