[Asterisk-Users] Traffic Modelling (was IVR only system with scalibility...)

[George Pajari]

The question was posed:

"incomming calls for 45 or so people that will call in 3 or 4 time each 
day during (approx) normal business hours"

The comment was made (taken out of context):

"The quick math says that 45 people with 4 calls is 180 calls a
day. In a 8 hour day you have 480 minutes. From 480 minutes 1 port could
handle the load if the call was under 2.5 minutes long and everyone
waited till it became available."

Unfortunately as we all know, asking callers to guess when the line is 
free and equally spacing their calls is not terribly realistic (as the 
author of the comment above goes on to imply).

So how does one analyse such a situation? Using statistical traffic 
modelling!

For more information, see http://www.erlang.com/calculator/erlb/

Plug in:
	Busy Hour Traffic: 0.937 Erlangs
	(based on 45 * 4 * 2.5 / 480)

	Acceptable Blocking Factor: 1%
	(we will accept 1 in 100 calls receiving a busy signal)

Result:
	you will need 5 incoming lines.

If you are willing to tolerate (say) 3% of calls receiving a busy 
signal, you can get by with 4 lines etc. and etc.

Hope you find the above useful in planning your Asterisk installation.