The world's largest IT and communications vendors are divided in the way they intend to offer unified communications.

Unified communications is an evolution of voice/data convergence that aims to bring together voice, data, video and presence features into a single system to make an organisation's technology infrastructure simpler and its workers more productive.

All of the major vendors offer some form of unified communications, but they're starting to differ significantly in how they plan to deliver it.

Microsoft, which has just launched its Office Communications Server 2007 offering, believes that the intelligence behind unified communications should be contained in the endpoints, whether that is a desk phone, mobile device or a PC.

PBX vendors notably including Cisco disagree. They say the network is fundamental to the success of unified communications.

* across a network, and you can't manage that network *then you have a problem*," said Warren Barkley, Microsoft's group programme manager for unified communications.

*, then you have flexibility."

* by adding features to the network," the spokesperson added, citing quality of service, network management tools and multiple codecs as three examples.

Cisco's unified communications offering revolves around its CallManager PBX software.