Heya, SDK.

Today I'm going to explain IP addresses to you.
You probably already have a basic idea of what an IP address is - a string of four numbers, each ranging from 0 to 254, which identify a computer / server / router on a network. This is the core concept of IP addressing.

For example... you are probably reading this connected to a WiFi router, perhaps your home router.

Your router (and every other) can use an IP address in one of a couple of ranges - the most common being 192.168.x.x - to identify devices on the local network. These are called 'link-local addresses', and route to other devices on the local network, as the name may imply.

These link-local addresses are not unique; there are millions upon millions of devices with the link-local address 192.168.1.2 right now.

This must cause a big problem, right? How would a computer or other device know which one to connect to?

Well, the trick is, link-local addresses are only valid in your local network. (eg. your home WiFi network, or a school / office network)

Your router handles these itself instead of passing them out to the wider Internet - when it sees a request to route to a link-local address, it knows that link-local addresses refer to devices on the local network, so searches for the device with that address (maybe it's your 3DS, or your PC) and routes the connection to it. (This is a massive oversimplification, of course, but it's pretty much how it works.)

This is all well and good, though, but what about the wider Internet? And why don't you see IP addresses all the time?

Well, most of the time, you won't actually see an IP address.
In day-to-day Internet use, you can type in '3dspaint.com', for example, and get straight to 3DSPaint, never having to see an IP address. However, behind-the-scenes, what your computer actually does is asks a special kind of server called a DNS server what IP address the name '3dspaint.com' points to.

In this example, the DNS server will return the IP address '23.253.63.167' - go ahead and type that address into your browser and you should see the HullBreach Studios website! (HullBreach's server hosts multiple websites and differentiates between which one to send to your device by what domain name your device tells the server it requested.)

So there you have it; the basic concept of how the Internet works.

*A WILD IPv6 APPEARED!*

We're not done quite yet; you see, one thing I haven't discussed yet is the fact that there are only 4,294,967,296 IP addresses, and we've pretty much run out. #firstworldproblems

Oh noes, what ever will we do?!

Well... IPv6 to the rescue!

You see, so far, when I've mentioned IP addresses, what I *really* meant was IPv4 addresses.

This is the orignal IP address scheme. However, with us running out of these IPv4 addresses and all, the Internet boffins invented IPv6, which uses 128-bit addresses, giving a total of 2^128 possible addresses, which is a very large number - (don't know how to say it? )

There are so many, in fact, that I have a block of 18,446,744,073,709,552,000 () of them to my namd (through my hosting provider, Verelox) - which is actually the square(!) of the number of possible IP addresses - that's 4,294,967,296 ^ 2, a.k.a. 4,294,967,296 × 4,294,967,296. (If you're interested, my assigned IPv6 block is 2a07:3980:1:600::/64)

This is an obvious advantage over IPv4 as it's highly unlikely that we'll ever run out of IPv6 addresses.

The only problem with IPv6 is that a lot of ISPs (Internet Service Providers) don't support IPv6 connections for residential customers, therefore making its use to everyday people quite limited. Furthermore, some devices *cough*Nintendo*cough* don't support IPv6 at all, though there are ways around this.

Either way, IPv6 is a very exciting prospect. Quantillions of addresses can be handed out at a time left right and centre and we still won't run out for an extremely long long long oong long long long long time. This will be very useful for the rising trend of connected 'Internet of Things' devices, where each device can have its own unique internet-accessible address, avoiding the need for dynamic IPv4 address assignment and NAT (where you to share one IP address between multiple devices by filtering the traffic. It's awkward sometimes)

I hope you enjoyed this, and that I didn't drone on too much.

If you have any queries, leave a comment and I'll do my best to answer them.

Likewise, leave any suggestions for future explanation blogs down below.

Be excellent to each other, and party on, dudes (& dudettes).

(Footnote: You can check if your internet connection supports IPv6 at http://ipv6test.google.com/.)