A significant stumbling block to IPv6 adoption may be the IPv4 loyalists who are keen to keep the protocol in preference to the 'new improved' version.

Geoff Huston, senior Internet research scientist from Asia Pacific Network Information Centre (Apnic), belongs to the IPv4 camp.

"We happen to work in an industry that survives on complexity, address scarcity and insecurity," Huston said. "This is where the margins come from, and we are not innovators in this industry any more. We've learnt that optimism doesn't create a business case. All those people disappeared along with the dotcom boom," he said.

Internet Protocol Version 6 is a backwards-compatible replacement for the current Internet protocol, and boasts inbuilt mobility, quality, manageability and security. Its main selling point is that it will increase available address space from about 4 x 109 to 3 x 1038 unique IP addresses, allowing for nearly unlimited numbers of systems and networks.

Huston, who worked at Telstra before joining Apnic, said that although IPv4 as we once knew it has died, and that the Internet Assigned Numbers Authority (IANA) will one day run out of IPv4 addresses, the industry will continue to find ways to market hoarded and unused addresses and make IPv4 continue to work through devices like Network Address Translation (NAT) boxes.

"The death of IPv4 has not really killed the Internet. In fact, far from it, we've managed to make an industry around it. We've already created a business around where we are, not where we want to be. Skype is not a charity and it works in all of this muck. If it couldn't work, complain to me, but as long as it works, I don't see the problem," he said.

Huston said that ISPs are already sitting on low margins and do not have the money to push IPv6 to customers.

"Go to your favourite venture capitalist and say 'I want to be an ISP'. By the time he stops laughing and [finds you want to run] IPv6 - the discussion gets terminated. No one wants to hear this. IPv6 is well ahead of adoption in this market so everyone is deferring. No one is running IPv6, because there is no business case for it," he said, adding that if we really wanted to leave a legacy to our children we'd review the crap we have today which is pretty ghastly and not going to sustain, he said.

"But how do you match that common endeavour with what happens in the office when the product manager gets in your ear and says 'you're over spending again'."

Huston's solution is to sacrifice the long term for the short term.

"Everything over http works just fine right now. NAT could be the perfect success. It was never planned, but it is everywhere and it works," he said.

"When the Internet registries run out of addresses, life will still appear like normal, e-mail will still work, and you won't be forced to start using IPv6 all of a sudden." You will still be able to get addresses, if you pay for them, because a market will appear.

"Anyone that is a clever economic unit will buy and sell. Anyone with class B addresses will figure out that if they band up behind a NAT, they can sell off all spare addresses. So scarcity is just a pricing function and there will be a market in address compression."

With this second stage of the IPv4 market, he said, it could be 2050 before all the IPv4 addresses run out, depending on what modelling method is used.

Cisco's senior technical leader for IPv6 technologies, Tony Hain, begs to differ.

"Network Address Translation (NAT) and CIDR (Classless Inter-Domain Routing) did their jobs and bought the 10 years needed to get IPv6 standards and products developed," he said.

"The end to sustainable growth of the IPv4-based Internet has arrived and it is time to move on. IPv6 is ready as the successor, so the gating issue is attitude. When CIOs make firm decisions to deploy IPv6, the process is fairly straightforward. Staff will need to be trained, management tools will need to be enhanced, routers and operating systems will need to be updated, and IPv6-enabled versions of applications will need to be deployed. All these steps will take time-in many cases multiple years."

Hain said that recent consumption rates of IPv4 will not be sustainable from the central pool beyond this decade, so organizations would be wise to start the process of deploying IPv6 now. Those who delay may find that the IANA pool for IPv4 has run dry before they have completed their move to IPv6.

"Although that may not be a problem for most, organizations that need to acquire additional IPv4 space to continue growing during the transition could be out of luck," he said.