Rate Limiting
Figure 4.5 shows an example of the Normal Burst Size and Excess Burst Size counters. This example shows two Committed Time Intervals.
1000Mbps port
Excess Burst packets - received after maximum number of Normal Burst packets are received within the Committed Time Interval. The Exceed action applies to these packets.
Excess Burst Counter restarts at zero at the beginning of every second Committed Time Interval.
Normal Burst packets - The Conform action applies to these packets.
Normal Burst Counter restarts at zero at
the beginning of each Committed Time Interval.
Line rate = 1,000,000,000 bps (one Gigabit)
Average Rate = 500,000,000 bits
Normal Burst Size = 62,500,000 bytes (500,000,000 bits)
Excess Burst Size = 93,750,000 bytes (750,000,000 bits)
Committed Time Interval = 1 second
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| Zero - 500,000,000 |
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Figure 4.5 Normal and Excess Burst Size Counters
Notice that the counter for the Normal Burst Size counter restarts at the beginning of each Committed Time Interval, whereas the counter for the Excess Burst Size restarts after every two Committed Time Intervals. In this example, the policy rule on the interface matches 300,000,000 bits of Ethernet traffic data during the first Committed Time Interval. Therefore, all the traffic conformed to the policy rule and the software took the action specified for conforming traffic.
During the second Committed Time Interval, the policy rule on the interface matches 675,000,000 bits of Ethernet traffic data. Since the Normal Burst Size is 500,000,000, the software takes the conforming action for the first 500,000,000 bits. However, the software takes the exceed action for the remaining traffic. In this example, the action for conforming traffic is to set the IP precedence to 5, then forward the traffic. The action for exceed traffic is to set the IP precedence to 0, then forward the traffic.
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