One of the inventors of Internet Protocol version 6 (IPv6) has warned that the European Union (EU) should be more cautious in its implementation.

Responding to an EU call for governments to move swiftly towards IPv6 to increase competitive edge, Dr Paul Francis said that European operators must be more careful.

"[Governments] should fully understand how every service they want to offer works with both IPv4 and IPv6. If any given service can be profitably offered with IPv4, then they should only move to IPv6 if relatively near-term cost savings can be clearly demonstrated," he said.

Francis, who is chief scientist at Tahoe Networks, maintained that, since money is limited, the implication is that less money should be spent on other aspects of internet technology that will advance Europe's leadership, for instance new web applications or better access technologies.

"The tone of the reports portray IPv6 as a critical technology for these new applications but, if you read carefully, you are hard pressed to find a single statement that explicitly states why IPv6 is critical," said Francis.

He added that much of the discussion focuses on the difficulty of deploying peer-to-peer (P2P) applications without globally unique end-to-end addresses, which IPv6 provides.

"However, it never comes out and says that P2P does not work without end-to-end addresses, only that it is difficult," said Francis, pointing out that there is not a single internet application that runs over IPv6 and not IPv4.

He explained: "Yes, P2P is easier and simpler over IPv6, but it can work with IPv4 users behind Network Address Translation [Nat] devices.

"For instance, the online gaming industry has been operating P2P games this way since 1998. Furthermore, the use of Nat extends the IPv4 address space almost indefinitely.

"Everybody agrees that a pure IPv6 world would be simpler, cheaper and more efficient than a pure IPv4/Nat world. But nobody can quantify that, nor does anyone clearly understand the costs associated with getting to that world."

He warned that moving to a pure IPv6 would be long and costly. The longer the transition, the more early adopters of IPv6 may be hurt because they will pay during the period of transition.

"Ironically, the US may benefit the most from Japanese and European spending on IPv6," Francis concluded.