Unforeseen VoIP glitches range from who gets the fancy phones to how you track phone use by department so you can bill them for what they use.

The phone project manager should have veto power over who requires more than a standard handset, or department heads will start dishing out the more expensive, feature-rich models to people who really don't need them. "They want the phones with more buttons," says Roger Fahnestock, IT director for Kane County government in Illinois.

IP call servers log calls, but don't translate them into calls by department or flag the calls that cross the public phone network and incur toll charges. Customers should plan to buy software that converts the logs into readable bills if they hope to charge departments.

Businesses need to figure out how costs will be divided for VoIP, because it raises all sorts of questions. If a department gets one more employee, does it pay for the phone? If all the ports on that department's switch are full, who pays for another switch? If the IT department pays, what is a good way to plan for such unexpected costs?

Businesses must figure out how long they want the phones to work when the power fails. A one-unit battery backup may support a group of phones for 20 minutes, but it may require extended-run battery modules to keep phones up for three hours. That means planning for the cost of the backups and also figuring out whether there's enough space in the wiring closet to house them. In some cases, a back-up generator may be a better option.

Vendors have 999 schemes that link corporate IP phones to physical locations so ambulances can find the person who made a call for help, but these systems must interface with carrier 999 networks. Expect to dedicate time to make that interface work properly, because it is far from standard.

Departments left to set up their own interactive voice-response systems may come back to IT for help because they don't have a good sense of how to set them up. For example, one user cited a department that created 10 options for callers to choose, forced them to listen to all 10 before they could punch a number, and had no option to bump out to an operator. As a result, everybody was hanging up in frustration before they made a selection. Then the department head complained that the phones weren't working because there were no inbound calls.

If VoIP is intended to minimise the number of phone lines, businesses should plan to install a fax server to get rid of analogue fax lines. And if modems are necessary, plan to keep analogue lines to support them or be prepared to suffer with temperamental analogue-to-digital modem-conversion gear.

Preparing for VoIP

  • Set up two VoIP teams, one for network issues and one for customer issues, to keep responses sharp to both needs.
  • Plan air conditioning for wiring closets if using power over Ethernet switches - they generate more heat.
  • Remember that Gigabit Ethernet requires phones that support it or separate switch ports just for the phones.