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DNS

What is a Domain Name System?

According to this article, The domain name system, more commonly known as “DNS” is the networking system in place that allows us to resolve human-friendly names to unique addresses.

In short, DNS tranlates a hostname into an IP address for that host.

A-Record:

It is used to find the address of a computer connected to the internet from a name (domain name). In other words, The "A” record is used to map a host to an IPv4 IP address

Domain Name ---> Registrar ---> IP Address

  • If DNS goes down your site can't be reached by users.

  • DNS records expires

  • DNS is part of the security mechanism for HTTP which includes SSL encryption and cookie privacy

  • DNS record have a TTL (Time to Live) which tells the caches on how long to cache them for

The Resolver:

The DNS client code is built into every OS.

C-Name or FQDN:

It is used to specify that a domain name is an alias for another domain. example www.github.com is an c-name or alias for github.com

Search Domain:

A setting in the resolver configuration that makes the resolver look up names inside a domain

example of DNS worker in action:

  • A record for www.google.com can be found on the name server for www.google.com.
  • NS record for www.google.com resides in the com server which is a `gTLD (Global Top level Domain)
  • The NS for .com are stored in the root servers