Expanding on their relationship, Microsoft and Hewlett-Packard are forging ahead in unified communications, the companies announced at Interop on Tuesday. The move is an apparent bid to take on Cisco and IBM from several new angles, including HP's first foray into IP desk phones.

The two companies will commit up to $180 million in co-development, professional services, and joint sales and marketing of a comprehensive unified communications suite with several new products and services, plus enhanced interoperability and support for Microsoft Office Communications Server (OCS) on a number of HP hardware platforms.

The short-term market for UC is an uncertain one, as many companies aren't breaking ground on huge new projects unless they expect significant cost savings. Cisco's UC revenue declined 7% last quarter, but Microsoft has said that its unified communications business continues to grow.

Forrester: Rosy Forecast For UC Market

Over the longer term, it's a more sure bet. A recent Forrester Research report predicts the UC market will grow 35.9% annually between now and 2015.

HP and Microsoft have a pre-existing unified communications relationship, though smaller than the partnership being announced Tuesday. HP offers managed services for Microsoft OCS and Office Communicator and an architecture-planning tool for OCS.

A number of HP case studies and white papers published online describe how HP hardware and services support OCS, and HP has long sold services and tools to manage and deploy Microsoft SharePoint and Exchange.

The new deal, however, will significantly increase that collaboration. Joint teams will be tasked with working together on new products and services related to SharePoint, Exchange, OCS, and HP ProCurve networking products.