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Each device connected to the Internet has a unique IP address which other machines use to find the device.
ex:

  • 192.168.1.1 (in IPv4)
  • 2400:cb00:2048:1::c629:d7a2 (in IPv6)

DNS translates domain names to IP addresses so browsers can load Internet resources.

DNS Lookup>  by serving the requested resource record earlier in the DNS lookup. Query

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  • DNS Recursor: Receives queries from client machines:- apps such as web browsers
  • Root Name Server: An index to different TLD name servers - serves as a reference to other more specific locations.
  • Top Level Domain(TLD) Name Server:  (In example.com, the TLD server is “com”)
  • Authorative Name Server:

Caching is done afterwards. by serving the requested resource record earlier in the DNS lookup.

Additional Name Server - subdomain

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where the query is for a subdomain such as foo.example.com or blog.cloudflare.com, an additional nameserver will be added to the sequence after the authoritative nameserver, which is responsible for storing the subdomain’s CNAME record.

The 8 steps in a DNS lookup:

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  1. A user types ‘example.com’ into a web browser and the query travels into the Internet and is received by a DNS recursive resolver.
  2. The resolver then queries a DNS root nameserver
  3. The root server then responds to the resolver with the address of a Top Level Domain (TLD) DNS server (such as .com or .net), which stores the information for its domains. When searching for example.com, our request is pointed toward the .com TLD.
  4. The resolver then makes a request to the .com TLD.
  5. The TLD server then responds with the IP address of the domain’s nameserver, example.com.
  6. Lastly, the recursive resolver sends a query to the domain’s nameserver.
  7. The IP address for example.com is then returned to the resolver from the nameserver.
  8. The DNS resolver then responds to the web browser with the IP address of the domain requested initially.

Once the 8 steps of the DNS lookup have returned the IP address for example.com, the browser is able to make the request for the web page:

  1. The browser makes a HTTP request to the IP address.
  2. The server at that IP returns the webpage to be rendered in the browser (step 10)

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