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System Management Console User Guide
Standard
• BucketCapacityFactor—used to determine the size of the token bucket
(BucketCapacityFactor
× MaxAttemptsPerInterval = bucket size)
— range: 1-MAXINT
— Session Manager default: 165
— other network element default: 1
• MaxNumSuspects—the maximum number of source IP addresses that can be
monitored at one time
— range: 1-MAXINT
— default: 1000
Calculations
Use the following calculations to determine the SIP DoS parameter values.
Sustained Rate = SIPTrans_MaxAttemptsPerInterval / SIPTrans_SampleInterval
BucketSize = num_attempts_per_interval
× SIPTrans_BucketCapcityFactor
BucketSize = BurstLength (BurstRate – SustainedRate)
SIPTrans_BucketCapcityFactor = 2160 / 20 = 108
Time to fill bucket = 2160 tokens / (4 tokens/s) = 540s
Example using the default values
Using the operating parameters, and assuming a 50 ms round trip delay, the
following calculations can be made.
Sustained Rate = 20 / 5 = 4 trans/s
BurstRate = 1/50ms
× 1000ms/s × 5 threads = 100 trans/s
BurstLength = 1s/100 trans
× 750 × 3 = 22.5s (amount of time needed to send 750
subscribe messages 3 times)
BucketSize = 22.5 (100 – 4) = 2160 tokens