How it works
Internet devices communicate with each other using IP addresses, which are numerical addresses. People don’t need to know them, domain names are enough. Due to DNS, browsers translate domain names into IP addresses. DNS is like a special database which binds domain names to numerical addresses. A DNS query is a web browser’s request for an IP address to a server.
Types of DNS servers
Authoritative DNS. Authoritative DNS server responds to DNS queries, translates domain names into IP addresses and enables computers’ communication with each other. It also provides update mechanisms for managing public DNS names.
Recursive DNS. Users don’t send queries directly to authoritative DNS servers, but they connect to a recursive DNS resolver. Recursive DNS doesn’t store records and acts like a proxy which delivers information to you. If a recursive DNS resolver receives a query for an IP address it already has in its cache, it sends the requested data on the source or the IP address. Otherwise, it forwards the query to one or several authoritative DNS servers.
DNS root servers
DNS root servers are also called top level DNS servers. Initially they were located in North America, but later DNS root servers appeared on other continents: in Europe, South America and Africa. There are more than 10 DNS root name servers. The DNS root servers have backup copies, and this ensures general Internet reliability. Thus, there are about 150 root servers including their copies. It’s worth noting that the DNS architecture was developed in the early 1980s and it has hardly changed since then.