IP addresses are what computers and other networked devices use to identify each other on the network. This network could be your home wifi network, with two computers, a couple of iphones, a printer, and your ADSL router, or it could be the entire internet, with millions of connected devices. IP (version 4 – the “normal” version) addresses are made of 32 bits (thirty-two ones and zeros), written in the form of four “octets” (8 bits, or ones and zeros), separated by dots. Each octet can be any number from 0 to 255, because this is the number of different potential combinations of ones and zeros if you have eight in a row, like 11001001, for example.
So, if each number can be 0-255, and you have four of these numbers, there are 4,294,967,296 different potential addresses. Nearly 4.3 billion. That’s quite a lot, but not enough.
A home network might use a range of IP addresses that look like 192.168.1.x (where x can be anything from 1 to 254), and a big business network might look like 10.x.x.x or 172.16.x.x. Because you can change the numbers where the x’s are, you can give your network the ability to have different numbers of things connected. Being protected from the internet (a “private” network), these addresses can be (and are) used over and over again in homes and businesses all over the world. There are internet “rules” that tell people what IP addresses you should use.
Just so you know, the address 127.0.0.1 always means “loopback” or “localhost” or “home” – it’s commonly used for troubleshooting, as it is effectively the device’s own IP address. If you want to reach all the computers on a network, you use the IP address 255.255.255.255, or the “broadcast” address.
But on the internet, an address will more usually look a little different, and could be something like 126.96.36.199 (google.co.uk), 188.8.131.52 (this website), or 184.108.40.206 (stanford.edu). Everything on the internet needs to have a unique IP address, from websites, email servers, itunes, internet radio stations, your iphone, and your home ADSL router. There are some clever ways that internet service providers conserve the number of IP addresses they need to use, by re-using IP addresses that haven’t been used in a while (which is why your home IP address may change every now and then), or using “network address translation” techniques (essentially giving out “private” IP addresses and re-routing them) so that multiple devices can use the same “internet” IP address.
However, partly because there are increasingly more and more devices connecting to the internet, more servers, and more websites, but also due to IP addresses being handed out in blocks (resulting in many not being used, but not available for use by anyone else), we’re running low. Current estimates put the running out date as early as February 2011, but by clawing back some of the wastage, and using Network Address Translation, the internet should be safe for a while.
Long term, however, we need a new system. That system is IP version 6, which instead of 32 bits per address, uses 128 bits, and therefore supports 2128 or approximately 3.4×1038 unique addresses. By comparison, this amounts to approximately 5×1028 addresses for each of the 6.8 billion people alive in 2010. Actually, the primary aim of IPv6 was not really to provide such a huge number of addresses, but rather to enable devices to more simply allocate addresses, improve routing efficiency (less requirement to fiddle around with address translation or port forwarding), and add clever features such as authentication and data integrity.
Oh, because I know you’ll ask, IPv5 was an experimental streaming protocol, which is why we’ve gone from IPv4 straight to IPv6.
Globally, IPv6 is still very much in its infancy, with largely only the internet big players such as google beginning to roll it out. If you have new hardware and Windows Vista or 7, however, you can use it quite effectively in your private home network. On the internet itself, there’s not that much around yet. Facebook have an IPv6 address at http://www.v6.facebook.com/ and google have theirs at http://ipv6.google.com/, but without an internet-facing IPv6 connection, you won’t be able to get to those links, yet, as there are some issues to be overcome in combining the two addressing protocols. Possibly the biggest and most notable use so far of IPv6 was the 2008 Olympic Games – http://ipv6.beijing2008.cn/en (IP addresses
2001:252:0:1::2008:8), and all the network operations of the games were conducted using IPv6.
In a few years’ time, we’ll all be using IPv6 in one way or another, by using 4G mobile phones, connecting our homes to high-speed internet, accessing new websites and web services, and more; though IPv4 is going to be around for a long, long time.