Vik,

We have used pipelimit at a sampling interval of 1 second, and, on the basis of contact with reality, decided to shift to a 3-second sampling window.

The major problem with the 1-second interval is not the CPU usage, but that it's not very useful. Such a sampling window is extremely responsive to fluctuations within a short time, and this manifests very well in SIPP testing.

However, SIPP generates calls in an orderly and linear fashion. Real-world SIP traffic is highly bursty and volatile. The result is that a 1-second sampling window will not properly encapsulate the data so as to reliably enforce a CPS limit of X. For example, if you set a limit of 300 CPS, the short sampling window makes it quite possible to burst far beyond 300 CPS as long as it is done within < 50% of the duty cycle.

3 seconds is a more realistic compromise. In virtue of smoothing some peaks, it is less dynamic and responsive, but it far more accurately takes into account the bursty and chaotic nature of real-world high-volume call setups. These are not modeled well with SIPP testing.

-- Alex


--
Alex Balashov | Principal | Evariste Systems LLC
303 Perimeter Center North, Suite 300
Atlanta, GA 30346
United States

Tel: +1-800-250-5920 (toll-free) / +1-678-954-0671 (direct)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/

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