IT managers involved in VoIP efforts said they face a daunting task: making sure that voice packets, which must be given priority on networks for reasons of sound quality, do not overload their data feeds.
"You've got to beef up the one network that's going to handle both voice and data," said Mark Katsourous, communication automation specialist at the University of Maryland in College Park.
The university has installed VoIP phones made by Avaya in some of its dormitories and remote locations. But to do a wider roll out, Katsourous said, he would first need to install new routers that could guarantee voice quality and backup power for the voice devices.
"There is no such thing as a quick voice over IP implementation," said Zeus Kerravala, an analyst at the Yankee Group. He said one of the chief limiting factors is that a wide-area network using a T3 carrier line "is only half the speed of a typical LAN", which is the bandwidth VoIP requires.
St Michael's Hospital in Toronto recently boosted bandwidth from 3mbps to 40mbps on its LAN and 20mbps on its WAN. "I wouldn't have entertained voice over IP on our previous network," said chief information officer, John Wegener.
Like other users, St Michael's is using a VoIP/private branch exchange (PBX) convergence tool as it moves to Internet telephony. Wegener stressed the importance of getting VoIP, telecommunications and network vendors on the same page before starting a major project.
"You really need all three of them around the table if you want to get things resolved," he said. "You need to lay out who's responsible for what from the start, because it never goes 100% smooth."
Yankee Group expects VoIP's share of the market for new installations to rise from 10% in 2001 to 25%.
The city of Houston last month began work on what it says will be the largest VoIP deployment by any government body in the US to date, linking 25,000 phones in a $15.7m (£11m), 18-month project.
Denny Piper, the city's chief information officer, admitted that it will not be easy. "We're going to find some holes in our network, but we would have had those anyway," he said. "That you might run into problems is not justification for not doing it."
Houston's municipal government operates 47 PBX phone systems and 43 separate voicemail systems. It has spent the past five years installing a Cisco Systems network and will also use Cisco as its VoIP vendor.
But even with a single vendor, there are costly redundancy and quality-of-service issues, Piper said. "We're looking at another $2.2m (£1.5m) in incremental network upgrades over the next year," he added.
Steve Leaden, president of telecommunications and networking consulting firm Leaden Associates, believed that protracted VoIP implementations will prove a major challenge for IT executives.
"Every IT department I talk to that's doing this, these guys are on total overwhelm," Leaden said.