Today we are going to discuss network addressing. We’ll look at what happens when you type www.google.com in your browser. While the explanation will be simple, the underlying mechanisms that make this happen can be pretty complex.
In order to join any network, a device needs a specific address, just like your street address. Addresses in an IP network take the form of n.n.n.n, where n is a number from 1 through 254. So when you bring your laptop into the school, it might get an address of 10.10.54.234. Once it has an address, it will ignore all network traffic until it sees its own address. At that point it will listen and respond as necessary.
On a typical school day, there are between 6,000 and 8,000 devices attached to the Bonny Eagle network. So you can imagine how hard it would be to remember just a few addresses. So typically we give each device a name, such as HS-Library-3 or library.bonnyeagle.org. But while your device might know its own name, the rest of the network only operates with IP addresses.
That is where a network service known as DNS or Domain Name System comes into play. Each network, like the Bonny Eagle network, has a least one server dedicated to DNS. Its job is to translate the easy to remember name, like moms-iphone, into an address of 10.10.67.122. From then on, all network traffic uses the address. Most networks, Bonny Eagle included, have more than one DNS server. This provides some redundancy in the event of a failure and also faster performance.
While our DNS servers know the names of all the devices on our network, they couldn’t possibly know the millions and millions of device names all over the world. So think again about your street address. A post office in Utah can’t possibly know your address in Buxton. The Utah post office would send the letter to a processing center where it can be forwarded using the Zip Code. The same is true for DNS. If our DNS server doesn’t recognize the name, it forwards it to one of a few public DNS servers to be decoded. Those few servers don’t know all the device names either, but they can sort out .com from .org, etc and they will forward to another DNS server that can narrow it down more, like this name is in Canada and that name is in Maine. Once the name is decoded into an IP address, that address is sent back to our DNS server, so that your device can use the address.
So the next time you type www.google.com, remember that before you can go to that web page, your device has forwarded that name, through our DNS server, to several others which have returned an address like 127.217.2.4 which your browser then uses to direct your request. And that all happens in milliseconds...before you can even hit the Enter key.