[SR-Users] using pipelimit at CPS (1 second)
abalashov at evaristesys.com
Thu Jan 7 18:22:59 CET 2016
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
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 Balashov | Principal | Evariste Systems LLC
303 Perimeter Center North, Suite 300
Atlanta, GA 30346
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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