UK internet service provider PlusNet is looking for volunteers among its customers to test out a new carrier-grade NAT (network address translation) system to cope with the dwindling supply of IPv4 addresses.

Although the Internet registries are currently in the process of handing out their last batches of IPv4 addresses, in preparation for the transition to IPv6, PlusNet argues that everyone will still need an IPv4 address for the foreseeable future.

“Even if the world switched on IPv6 today there would still be people and applications that don't work under IPv6, some games consoles for example,” the company said in an open letter to customers.

The company is therefore exploring ways to make its existing supply of IPv4 addresses go further.

Carrier-grade NAT is an approach to IPv4 network design where end sites are not given public IPv4 addresses. They are instead given private addresses that are translated to public by middleboxes embedded in the network operator’s network.

This allows the network operator to share a single IPv4 address among multiple customers. However, critics believe that this breaks the end-to-end principle of the Internet and has significant security, scalability and reliability problems.

PlusNet claims that most people won't notice that it is using carrier-grade NAT. The majority of mobile operators already use the technology, the company states, and so most applications will just work.

“The main problem is where you are hosting services on your broadband connection like hosting a website or hosting games (the kind of thing for which you set up port forwarding on your router),” the company said.

It is therefore asking for help from customers to test the system to find out what kind of applications and services work and don't work.

“We're doing testing internally too but with so many devices, applications, games, VPNs, etc. we'll never test everything. With some help we'll try and get as much as we can,” PlusNet said.

While many will regard the move as prudent, others see it as simply prolonging the inevitable. Ultimately all ISPs will have to embrace IPv6, and by beginning the transition now they can avoid a mad scramble in a couple of years.

“All ISPs should be providing proper IPv6 first, and using NAT purely as a stop-gap,” Adrian Kennard director of broadband provider AAISP, told Thinkbroadband. “This will allow innovation to continue and use the end-to-end design of IP, and it will mean services using IPv6 will 'just work'.”