Voip system layout

Factors to weigh in setting up VoIP environments are not always obvious.

When network executives evaluate their networks to see if they are ready for VoIP, they must look beyond the factors that jump to mind immediately say those who have been through the process.

Checking a corporate LAN to determine if it has enough bandwidth and can support quality of service (QoS), determining a source of power for phones and integrating an IP PBX with the traditional PBX are all a necessary part of the drill.

But evaluating WAN services, the role of wireless voice and ongoing funding for voice services are among the less obvious factors that should be considered, experienced users and experts say.

Potential VoIP users might decide that powering IP phones via an Ethernet cable feeding the phone - Power over Ethernet - is the way to go, says VoIP consultant Gary Audin, president of networking integrator Delphi, who spoke at the recent Voice on the Net show. But other equipment, such as videoconferencing gear, wireless access points and IP security cameras, someday might become part of the corporate plan and increase demand for powered lines. "Think longer term," Audin says. "You may need more [powered] switch ports than you think."

Similarly adding wireless IP voice capabilities can rapidly increase the demand for wireless access points that previously handled only data, Audin says. "More access points means more ports on LAN switches, and that means more cabling."

Wireless VoIP phones also require a careful assessment of available wireless spectrum, says John Haltom, network director for technology management for Erlanger Health Systems in Chattanooga, Tenn., which runs hospitals. Wireless telemetry of patient vital signs and wireless control of medical devices such as ventilators must be studied to avoid bandwidth conflicts that could have dire consequences. Careful bandwidth management in areas where these sensitive devices are in operation is a must, he says.

Designing the layout of wireless access points also requires care to ensure reliability as doctors and nurses move around, Haltom says. One access point supports six to eight simultaneous calls, so if more calls are likely to come from a given area, more access points will be needed. To determine this demand, "I go people-watch," he says. That is, he stands in an area to see how many people use the phones as part of a trial actually make calls at any given time.

QoS is another important consideration that should be measured on the wide area and the IAN if voice traffic is to be sent between corporate sites, says Ron Pike, telecorn manager for EDAW, an urban planning firm in San Francisco. The company is in the process of installing a 600-phone ShoreTel VoIP network.

Sending IP voice between company facilities can save long-distance charges, particularly on international lines. He knew two years ago when he was studying the problem that his provider, Qwest, couldn't provide it. But now it can, and he recommends evaluating and upgrading WAN services with guarantees to ensure the necessary QoS.

He also set up queuing on outbound packets as they are routed onto the WAN so voice gets priority and delay of voice packets within EDAWs network is minimized.

This isn't a concern tor all corporations, however. Phil Brody, CTO of Clark County Nev., Public Schools, says he lucked into a WAN that was friendly to VoIP. Two years ago when he started considering Volpthe district had just installed a Gigabit Ethernet WAN among the county's schools, which now number 450.

But he did run into other concerns. The LAN infrastructure dictated that VoIP be limited to the WAN and that traditional telephones be kept within the schools, using a gateway to connect to the IP network. Keeping IP phones functioning during power outages called for uninterruptible power supplies, an unacceptable cost to the district. Their maintenance alone was enough to kill the idea because the school committee frowns on substantial continuing costs as part of any IT project, he says.

Audin agrees IP voice implementations require back-up power to keep voice reliability high, but backup is needed only for 5 to 20 minutes. After that, if the electricity stays off, temperatures in equipment closets will start to rise beyond the point at which gear should stay in use, he says.

He also says network power should be overestimated for times when a VoIP system has crashed and needs to come back online. Restarting IP phones requires that each phone re-register with the call server and get an IP address. All the phones becoming active at once will create a temporary drain on the power system.

Brody recommends a careful analysis of voice services such as Centrex to determine if converting to VoIP can save money Evaluation of the Clark County schools' infrastructure revealed that it had 9,000 Centrex phones, and use of Alcatel IP PBXs has reduced that to 1,200, he says.

For all the work that goes into planning, users say they gain operational benefits that can translate into savings. Pike says putting in a VoIP network saved $40,000 over what traditional phone gear would have cost, and management savings come to $10,000 per month. Employee productivity increases amount to $9,500 per month, he says.