DNS

  • Domain Name Servers (DNS) are the Internet's equivalent of a phone book.
  • They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses.


Why use DNS?
  • This is necessary because, although domain names are easy for people to remember, computers or machines, access websites based on IP addresses. 
Working:
  • Information from all the domain name servers across the Internet are gathered together and housed at the Central Registry. 
  • When you type in a web address, e.g. www.jimsbikes.com, your Internet Service Provider views the DNS associated with the domain name, translates it into a machine friendly IP address (for example 216.168.224.70 is the IP for jimsbikes.com) and directs your Internet connection to the correct website.
  • If  one DNS sever doesn't know how to translate a particular domain name. it asks another one and so on, until the correct IP address is returned.


Primary DNS vs Secondary DNS:
Primary DNS
Secondary DNS
It is referred as Master Server.It is referred as Slave Server.
It is responsible for reading data related to the domain zone and also responsible for communication with secondary server.It is responsible for obtaining zone data from the primary DNS server immediately after being set up.
It is the read/write copy of the DNS database.It is the read only copy of the DNS database.
We can add new records and make updates in Primary DNS.We can not add a records it takes directly from Primary DNS.
It has only one zone capacity.It has 255 zones capacity.
It works as a main server for all tasks.It works as a backup server when primary server fails.
Primary DNS responds for all domains.DNS server offers security through redundancy.
Primary vs Secondary DNS example:


 Examples:





Advantages:
  • No need to memorize numbers.
  • Domain name makes/gives a kind of sense to hyper links when a name is given instead of string of numbers.
  • Easy for categorizing, archiving and inturn helping search engines.
Disadvantages:
  • Breakdown of DNS would crash the world wide web through there are many root severs and backup sever targeting DNS severs at particular key locations would do lot of harm.
  • Spoofing DNS would lead to loot of crucial/private data ending up in wrong hands.
Video:


My notes images: