In the second article of this series, we look at the steps it takes to resolve domain names across the internet.
In this article let’s look at the steps that occur across the internet when you type a web address in to your browser. We’ll look at the difference between recursive and authoritative servers and how different types of servers interact when you search a domain or web address.
First we need to specify the difference between two broad categories of servers – Authoritative & Recursive Servers. Very simply, Authoritative Servers store actual DNS records, while Recursive Servers communicate between end users and Authoritative Servers.
Broad categories established, now let’s look at a very simplified domain resolution request, but note this is an over simplified example and in a real request scenario, some steps may not occur depending on specific records and caching.
When you type in www.example.com in the address bar and press enter, your browser sends out a request to the internet that is first captured by a DNS server called a DNS recursive resolver which usually sits with your Internet Service Provider (ISP). This resolver acts as your internet assistant by taking the address and trying to locate where the information for that particular address is located.
The DNS resolver sends your typed web address to a DNS server called the DNS root server. The DNS root server looks at the address, specifically the Top Level Domain (TLD) portion or in our case the .com portion ( Other TLD examples are .net, .org or .edu etc.).
After noting the TLD, the DNS root server then sends a request back to the DNS resolver with the address of another type of server, a TLD server which stores the information matching web addresses like www.example.com, to the IP address of the server where they are actually located.
The DNS resolver will send a request to the TLD server that it was given, which will then respond with the IP address of the DNS nameserver which is the place where the actual www.example.com domain is sitting.
Once the DNS resolver receives the details of the DNS nameserver where the www.example.com domain actually sits, it then sends a query to that nameserver, which responds with the IP address for www.example.com. Finally, the DNS resolver responds to the web browser you typed the address into, with the IP address for your domain or website.
In conclusion, there are many steps in the process to resolve a domain name to the IP address, and this all happens in a matter of milliseconds.
In the next article in the series we will look at DNS zone records and how they assist in the process of domain name resolution.
