IPv4 addresses: Less than 10pc still available

The shortage of IPv4 addresses has reached a critical stage, according to the registries that allocate internet numbers around the world.

The Number Resource Organization (NRO), which represents the registries, said on Tuesday that less than 10 percent of all IPv4 addresses remain available, threatening the future network operations of all businesses and organisations unless ISPs and businesses step up their migration to IPv6.

"The limited IPv4 addresses will not allow us enough resources to achieve the ambitions we all hold for global internet access," NRO chairman Axel Pawlik said in a statement on Tuesday. "The deployment of IPv6 is a key infrastructure development that will enable the network to support the billions of people and devices that will connect in the coming years."

However, where previous estimates had IPv4 addresses running out in 2011, it now appears addresses are more likely to be depleted in 2012, Pawlik told ZDNet UK. "That is based on the current growth rate, but there might be big allocation requests coming up — you never know," he said.

There are two versions of the internet protocol (IP), which lets devices talk to each other over networks. Most addresses are based on IPv4, but the newer IPv6 — set live in early 2008 — provides trillions more addresses, which will be needed as the numbers of web users and connected devices multiply.

IPv4 and IPv6 addresses are not compatible. Pawlik said it was technically feasible to make the two types of IP address talk to each other, but it would be best for companies and ISPs to switch to IPv6 as soon as possible, to keep networks stable and avoid complexity when IPv4 addresses run out.

Pawlik said ISPs and businesses have been putting off the switch to IPv6 because the engineering time and costs involved in such a transition meant "there was no real strong business case".

"There are funny characters in there [rather than just numbers] and IPv6 addresses are longer, but engineers are going to have to get over that," Pawlik said. "It is really about securing the future."

Pawlik also conceded that many businesses are putting off the switch to IPv6 because, even when all public IPv4 addresses have been allocated, they will continue to be able to allocate private IPv4 addresses internally. However, he stressed that anyone running public-facing websites will have to make their sites visible as IPv6 addresses, as their users will be on IPv6 addresses in the future.

Google started making its sites available as IPv6 addresses in March 2009, while the EU began its migration in October.