Cisco Catalyst 4500 Series Command Reference Manual page 578

police (two rates)
Command History Release
12.2(40)SG
Usage Guidelines
Refer to RFC 2698-Two Rate Three Color Marker.
Two-rate traffic policing uses two token buckets—Tc and Tp—for policing traffic at two independent
rates. Note the following points about the two token buckets:
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Updating Token Buckets
The following scenario illustrates how the token buckets are updated:
A packet of B bytes arrives at time t. The last packet arrived at time t1. The CIR and the PIR token
buckets at time t are represented by Tc(t) and Tp(t), respectively. Using these values and in this scenario,
the token buckets are updated as follows:
Marking Traffic
The two-rate policer marks packets as either conforming, exceeding, or violating a specified rate. The
following points (using a packet of B bytes) illustrate how a packet is marked:
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Otherwise, the packet is marked as conforming to the specified rate, and both token buckets—Tc(t) and
Tp(t)—are updated as follows:
For example, if the CIR is 100 kbps, the PIR is 200 kbps, and a data stream with a rate of 250 kbps arrives
at the two-rate policer, the packet would be marked as follows:
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•
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Marking Packets and Assigning Actions Flowchart
The flowchart in
corresponding action (that is, violate, exceed, or conform) to the packet.
Catalyst 4500 Series Switch Cisco IOS Command Reference—Release IOS XE 3.4.0SG and IOS 15.1(2)SG)
2-520
Modification
This command was introduced on the Catalyst 4500 series switch using a Supervisor
Engine 6-E.
The Tc token bucket is updated at the CIR value each time a packet arrives at the two-rate policer.
The Tc token bucket can contain up to the confirm burst (Bc) value.
The Tp token bucket is updated at the PIR value each time a packet arrives at the two-rate policer.
The Tp token bucket can contain up to the peak burst (Be) value.
Tc(t) = min(CIR * (t-t1) + Tc(t1), Bc)
Tp(t) = min(PIR * (t-t1) + Tp(t1), Be)
If B > Tp(t), the packet is marked as violating the specified rate.
If B > Tc(t), the packet is marked as exceeding the specified rate, and the Tp(t) token bucket is
updated as Tp(t) = Tp(t) – B.
Tp(t) = Tp(t) – B
Tc(t) = Tc(t) – B
100 kbps would be marked as conforming to the rate.
100 kbps would be marked as exceeding the rate.
50 kbps would be marked as violating the rate.
Figure 2-1 illustrates how the two-rate policer marks packets and assigns a
Chapter 2 Cisco IOS Commands for the Catalyst 4500 Series Switches
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