On that day, internet service providers (ISPs), home router manufacturers and web companies around the world will permanently enable version six of the IP addressing scheme (IPv6) for their products and services, in an attempt to kickstart a global transition to the new internet protocol.

Participating ISPs, such and AT&T, Comcast and the UK's education network Janet, will enable IPv6 for enough users so that at least one percent of their residential subscribers who visit participating websites will do so using IPv6.

Meanwhile, home networking equipment manufacturers, such as Cisco and D-Link, will enable IPv6 by default through their home router products, and Web companies like Facebook, Google and Microsoft Bing will permanently enable IPv6 on their main websites.

IPv6 is seen as critical to the Internet's continued growth, as the current protocol, IPv4, allows for just 4.3 billion IP addresses - a number close to exhaustion due to the explosion of Internet-connected devices. In comparison, IPv6 allows for 3.4 trillion trillion trillion addresses.

As well as accommodating Internet growth for the foreseeable future, IPv6 could also enable the 'Internet of Things' - providing a large enough address pool for every electronic appliance to have an IP address and share data with other appliances in real time without human intervention.

In February 2011, the Internet authority IANA allocated its last batch of IPv4 addresses to the regional internet registries (RIRs), which are responsible for local distribution of IP addresses to enterprises and ISPs. When those stocks of IPv4 addresses run out, as has already happened in Asia, the RIRs will have no choice but to start distributing IPv6 addresses.
IPv4 and IPv6 can coexist, but they cannot intercommunicate, meaning that the two protocols will have to run in parallel - or dual stack - for some time, in order to avoid breakages in the network. However, this relies heavily on Network Address Translation (NAT), which limits the performance of the Internet.

Last June, the Internet Society held a "test flight" for IPv6, dubbed World IPv6 Day, when tech giants such as Facebook, Google and Yahoo and content delivery networks Akamai and Limelight Networks all enabled IPv6 on their main services for 24 hours. The aim was to motivate organisations across the industry to prepare their services for the imminent transition.

The day was hailed as a success, although a small number of people experienced slow page loads. One year later the Internet Society thinks the industry is ready to enable IPv6 permanently.

The reluctance to enable IPv6 could be due in part to the investment required, both in terms of operational costs and the cost of upgrading physical equipment such as broadband modems and set top boxes. However, most companies have been buying kit over the past few years that supports both IPv4 and IPv6.

For example, the tests ran during World IPv6 Day revealed that some networks appear to support IPv6 when in fact they do not. As some operating systems are programmed to try and connect via IPv6 in the first instance, before falling back on IPv4, this caused significant delays for some users.

IDG News Service