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The Worst VoIP Gotchas: Page 3 of 7

Even basic steps like taking inventory and network testing have their pitfalls. Inventory requires sorting out if existing telephony gear has any value, whether the company needs more or different switches, and what the strategy should be for software additions and upgrades. But there tends to be a lot of confusion around what can and can't stay, warns Tom Thomas, a senior solutions architect at consulting firm Dimension Data. Also, companies need to assess their networks for available bandwidth and quality of service, taking into account the metrics that come preinstalled on networking equipment and on network-management tools like those offered by Network Instruments, Network General, and others, to make sure the networks can handle the additional load of delay-sensitive voice traffic. And not all network-testing tools work for VoIP tasks, some administrators find. The checklist of things to consider is long. VoIP signals often are compressed so they take up less bandwidth, but too much compression reduces voice quality. A network administrator needs to consider whether to go with G711 compression or G729, which applies higher compression and consumes less bandwidth but offers poorer voice quality. Vendors' descriptions of technologies and features can vary widely, too, creating confusion among customers.

Snap, Crackle, Pop

One gotcha is to assume that any new problem is the result of the VoIP network. In some cases, the fault might lie in the connection between the VoIP network and the public switched-telephone network. Testing before fixing is key to discovering the root of a problem. Advocate Health Care, a group of hospitals and clinics throughout Illinois, started switching to VoIP in late 2002 to cut the phone bill and the cost of employee support. The company has reached a result it likes: Now, when an employee changes offices, the support staff doesn't have to go into wiring closets and mess with phone connections. Employees take their phones with them, because a phone's identity is managed on a server, not in a wiring closet.

But Advocate Health Care had to work out some glitches first. When Gary Horn, enterprise architecture and network security director, and his team began testing the system, clicking, popping, and echoing made calls unintelligible, and the echo was so bad callers couldn't understand what the other person was saying. "It would be like the worst type of cellular call you've ever heard," he says.

Horn assumed the problem happened on all the company's phone conversations, but he discovered that only calls that crossed over to the public phone network had quality problems; intraoffice calls were fine. After a few days of testing and tweaking scenarios, his team found they needed to install echo cancelers where the public phone network met the VoIP network. After installing the new hardware, Advocate spent a few days testing the network with network-management tools during the day and reconfiguring and testing the echo cancelers' timing elements in the evenings.