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CLI
182
Tokens are regenerated
based on CIR
CBS
Fig. 7.6
Bahavior of srTCM (3)
Two Rate Three Color Marker (trTCM)
The trTCM meters an IP packet stream and marks its packet the one among green, yel-
low, and red using Peak Information Rate (PIR) and its associated Peak Burst Size (PBS)
and Committed Information Rate (CIR) and its associated Committed Burst Size (CBS). A
packet is marked red if it exceeds the PIR. Otherwise, it is marked either yellow or green
depending on whether it exceeds or does not exceed CIR. The trTCM is useful for ingress
policing of a service, where a peak rate needs to be enforced separately from a commit-
ted rate.
PIR and CIR are the regenerating rate of tokens for PBS and CBS respectively, which is
measured in bytes of IP packets per second. PIR must be equal to or greater than CIR.
PBS and CBS are the maximum size for each token bucket, P and C, measured in bytes.
Both of them must be configured with the values equal to or greater than the size of the
largest possible IP packet in the stream.
The token buckets P and C are initially full. When a packet arrives, if the tokens in the
bucket P are smaller than the size of that packet, the packet is marked red. Else, if the to-
kens in the bucket C are smaller than the size of that packet, those are decremented by
the size of that packet with the yellow color-marking. Else, if the tokens in the bucket C
are larger than the size of that packet, those of both bucket P and C are decremented by
the size of that packet with the green color-marking.
Note that in the trTCM algorithm, when a packet arrives, the availability of tokens in the
token bucket P is checked first contrary to the srTCM; the order of color-marking is red-
yellow-green.
Bucket C
Empty
Packet
Management Guide
Tokens are regenerated
based on CIR
Bucket E
Empty
EBS
If both buckets are empty,
a packet is marked red
Red Color-Marking
TigerAccess™ EE
SMC7824M/VSW
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