End-users will increasingly rely on integrated Lan and Wan services from telecoms carriers over the next few years, according to research by Frost & Sullivan.

However, providers of converged voice and data and security services face scepticism from IT managers, and technical barriers posed by legacy systems.

But the analyst added that a lack of resources in corporate IT departments is forcing more firms to look at cutting network management costs.

Niamh Spillane, research industry analyst at Frost & Sullivan, said: "The benefits for companies are reduced complexity and more efficient use of employees' time and resources.

"These are soft benefits and not very measurable, though, and it will be difficult for service providers to quantify return on investment to chief finance officers."

Some firms may see the advantages of having a single supplier, a single point of contact and a single bill for the telephone and data services they lease.

But others will worry about the reliability and security of carrier infrastructure, and the provider's ability to quickly get the network back up and running if there is a failure.

As well as converged voice and data services, more firms are starting to trust carriers with the implementation, but not the management, of their network security, according to Ian Mashiter, chief executive of telecoms equipment vendor Quarry Technologies.

Tom Fellowes, sales director at converged reseller Spitfire Technology Group, said: "We have a separate IT networking business. We have people who are Lan and Wan engineers, and they go out to sites and get their hands dirty. I can't imagine someone from a telco or an ISP doing this.

"We don't see people leaping into integrated Lan and Wan offerings. We tend to get contracts through support contracts first, and then we sell them connectivity later."