Unified communications offers the potential for anywhere, anytime connectivity between employees and the enterprise. But as the InteropLabs hotstage team found in piecing together more than a dozen commercial and open-source voice, data and messaging platforms, the technology is still at a relatively early stage, and today represents more promise than practice.

The team defined unified communications as the ability to be contacted using any method of your choosing. It's understandable if that definition sounds a bit like the one for unified messaging, once considered the Holy Grail of messaging.

With unified messaging, the key idea was that a single piece of client software or hardware could receive all messages for a given user. An oft-cited example was having voice mail delivered to an e-mail in-box.

Unified communications adds three new elements not present with unified messaging: presence, instant messaging and mobility.

Presence -- the ability to signal availability and, perhaps, willingness to communicate -- is arguably the most important of the many unified communications building blocks. The status messages in instant-messaging clients (available, busy, on the phone, out to lunch, and the like) are the best-known examples of presence information.

Instant messaging (IM), once viewed with skepticism by enterprise network managers, also has become a mainstay in enterprise networks. This capability comes by way of corporate messaging servers inside as well as through popular Internet-based services such as AOL Instant Messenger and Yahoo Messenger.

Mobility goes well beyond just delivering e-mail to BlackBerrys and other smartphones. Many phones and other portable devices today use GPS or other location-finding technologies that can help enterprises enhance business communications. For example, a fleet of mobile workers can be alerted to avoid traffic jams and IT staff can monitor server and network operations from an ever-expanding list of mobile devices.

The IETF has described two protocols -- SIMPLE (Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions) and XMPP (Extensible Messaging and Presence Protocol) -- to deal with presence, messaging and mobility. As the InteropLabs team discovered in building different systems, though, not all parts of either protocol are fully defined, and not all systems support both protocols.