Computer Science Principles The Internet - 03 Addressing and Routing Information - 04 The Domain Name Server and DNS

IP addresses are a key part of the Internet, that's why it's called the Internet Protocol.

But for humans, they aren't very intuitive, so there needed to be a way for humans to be able to take phrases that we understand, and have them mapped to IP addresses for devices, and websites around the world.

The solution is a domain name.

The domain name is a sequence of phrases that map to a giant Internet-wide database of IP addresses.

So for a website like www.dougwinnie.com this is the domain name for the website.

When you enter that domain name into your browser, you send that request to something called a DNS, or Domain Name Server, this server holds a cache of tons of domain names, and their matching IP addresses.

But there isn't just one DNS, there are lots of them throughout the Internet.

As new domains are created, and as old ones change, those changes are recorded by a DNS, and they spread throughout the Internet.

If you send a request to a DNS for www.dougwinnie.com and it doesn't know what it is, it'll ask another DNS if it knows, and continue to ask until one does.

It'll then save the information to use later, and then send the corresponding IP address back to you, and then send the request to access the server using that IP address.

The process of translating a domain name to an IP address is called DNS name resolution.

You can completely skip this process if you want to.

For instance, if you wanted to reach google.com you could simply enter in the IP address directly, but remembering google.com is a whole lot easier than remembering the IP address.

The domain name is broken down into a few parts, the last part of the domain name is called the top-level domain, these are managed by the IANA, or Internet Assigned Numbers Authority, so for my website, www.dougwinnie.com the .com is the top-level domain.

Some websites, for example, www.bbc.co.uk use two-letter country codes, and an additional code in this case, the .co before it.

Next is the host name, or dougwinnie this is the name of the collection of servers under the dougwinnie name.

A domain can have multiple servers under it, for instance, it can have a web server, an e-mail server, file transfer server, or multiple other web servers.

To help organize these, a site has a subdomain, so again, in the website name, www.dougwinnie.com the www is the subdomain representing the web server, which has a unique IP address associated with it.

This is different than my e-mail server, which would be smtp.dougwinnie.com or other servers that are under my domain.

With the use of top-level domains, domain names, and subdomains, we have a way for humans to remember servers throughout the Internet, but it is the Domain Name Servers, or DNS, that perform name resolution to translate those domains into IP addresses that allow billions of devices to communicate with each other.