Unity Port Sizing

[johutchins]

Hi all,

I have a client that is concerned that 16 ports will not be enough for his 60 user (to be 300 in 3 years) Unity VMO server. It is going to be installed on a MCS 7825 which maxes out at 16 ports.

I did some searching, but I'm not coming up with any good guidelines or anything and I want to give him a better answer than "Trust me".

Thanks.

--Jon

[johutchins]

I think I got it... I dug out a Cisco book and found some calcs using AHT and an Erlang B calculator. I made some assumptions like 30% of users would have new messages and on average it would take 3 minutes to get the message.

Are there any better stats out there for VM specifically?

--Jon

[mdeloach]

I cannot direct you to better stats, but I can offer one observation from our deployment.

We were thinking much the same, that 16 ports would be constraining as we grew. We forgot to factor in the idea that users would quickly get used to listening to their messages through Outlook. We opted for the 32 port license in our ~200 employee office, and the high watermark for ports in use is around five.

[johutchins]

Well, one of the guys on staff scared everyone by saying his last company of 100 people used 32 ports and they still got busy signals.

I work for a reseller and have never had to do a port upgrade, but I've never really been asked to justify port count.

I'm pretty happy with the Erlang B calculation, but I made assumptions. I guess it depends on how that company uses voicemail.

Also, for this install, they are Voice Mail Only, but they may upgrade to UM someday... Perhaps instead of adding more ports.

--Jon

[cfortanb]

One thing alot of customers forget to factor in is the use of auto attendant. My guess is the 32ports/100 users used AA to route their calls. I had a customer that had 25 users, and 40 ports, and it wasn't enough. They used AA to route callers to order takers that didn't have VM boxes. Really depends on HOW they use VM.