The Internet has run out of Internet addresses... sort of. Perhaps you've heard the news: the last blocks of IPv4 Internet addresses have been allocated. The fundamental underlying technology that has powered Internet Protocol addresses (ever seen a number like 99.48.227.227 on the web? That's an IP address) since the Internet's inception will soon be exhausted.

A new technology will take its place, though. IPv4's successor is IPv6, a system that will not only offer far more numerical addresses, but will simplify address assignments and additional network security features.

The transition from IPv4 to IPv6 is likely to be rough, though. Most people are unfamiliar with IPv4 and IPv6, much less the potential impact the switch to IPv6 may have on their lives.

That's why we've compiled this short guide to IPv4 and the eventual transition to IPv6. We explain the two versions of IP and why they matter. We also go into detail on what you can expect in the next few years as billions of websites, businesses and individuals make the switch to the new era of the Internet.

IPv4 & IPv6 Q&A

Q: What is IPv4? A: IPv4 stands for Internet Protocol version 4. It is the underlying technology that makes it possible for us to connect our devices to the web. Whenever a device access the Internet (whether it's a PC, Mac, smartphone or other device), it is assigned a unique, numerical IP address such as 99.48.227.227. To send data from one computer to another through the web, a data packet must be transferred across the network containing the IP addresses of both devices.

Without IP addresses, computers would not be able to communicate and send data to each other. It's essential to the infrastructure of the web.

Q: What is IPv6? A: IPv6 is the sixth revision to the Internet Protocol and the successor to IPv4. It functions similarly to IPv4 in that it provides the unique, numerical IP addresses necessary for Internet-enabled devices to communicate. However, it does sport one major difference: it utilizes 128-bit addresses. I'll explain why this is important in a moment.

Q: Why are we running out of IPv4 addresses? A: IPv4 uses 32 bits for its Internet addresses. That means it can support 2^32 IP addresses in total — around 4.29 billion. That may seem like a lot, but all 4.29 billion IP addresses have now been assigned to various institutions, leading to the crisis we face today.

Let's be clear, though: we haven't run out of addresses quite yet. Many of them are unused and in the hands of institutions like MIT and companies like Ford and IBM. More IPv4 addresses are available to be assigned and more will be traded or sold (since IPv4 addresses are now a scarce resource), but they will become a scarcer commodity over the next two years until it creates problem for the web.

Q: How does IPv6 solve this problem? A: As previously stated, IPv6 utilizes 128-bit Internet addresses. Therefore, it can support 2^128 Internet addresses — 340,282,366,920,938,000,000,000,000,000,000,000,000 of them to be exact. That's a lot of addresses, so many that it requires a hexadecimal system to display the addresses. In other words, there are more than enough IPv6 addresses to keep the Internet operational for a very, very long time.

Q: So why don't we just switch? A: The depletion of IPv4 addresses was predicted years ago, so the switch has been in progress for the last decade. However, progress has been slow — only a small fraction of the web has switched over to the new protocol. In addition, IPv4 and IPv6 essentially run as parallel networks — exchanging data between these protocols requires special gateways.

To make the switch, software and routers will have to be changed to support the more advanced network. This will take time and money. The first real test of the IPv6 network will come on June 8, 2011, World IPv6 Day. Google, Facebook and other prominent web companies will test drive the IPv6 network to see what it can handle and what still needs to be done to get the world switched over to the new network.

Q: How will this affect me? A: Initially, it won't have a major impact on your life. Most operating systems actually support IPv6, including Mac OS X 10.2 and Windows XP SP 1. However, many routers and servers don't support it, making a connection between a device with an IPv6 address to a router or server that only supports IPv4 impossible. IPv6 is also still in its infancy; it has a lot of bugs and security issues that still need to be fixed, which could result in one giant mess.

Nobody's sure how much the transition will cost or how long it will take, but it has to be done in order for the web to function as it does today.