How about a traffic study of the VTO ports from the switch side?
A) Capture the SMDR (CDR) records for the VTO extensions on the PBX and import them to some kind of database. Excel might even be enough. Apply some logic that looks at start times of the calls, the duration (or end time, depending upon the PBX you have,) and calculates concurency.
B) Another way to look at it would be to use those same records, broken out by hour. Add up the usage of all the ports for the hour, convert to CCS (hundredcallseconds: 100 seconds = 1 CCS) ((minutes * 60)/100 = CCS). Next, compare that to the available CCS for VTO. I think you said 60 ports. So, 60 * 36 [number of CSS in an hour]= 2160 CCS/hour capacity.
Using data from say an entire week (extend it to a year and you can find: Busy Day, Week, Hour, etc.) you can see what your busy hours each day are, and the busy hour for the week is. Design to that number and add some growth factor to get your minimum ports required for the traffic you are experiencing.
C) Take it a step further and apply a staffing calculator to the numbers (think of the VTO ports as Agents) and set the blocking factor to what makes sense, probably leave it at 01 grade of service, but you could make it 0.0 and see what happens (at 0.0 no calls would have the potential to be blocked)
Hope that helps.
Randy
