Global carriers will be unable to realise the potential of next-generation networks (NGNs) costing billions of pounds if they do not address standards and interoperability issues, experts warned today.

Speaking at the NetEvents symposium in Evian today, Alireza Mahmoodshahi, chief technology officer at Colt, told delegates: "An NGN by itself whether from Colt or BT that does not take seriously interoperability with other carriers will just not cut it.

He added that, as the world becomes more globalised, we need to work better with each other.

Roger Ward, president of the MultiService Forum, and an officer of the CTO at BT, added: "Interoperability is key to making NGNs work. We are at that point in time when we have reached a paradigm shift."

Ward explained that, for BT's 21st Century Network (21CN), the firm is investing £10bn over five years. "21CN is a massive investment and there can be no going back. Standards are key to that but standards are not going far enough. You need practical implementation agreements to get to that truly multi-vendor interoperability environment."

However, Dean Bubley, analyst and founder of Disruptive Analysis, argued that telcos need to broaden their horizons and consider interoperability with the internet and not just other operators: "Standards are desirable but not always essential. Just look at Skype and Google."

He argued that "there is an elephant in the room" in the form of the internet.

"NGNs need to interoperate not just with other NGNs, but with the internet and the enterprise," Bubley said.

"I would argue that it is more important for BT to interoperate with Skype rather than, for example, an NGN from Telecom Bolivia."

Mac Taylor, founder and chief executive at Moriana Group, pointed out that deployment of NGNs depends on more than just technology.

"In some respects the future of NGNs is more dependent on personal career paths within an organisation and cultural road blocks, rather than just technology," he said.