You can also add other features to an OCS phone call. A call may start out as a voice conversation between two parties, then one of the two parties could spark an IM with a third guy to into the conference -- that's about three clicks in Office Communicator. That third guy could IM a couple of other people, at which point the whole group could be moved into a Live Meeting-style Web conference -- again, just a few mouse clicks from Office Communicator. Naturally, OCS tracks whether users are available or not, the lofty term here being "presence management." This is similar to an away message from a chat client, but extends not only to Communicator but also to Outlook 2007 and the other Office clients. Users scheduling an in-house Web conference can easily jump to Exchange 2007's advanced shared calendaring, giving them a quick view of when everyone they want to invite is available.

Once the conference starts, it can happen entirely on the Web, with users joining from their desktops, or a few folks could gather in a RoundTable-equipped conference room, while others tune in from other locations. RoundTable brings all attendees in the conference room into a videoconference through a special extension to the Live Meeting client, projecting the entire conference room in a ribbon-style view at the bottom of the screen (so folks logging in from the outside can see everyone) while presenting the active speaker in a larger view on the side. The new LiveMeeting client even enables meeting managers to record entire meetings or just snippets, both audio and video, to an external server hosted by Microsoft or an internal one should you have a friendly IT administrator with a lot of spare hard disks. All of the communications options are just a few mouse clicks away, and the results are very, very slick.

But the requirements on the back end are substantial. First off, you'll need to prep your existing Microsoft servers for OCS' arrival. The short list includes Windows Server 2003 SP1 running as a baseline, Active Directory running in DNS mode, Exchange Server 2007 Unified Messaging for voice users, a SQL Server behind the OCS installation, and a Certificate Server running for full security with the outside world. And check those advanced features for additional server requirements, such as Speech Server for voice translation. Shops aiming to use OCS as a PBX will need a SIP gateway to connect to the outside world.

Active Directory integration is, frankly, crucial. Accessing OCS features without Active Directory is likely possible, but you'd lose most of the slickness that makes OCS so attractive in the first place. With Active Directory running in the background, OCS administrators can quickly assign OCS capabilities to users and groups, manage federation between organizations, map IP to POTS settings, and more. The nice part is that most of these management features can be accessed via a new Communications tab that suddenly appears within the Active Directory screen once OCS rears its head in the server farm.

Exchange 2007 Unified Messaging allows that sexy integration of voice and e-mail. On the Exchange side, administrators only have to define a unified messaging mailbox policy and then enable the users who are affected.

On the desktop, it's all about Office Communicator 2007, though Outlook 2007 and the rest of the Office 2007 suite are a good idea, too. Someone running a call via Communicator, for example, might pop open OneNote to jot down some notes. OneNote will automatically grab the OCS call information from Communicator, including the subject, date and time, and even the other users on the call. All of a sudden you have to try to lose your meeting notes.

This kind of cross-app communication is OCS' real reason to live. Communicator is the main client interface, but Microsoft's design goal for OCS was to enable one-click communication from as many places within the Office client/server suite as possible. For the most part, Microsoft has succeeded. The price tag is a little high for our taste (especially when you consider all the secondary servers a full OCS implementation will require in an enterprise setting), but for companies that will truly make use of this level of communication flexibility, the greenbacks are well worth it. If you're already running chunks of the Office server suite, then don't buy a SIP PBX or a conferencing platform without trying your hand at OCS first.