13. Domain Name System

Domain Name System (DNS)

Understanding DNS

Fully Qualified Domain Name (FQDN)

A Fully Qualified Domain Name (FQDN) consists of three parts - the hostname, domain, and top-level domain (TLD). The format looks like so,

[host name].[domain].[tld]

For the FQDN www.udacity.com - www is the hostname, udacity is the domain, and com is the top-level domain.

Other examples of FQDNs include:

  • www.wikipedia.org
  • www.baidu.com
  • maps.google.com
  • news.yandex.ru

FQDNs?

Which ones among the following can be acceptable forms of FQDNs?
SOLUTION:
  • www.udacity.com
  • www.example.com
  • test.t123.udacity.com
  • en.wikipidea.org

IP Address?

Given an FQDN (Fully Qualified Domain Name), what could be the format of it’s IP address:
SOLUTION: 54.68.115.100

DNS in which OSI Layer?

Which layer does the DNS server belong to in the OSI model?
SOLUTION: Application (Layer 7)

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