The world is running out of IPv4 Internet addresses, without which the Internet can't function in its existing form.This has been known for some time, of course, but the situation has become a little more urgent with the news that in October and November, nearly all of the remaining blocks of addresses were assigned to various Regional Internet Registries (RIR) around the world.The allocations brings the total number of available blocks to an almost depleted level, and potentially triggers an "end days" agreement in which most of the remaining blocks are automatically assigned to the five RIRs.In other words, there's nothing left. Almost all possible IPv4 Internet addresses have been assigned--all 4,294,967,296 of them.Although of concern on a global scale, the IPv4 depletion is less of an immediate concern on the ground in homes and businesses. The addresses assigned to the RIRs are handed onto Internet Service Providers and organizations within each of the countries the RIRs cover. As such, there's no immediate crisis until the RIRs themselves have assigned all their addresses.However, if the number of Internet devices keeps growing (and it's extremely certain it will, with the boom in smartphones and tablet devices) then we're almost certainly going to see this within a year or two. The solution is to switch to IPv6, which has been widely heralded for about 10 years and brings with it about 340 trillion addresses--arguably enough to last the world for a century or two. The trouble is that organizations are extremely hesitant to do so. The number of Websites offering IPv6 entrances barely breaks into the two-digit range.Additionally, you might have noticed that your ISP has yet to send you any correspondence about the need to migrate to IPv6. I recently switched to a new service provider and received a cutting-edge new router, for example, but there's no sign of any IPv6 functionality--either on the LAN-side on the hub or gateway component, or the WAN-side, or on the router or DSL connection.Most major operating systems are entirely compatible with IPv6 and have been for some time, although without widespread deployment it's not yet possible to see how effective such technology is. It's not cynical to expect a bug or two.The rather strange desire to avoid switching to IPv6 has even lead to reports that some Internet Service Providers are enacting Network Address Translation (NAT) at their data centres. In other words, their customers at homes and businesses are being given addresses that are routable only on the ISP's network, and not on the wider Internet.To simply even further, this means that while such customers will be able to browse the Web and grab e-mail just like everybody else, they'll be unable to use file sharing services, or some services such as video conferencing--effectively, they'll be denied any service that involves one computer directly talking to another across the Internet.It's a little like being only half a person on the Internet. Some commentators have suggested that it turns a user into nothing more than a content consumer, who can be fed data by their ISPs, but who doesn't have the freedom to go out and fetch what they want, or experience new services that require a genuine, routable IP address.Of course, not all IPv4 addresses that have been assigned are in use. In fact, the ratio of assigned to in-use addresses is probably lower than many might think. I suspect many organizations are holding onto IP addresses they've been assigned by their ISP or RIR, but have no intention of using. It simply makes business sense to do so in order to prepare for possible future developments. This has certainly been the case at businesses I've worked at in the past.Some kind of amnesty whereby organizations surrender unused addresses is a possibility, but it's extremely unlikely to become a reality. If nothing else, the biggest question would be who would organize and administer such a scheme, and what financial benefits they would receive (and who would pay).Any measures such as this can only be temporary because, as must be obvious, IPv6 is coming whether we like it or not. It's simply the most sensible and correct solution. If you haven't already, get in touch with your Internet Service Provider and ask when they're planning a switch to IPv6, and what the implications will be for you. Will you need a new service contract, for example? New hardware?Additionally, it might be wise to start experimenting with IPv6 addressing within your organization; there are many books and guides out there explaining how, and it's surprisingly easy to do.Keir Thomas has been writing about computing since the last century, and more recently has written several best-selling books. You can learn more about him at http:\/\/keirthomas.com and his Twitter feed is @keirthomas.