DNS

Describe DNS resolution workflow in high-level

Difficulty: unrated

Source: bregman-arie/devops-exercises by Arie Bregman

Answer

In general the process is as follows:

  • The user types an address in the web browser (some_site.com)
  • The operating system gets a request from the browser to translate the address the user entered
  • A query created to check if a local entry of the address exists in the system. In case it doesn't, the request is forwarded to the DNS resolver
  • The Resolver is a server, usually configured by your ISP when you connect to the internet, that responsible for resolving your query by contacting other DNS servers
  • The Resolver contacts the root nameserver (aka as .)
  • The root nameserver either responds with the address you are looking for or it responds with the address of the relevant Top Level Domain DNS server (if your address ends with org then the org TLD)
  • The Resolver then contacts the TLD DNS. TLD DNS might respond with the address you are looking for. If it doesn't has the information, it will provide the address of SLD DNS server
  • SLD DNS server will reply with the address to the resolver
  • The Resolver passes this information to the browser while your OS also stores this information in the cache
  • The user cab browse the website with happiness and joy :D