Buyers of IP PBXs need to look beyond simple voice capabilities to unified communications and make sure the gear they buy will be compatible with applications they will want in the future, experts say. (Compare IP PBXs.)

IP PBXes won’t be just about making phone calls as they become the anchors for UC technologies, which draw instant messaging, presence, collaboration and business-process applications into the mix with voice. (Compare UC products.)

As long as an IP PBX has the software interfaces it needs to integrate with UC platforms, it will be serviceable for the foreseeable future, says Jay Lassman, an analyst with Gartner. That is a major concern among his clients, he says.

Those who may just be moving to corporate VoIP — what Lassman terms IP telephony — are well aware of UC and want to be sure they make the right choice of IP PBX. "They are looking ahead to what will be available in three years and want to know what is their investment protection going to be like if they an IP PBX today." he says.

Click to see: Chart indicating steps toward unified communications

That protection will require that the platforms support open interfaces to all the key applications that create UC, says Phil Hochmuth, an analyst with the Yankee Group. “You need to think of an IP PBX as another data center server,” he says. “How will it work with database servers, with CRM and ERP applications? Look at it as part of a larger IT infrastructure puzzle.”

In particular that means Session Initiation Protocol (SIP), which is not necessarily the signaling protocol used by the top IP PBX vendors today, but that all of them are moving to adopt, Hochmuth says. They are also trying to make their implementations of SIP interoperable with those of other vendors. For instance, Avaya says it performs compatibility testing with other vendors' gear such as phones and with service provider trunks.

This is good for customers but also serves Avaya’s game plan of helping customers link business applications together with business processes, says Lawrence Byrd, director of IP telephony and mobility at Avaya.

It is conceivable using UC for a help desk application to spot a critical problem and automatically launch a voice call, IM or e-mail to notify someone who can deal with it, Byrd says, a process pulling together multiple individual underlying applications.