Domain Name System (DNS)

Lookup Mechanism

Root name server

• It is a server that the request must pass through and return the list TLD name server

Top level domain (TLD) name server

• A top-level domain (TLD) represents the first stop after the root zone. In simpler terms, a TLD is everything that follows the final dot of a domain name. For example, in the domain name ‘google.com’, ‘.com’ is the TLD. Some other popular TLDs include ‘.org’, ‘.uk’, and ‘.edu’.

• When a user enters a domain name like ‘google.com’ into their browser window, the DNS resolvers start the search by communicating with the TLD server. In this case, the TLD is ‘.com’, so the resolver will contact the TLD DNS server, which will then provide the resolver with the IP address of Google’s origin server.

Flow

• google.com is typed into the browser, and the browser sends the domain name to the DNS resolver.The resolver queries a DNS root name server.

• The root server responds to the resolver with the address of a TLD DNS server. In this case, it is .com.The resolver then makes a request to the .com TLD.

• The TLD server responds with the IP address of the domain’s name server, google.com (authoritative name server).

• The DNS resolver sends a query to the domain’s name server. The IP address for google.com is then returned to the resolver from the name server. The DNS resolver responds to the web browser with the IP address (142.251.46.238) of the domain requested initially.

DNS Records

Introduction

• DNS records (aka zone files) are instructions that live in authoritative DNS servers and provide information about a domain including what IP address is associated with that domain and how to handle requests for that domain.

NS

• The name server that containing domain information, such as ip

A

• The ip address that the domain name points to (ip v4 format)

CNAME

• The other domain name that points to other domain name

• Use case: share the same ip address to multiple different domain names