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Cisco 10000 Series Router Quality of Service Configuration Guide
OL-7433-09
Chapter 6 Policing Traffic
Metering Traffic and Token Buckets
Figure 6-1
Marking Packets and Assigning Actions—2-Rate Policer
For example, if a data stream with a rate of 250 kbps arrives at the two-rate policer, and the CIR is
100 kbps and the PIR is 200 kbps, the policer marks the packet in the following way:
•
100 kbps conforms to the rate
•
100 kbps exceeds the rate
•
50 kbps violates the rate
The router updates the tokens for both the committed and peak token buckets in the following way:
•
The router updates the committed token bucket at the CIR value each time a packet arrives at the
interface. The committed token bucket can contain up to the committed burst (bc) value.
•
The router updates the peak token bucket at the PIR value each time a packet arrives at the interface.
The peak token bucket can contain up to the peak burst (be) value.
•
When an arriving packet conforms to the CIR, the router takes the conform action on the packet and
decrements both the committed and peak token buckets by the number of bytes of the packet.
•
When an arriving packet exceeds the CIR, the router takes the exceed action on the packet,
decrements the committed token bucket by the number of bytes of the packet, and decrements the
peak token bucket by the number of overflow bytes of the packet.
•
When an arriving packet exceeds the PIR, the router takes the violate action on the packet, but does
not decrement the peak token bucket.
No
PIR
Be
Yes
Action
B > Tp
Packet of size B
Violate
No
Yes
Action
B > Tc
Exceed
Action
Conform
CIR
Bc
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