VoIP systems vary in so many ways that businesses need to comb through the gory details of what vendors offer to make sure they get the features and functions they need, attendees were told at VoiceCon Orlando 2008.

Potential customers were urged to consider factors they might tend to overlook, including whether systems can be made resilient to failures, how many devices are needed to build the system, whether they are energy-efficient, whether phones offer all the features customers want, and how well they support cell phones as PBX extensions.

These tips came out during a panel discussion of bids that were presented by a group of vendors on a hypothetical RFP put together by Allan Sulkin, president of TEQConsultant Group, who led a tutorial on the subject. (Compare IP PBXes.) 

There are some basics such as redundancy of the IP PBX that businesses must seek, Sulkin said. "If you don't get dial tone, nothing counts," he said. The good news about such redundancy is that it's more affordable than it used to be. "It is a fraction of the cost it was 10 years ago," he said.

Businesses also should make sure phone service in a branch office will survive by failing over to another site if primary call-control gear or WAN links go down. Customers have to pay a lot for this type of bullet-proofing, Sulkin said, but it's worth it. "They're not going to save you money, in fact these systems cost you more money," he said. But not being able to continue business if a site fails is even more costly. The U.S. Department of Homeland security requires failover sites that can continue business in the case of disasters, he added.

Sulkin also recommended looking for consolidated functionality on VoIP servers. Some vendors put multiple functions on a single server, which saves on electricity when compared with vendors that split applications among multiple servers. The more servers, the more maintenance and the more energy used, Sulkin said. Gear is trending toward being more energy efficient, Sulkin said, so when buying, consider power consumption.

Certain network infrastructure also can help energy savings, the panel noted. Some Power-over-Ethernet switches, for instance, can shut down power to phones and wireless access points during off hours when nobody is at work to use them.