полицейские действия (policing action)
Имя (Name)
police - policing action
Синопсис (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 }
Описание (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.
Параметры (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.
Примеры (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).
Смотри также (See also)
tc(8)
