Question

What is DNS and what is it used for? How is it structured? What are the implications of this structure? Describe an example DNS query.

Answer 1

DNS: Domain name is an alphanumeric name of a computer in a network, with each name corresponding to a unique IP address.

DNS is used in different platforms. It is used to translate an alphanumeric domain name like wwww.google.com into its corresponding IP address before it used.

Structure of DNS:

Domain name always contains two or more comments separated by "dots".

DNS is divided into three categories:

i) Generic domain: These types of domain defines registered host according to their generic behavior.

Example:

com:-commercial entities

edu:-Educational institution

gov:-Non-military US Govt. institutions

ii) Country Domain: This domain section follows the same format as the generic domain but uses 2 character and region code such as UK(United States) or IT(Italy).

iii) Inverse domain: This domain is used to map an address to a name.

Implications of this structure:

i)DNS provide multiple server instances that can share the load embonpoint against host failure.

ii)DNS can placing one zone server to different administrative domain.

iii)DNS provide redundancy across different organization so that if failure of one organization that will not impact other DNS service.

Example of DNS query:

Suppose a user wants to connect to a computer with the domain name www. google.com then DNS client provide a hostname and DNS resolver responds with a relevant resource or an error message if it cannot be found.

If DNS resolver has any relevant records of domain name in computer cache memory then it returns them.

If DNS server contains a list of all computer names along with their IP address then the server returns the correct IP address to the client computer. Finally connect to the desire computer with domain name google.com using IP address received from DNS server.