UMN:CLI
User Manual
V8102
340
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Peak Information Rate (PIR)
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Committed Burst Size (CBS)
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Excess Burst Size (EBS)
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Peak Burst Size (PBS)
A typical meter measures the rate at which traffic stream passes it. Its rate estimation de-
pends upon the flow state kept by the meter. There is a time constraint during which if the
flow state is transferred from the old switch to the new switch, then it is effective in esti-
mating the rate at the new switch as if though no transfer of flow has happened.
The V8102 provides Token Bucket (srTCM and trTCM) meters.
Token Bucket
The token bucket is a control mechanism that transmits traffic by tokens in the bucket.
The tokens are consumed by transmitting traffic and regenerated at the given rate. If all
tokens in the bucket are consumed out, traffic cannot be transmitted any more; a flow can
transmit traffic up to its peak burst rate. The transmitting cost and regenerating rate of to-
kens are configurable.
Token
Packet
Packet consumes
tokens in the bucket
Forwarding
Tokens are regenerated
at a given rate (CIR, PIR)
CBS
EBS
PBS
Token
Fig. 9.7
Token Bucket Meter
Single Rate Three Color Marker (srTCM)
The srTCM meters an IP packet stream and marks its packet the one among green, yel-
low, and red using Committed Information Rate (CIR) and two associated burst sizes,
Committed Burst Size (CBS) and Excess Burst Size (EBS). A packet is marked green if it
does not exceed the CBS, yellow if it exceeds the CBS, but not the EBS, and red other-
wise. The srTCM is useful for ingress policing of a service, where only the length, not the
peak rate, of the burst determines service eligibility.
