Chapter 23
| Quality of Service Commands
– 654 –
violate-action - Action to take when rate exceeds the BE. (There are not
enough tokens in bucket BE to service the packet, the packet is set red.)
transmit - Transmits without taking any action.
drop - Drops packet as required by exceed-action or violate-action.
new-dscp - Differentiated Service Code Point (DSCP) value. (Range: 0-63)
Default Setting
None
Command Mode
Policy Map Class Configuration
Command Usage
â—† You can configure up to 16 policers (i.e., class maps) for ingress ports.
â—† The
committed-rate
cannot exceed the configured interface speed, and the
committed-burst
and excess-burst cannot exceed 16 Mbytes.
â—† The srTCM as defined in RFC 2697 meters a traffic stream and processes its
packets according to three traffic parameters – Committed Information Rate
(CIR), Committed Burst Size (BC), and Excess Burst Size (BE).
â—† The PHB label is composed of five bits, three bits for per-hop behavior, and two
bits for the color scheme used to control queue congestion. A packet is marked
green if it doesn't exceed the CIR and BC, yellow if it does exceed the CIR and
BC, but not the BE, and red otherwise.
â—† The meter operates in one of two modes. In the color-blind mode, the meter
assumes that the packet stream is uncolored. In color-aware mode the meter
assumes that some preceding entity has pre-colored the incoming packet
stream so that each packet is either green, yellow, or red. The marker (re)colors
an IP packet according to the results of the meter. The color is coded in the DS
field [RFC 2474] of the packet.
â—† The behavior of the meter is specified in terms of its mode and two token
buckets, C and E, which both share the common rate CIR. The maximum size of
the token bucket C is BC and the maximum size of the token bucket E is BE.
The token buckets C and E are initially full, that is, the token count Tc(0) = BC
and the token count Te(0) = BE. Thereafter, the token counts Tc and Te are
updated CIR times per second as follows:
â–
If Tc is less than BC, Tc is incremented by one, else
â–
if Te is less then BE, Te is incremented by one, else
â–
neither Tc nor Te is incremented.
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