[SR-Users] using pipelimit at CPS (1 second)

[Alex Balashov]

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

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