There have been a number of predictions that say that the Internet address space is going to run out either this year or next. And if you look at the numbers, then it looks like this might well happen soon. We all expect the Internet to see world wide adoption, with the biggest growth in Asia and Africa in the next 10 years. If we assume that “wide adoption” means that 20% of the world population have a device that they can use to connect to the internet, then we would need more than twice the number of /8 subnets than can be accommodated under the currently prevailing IPv4 addressing scheme (some say we’d need over 700 vs. the 256 available).
Traditionally, we have dealt with the shortage in IP addresses by creating private subnets (such as a company or home network) and arranging network address translation (NAT) at the edge. The level of separation between subnets and between each subnet and the wider Internet also provides an opportunity for inserting a firewall to provide more security. So, we have a way of putting off the event of running out of addresses and are doing it with a nice security advantage.
But we are using ever more devices that require a direct connection to the Internet. For example, the number of mobile phones with browsers has exploded. Consumer devices such as games consoles are expected to communicate with others across the globe and from anywhere. A number of innovations in industry, retail, and transport sectors involve devices that can interact with others, and thus require an IP address.
The only solution to the problem is to substantially increase the address space, and IPv6 [RFC 1752] is the way to do this. IPv6 was developed into a standard between 1995 and 2006. In 2007, the OECD produced a ministerial background report on the economic considerations of a switch from IPv4 to IPv6. It identified the need for government action, and acknowledged that there would be a significant costs associated with a switch of this kind. And the benefit from the switch: the Internet keeps working … without brown-outs … but without any new features that can be sold to customers to help pay for the huge necessary investment. No wonder that Internet Service Providers are dragging their feet. And enterprise network managers are equally worried, because renumbering a network is about the most frightening thing for them to undertake: it will break all sorts of things that cannot be predicted. In a period of economic slowdown, such jobs get put off. This state of affairs makes government action and legislation the most likely drivers for IPv6 adoption.
There are also many rumours and stories abound on the differences between IPv4 and IPv6 . I found chapter 2 in “Global IPv6 Strategies: From Business Analysis to Operational Planning” very well written. And it is available for you to read online here. If you are interested in the history of IPv6, the drivers for the change from IPv4 and a clear explanation of how IPv6 will deal with routing, multi-homing, plug and play autoconfiguration, quality of service, mobility, security, and renumbering, then I would thoroughly recommend you take a look at chapter 2 in this book.
OECD report: http://www.oecd.org/dataoecd/7/1/40605942.pdf
“Global IPv6 Strategies: From Business Analysis to Operational Planning”, chapter 2 “IPv4 or IPv6 – Myths and Realities”: http://media.techtarget.com/searchNetworking/downloads/IPv4_or_IPv6.pdf