It is only a matter of time when Microsoft’s VoIP dreams come in the way of Cisco’s desire to be the king of enterprise VoIP. Cisco spokespeople say the two companies are going to work together, but some believe that trouble could be brewing.

Cisco already builds these networks, and sells phones with a screen that would, say, allow workers in a store to check inventory and even direct customers to another store that has a particular item in stock. These advanced services are highly profitable for Cisco. But it is exactly the market that Microsoft has its eye on, with new software to manage VOIP networks.

The recent product launch by Microsoft shows that the Barons of Redmond are pretty serious about this whole IP communication thing, and will take on all comers. Their real-time communications server is no different from what Cisco is already selling, aka Cisco IPCC. Cisco CTO Charlie Giancarlo estimates that enterprise VoIP is a $15 billion a year business.

“What it really comes down to is who gets there fastest and who delivers the most secure and adequate solution,” said CIBC World Markets analyst Steve Kamman, noting that Cisco might have an advantage because it actually builds the network.”The extent that Cisco makes it easy to manage in one place across the whole company, they’re going to continue to do well versus fiddling around with thousands of PCs,” he said.

Cisco has become increasingly aggressive in the services arena and is looking to become a one-stop shop for most enterprise needs, putting it in direct competition with some-time partners like Microsoft and IBM.