IronClad Rate Limiting
December 2000 14 - 13
Figure 14.6 shows an example of two Committed Time Intervals. In this example, the policy rule matches the
maximum number of conforming bytes (Normal Burst Size bytes) in each interval.
Figure 14.6 Excess Burst Size increments over every two Committed Time Intervals
The rule matches additional bytes in each interval, and thus applies the exceed action. The counter for the
Excess Burst Size increments over the span of the two intervals. Thus, the number of Excess Burst Size bytes
available for the second interval is the amount that remains after the first Committed Time Interval. In this
example, the rule matches 175,000,000 bits of additional (Excess Burst Size) data in the first Committed Time
Interval. The Excess Burst Size in the rule is set to 250,000,000 bits. As a result, only 75,000,000 Excess Burst
Size bits are available for use by the traffic that matches the rule in the second Committed Time Interval.
After the rule matches the maximum number of Normal Burst Size bytes in the second Committed Time Interval,
the rule matches an additional 75,000,000 bits. The software drops all bytes received in the second Committed
Time Interval after the Excess Burst Size maximum is reached.
Regardless of the actions for conforming and exceed traffic, the interface drops all traffic that matches a rule after
the rule has matched the maximum number bytes for the rule’s Normal Burst Size and Excess Burst Size.
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
Committed Time Interval = 1 second
bytes (750,000,000 bits)
Packets received
here are dropped.
One second
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.
Once maximum Excess Burst Size
is reached, traffic is dropped.
500,000,001 - 750,000,000
bits of packet data
175,000,000 bits received in
first Committed Time Interval
75,000,000 bits received in
second Committed Time
Interval
Additional packets received
in second Committed Time
interval are dropped.
Zero - 500,000,000
bits of packet data
500,000 received in
this Committed Time
Interval
Zero - 500,000,000
bits of packet data
500,000,000 received in
this Committed Time
Interval
One second
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