VOIP capabilities within Office Communicator Server 2007 from Microsoft can offer significant business advantages for corporations, but it's not all plug-and-play yet.

Global Crossing, which was a private beta user of the unified communications platform, says OCS delivers smoother interconnection of users with each other and the applications they are working from and has the potential for more functionality.

At the same time, though, the software requires custom coding to interface with the company's proprietary applications and VOIP gear made by other vendors.

Microsoft OCS 2007 brings e-mail, instant messaging, presence and most importantly, voice and video all together on a single server. The platform is based on session initiation protocol (SIP), which is the signaling and call-management protocol that likely all VOIP gear will ultimately adopt.

The significant difference between OCS and its predecessor, Live Communications Server (LCS), is the addition of VOIP, so the server can act as an IP PBX. VOIP is also supported in Office Communicator Client so a desktop with an OC client could make a softphone call through OCS to another OC client-equipped desktop, says Chris Collins, Microsoft's product-management director for unified communications.

Microsoft is so keen on breaking into business VOIP it is even selling a stripped-down version of OCS for use in small businesses as a phone system in conjunction with appliance vendor D-Link.

Using OCS as the main PBX for large corporations, though, is still a ways off. Even Microsoft's vice president of unified communications positions OCS as supplemental to PBXs today, offering features such as presence and the ability to embed voice in applications that PBXs lack.

But he says Microsoft does have its eye on pushing PBXs out of the way over time. "They can keep their current system in place, and put Office Communicator next to it and slowly phase out the old one," Gurdeep Singh Pall says.

That is what Mike Fuqua, Global Crossing's senior vice president of strategic development, has done so far with his beta implementation of OCS. He has the software integrated with Cisco Call Managers, so users with OCS can talk to workers who don't have it and with the outside world.

As he phases OCS in across all Global Crossing desktops later this year, he plans to integrate the platform with the Avaya PBXs also in the corporate network.

Equally significant as its PBX functionality is the fact that OCS's VOIP capability can be embedded in applications. So someone working within the Global Crossing order-management/provisioning application called Eon will be able to make phone calls to other workers directly from Eon, Fuqua says.

OCS displays presence information within Eon about who is attached to the network, so workers know who else is available to answer questions when someone needs help, he says. Getting OCS integrated with Eon will take some work by internal programmers at Global Crossing, according to Fuqua, but he expects it to work readily as did the instant-messaging capabilities he embedded in EON from LCS.

Initiating communications directly from within an application keeps workers focused on the task at hand, Fuqua says. Presence also can improve efficiency by reducing the number of unsuccessful attempts to reach others. With presence, people will attempt to reach only those who they know are available. Microsoft calculates that 70 percent of all business calls made with conventional phones don't reach the parties being sought and wind up in voicemail, Collins says.

Microsoft has integrated OCS with its own applications to give more communications options -- for instance responding to e-mails from Outlook. If an e-mail has been sent to five people, all will see the presence status of the others in their copies of the e-mail and can click on icons to set up a five-way voice conference call or a joint IM session, Collins says.

VOIP in OCS is also making corporate mergers easier for Global Crossing, Fuqua says. The day companies are acquired, the new workers will be given OC clients, and their presence information is included in Global Crossing's intranet directory. That will give them communications capabilities with anyone else at the company via instant messaging and PC-to-PC IP softphone calling, he says. The company already sets up communications channels with new companies via LCS, he says.