Unanswered Question
Jul 22nd, 2008


i am having CCM 4.1 and unity 4.0.i want to know that what is the minium number of voice mail port that i must configure and what is the number of maxium voice mail port that i can configure?i know that how to transfer a single phone directly to voice mail and i also know that how to transfer all the phone to voice mail but i want to know that suppose i am having 100 phones(7902 and 7940)in my network.i want to transfer half of the phone directly to voice mail and in the remaining phones after a certain ring duration it will go to voice mail.i want to do this in bulk not by a single single phone.

If anyone having that solution please help me.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
thfergus Tue, 07/22/2008 - 06:33

The following was extracted from a Cisco Press book entitled Cisco IP Telephony:

Planning, designm Implementation, Operation and Optimazation:

Sizing Unity Ports and Sessions

The number of Unity ports in a system determines the number of simultaneous callers who

can call into the Unity system. Because ports or sessions are licensed components in

Unity, XYZ has to pay a license for each. Therefore, proper sizing of the Unity

ports/session is important to avoid paying for unneeded ports/sessions.

There are two different approaches to doing port sizing. The first approach, adopted by

XYZ, is to use a port-to-user ratio of 1:20 to determine the number of ports or sessions

required on the Octel voice-mail system. Using the same approach, for 550 users (including

the users at Melbourne and Brisbane), 28 ports are needed on the Unity server. In Unity,

you also need a few ports exclusively reserved for lighting the MWI on the handsets of IP

Phones and a few ports exclusively reserved for Outcall notification purposes. Therefore,

after reserving two ports each for these purposes, XYZ requires a Unity system with 32


In the second approach to port sizing the Unity system, the number of ports required

depends on the following parameters:

Average calls per hour to the voice-mail system

Average length in seconds

If you have an existing voice-mail system, these parameters are available in the system

reports. After you have these parameters, to calculate the number of ports required, use

the following formula:

Number of ports or sessions= Average calls per hour / average lenght in hours.

As an example, assume that a customer has on average 200 calls per hour into the system

with an average length of 4 minutes (240 seconds) for voice-mail messages. Based on this

information, this customer requires a Unity system with 13 ports. Taking into

consideration the additional ports that must be reserved for MWI and Outcall notifications

and future expansion possibilities, the customer could deploy one primary Unity server

with 20 ports and one standby Unity server with 20 ports for failover situations.

Authors are Ramesh Kaza and Salman Asadullah and ISBN numbers are

Print ISBN-10: 1-58705-157-5

Print ISBN-13: 978-1-58705-157-9

Tommer Catlin Tue, 07/22/2008 - 14:44

If you have 100 phones on your network and forward all calls to voicemail (50 lines). The next question would be, how many incoming lines do you have? If you only have 24 channels from PRI (23..) you may be at your limit to a 1:2 port ratio.

Call Centers who are cheap will try that ratio. A good call center will have a 1:1 Channel to agent ratio. Gauging voicemail is a little tricky. If you have Voicemail Only, you will have more people using the TUI or dialing into Unity and hogging the ports just checking messages.

If you have Unified Messaging, less people will use the TUI and more will use their email client to listen to messages. (do not require a port to listen to messages) So the port count goes down.

If you have a slew of Call Handlers on your system, your port count will go up. I had customer who need a single Unity server just for CallHandlers... (get the idea)

Basically, if you have 100 phones... start with 16 ports. If you need more, you can always order more ports for your server. You can run weekly reports to see your port utilization by the hour/day/etc. If you plan on going from 100 to 2000 phones, then the actual server could change to handle the amount ports you would need to support.

But typically, 16 ports in UM environment with 100 phones a small amount of call handler traffic is plenty. Most customers who go from a 32 port legacy system voicemail to Unity to UM will actually drop down to 16 or 24 ports because they will not even come close using all 32 ports at any given one time.

hope this helps


This Discussion