Jan 05

Importance of DNS

Importance of DNS

Domain Name Server (DNS) is a protocol that is used to help internet users identify the websites using much easier and readable domain addresses. Just like a phonebook, where we can use to look up a person and discover their number, DNS allows the internet users to enter a name of the web site and automatically find the corresponding IP address for that web site. This makes DNS as an absolute must to have for internet to work.

DNS records are commonly updated meaning that the corresponding IP address of a web site could change over time and this does not affect the users because the domain will be the same. A DNS record or A or AAAA points a domain or a subdomain to an IP address and a CNAME record points a domain or a sub domain to another domain name. Additionally, DNS also allows multiple hostnames to correspond to a single IP address which can be used for virtual hosting where many hosts are served from a single host. At the same time, a single hostname can also be resolved to many IP addresses which is used for distribution of load among multiple servers.

DNS resolution

When a device connects to a local network, either through an Internet Service Provider (ISP) or a Wi-Fi network, a modem or a router send network configuration information to the device which also includes one or more DNS servers and they will be used by the device to resolve hostnames into IP addresses. DNS resolver is responsible for checking if any hostname information is available in the local cache and if not, DNS resolver will contact series of DNS name servers until it receives the IP address of the corresponding hostname the device is trying to reach. This process is known as DNS resolution of a hostname to an IP address.

Uses of DNS

  • Resolving names of web sites in World Wide Web (WWW).
  • Routing of messages to email servers and webmail services.
  • Multiplayer games.
  • Connecting app servers and databases with a web application.

How DNS works

  1. DNS Query – DNS Query is when a web browser or any other application requests a hostname such as “www.example.com”. Then the DNS resolver responds to this query to find the corresponding IP address matching the hostname.
  2. DNS root servers – The DNS resolver will contact the DNS root server, which has all the information about DNS resolutions to various web sites. If DNS root server does not have any information, the query will be sent to the Top Level Domain (TLD) name server which corresponds to the TLD in the query, such as .com
  3. TLD name server – TLD name server contacts the Authoritative Name server which is responsible for the domain (www.example.com).
  4. Authoritative Name server – Authoritative name server will have the information including the IP configurations for the full domain.
  5. DNS Query resolved – Now that the DNS resolver has learned about the corresponding IP address of the domain “www.example.com”, it returns this information to the web browser or the application.

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