8 Port Estimator

The Port Estimator tool allows you to estimate the number of telephony ports you're deployed application will require. This tool uses an Erlang B queueing model (M/M/k/1) to estimate the number of ports needed to support a given quality of service.

The Erlang B model assumes:

•	The Call Arrival Rate is Poisson distributed.
•	The Service Rate (Average Call Duration) is exponentially distributed.
•	The Number of Callers is much larger than the number of ports.
•	When a caller finds all ports in use (busy signal), the caller hangs up and does not redial. (There is no queue).

Note: To use the BeVocal tools, you must have the Java Runtime Environment (JRE) 1.5.7 installed on your computer.

Estimating Port Capacity

1.	Click Port Estimator on the Tools & File Management menu to bring up the Port Estimator window. The command portion of this window initially appears as follows:

2.	Enter your expected Call Arrival Rate and Average Call Duration. You can also enter a number of ports.
3.	Click Recalculate.
	The Busy signals line updates to indicate what percentage of callers will encounter a busy signal with these parameters. In addition, the table below the command portion updates to show the percentage of callers that would encounter busy signals for varying numbers of ports given that same call arrival rate and average call duration.

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