Domain Name system (DNS) | Hierachical Name Space | DNS

Domain Name System (or Service or Server):

Ø  When DNS was not into existence, one had to download a Host file containing host names and their corresponding IP address.

Ø  But with increase in number of hosts of internet, the size of host file also increased.

Ø  This resulted in increased traffic on downloading this file. To solve this problem the DNS system was introduced.

Ø  It is an internet service that translates domain names into IP addresses.

Ø  Because domain names are alphabetic, they're easier to remember.

Ø  The Internet however, is really based on IP addresses.

Ø  Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address.

Ø  For example, the domain name www.example.com might translate to 198.105.232.4.

Ø  It uses a hierarchical naming scheme and distributed database of IP addresses and associated names.

Ø  If one DNS server doesn't know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.

 Hierarchical Name Space:

Ø  In a hierarchical name space, each name is made of several parts. The first part can define the nature of the organization, the second part can define the name of an organization, the third part can define departments in the organization, and so on.

Ø  In this case, the authority to assign and control the name spaces can be decentralized.

Ø   A central authority can assign the part of the name that defines the nature of the organization and the name of the organization. The responsibility of the rest of the name can be given to the organization itself.

Ø  The organization can add suffixes (or prefixes) to the name to define its host or resources.

Ø  The management of the organization need not worry that the prefix chosen for a host is taken by another organization because, even if part of an address is the same, the whole address is different.

Ø   For example, assume two colleges and a company call one of their computers challenger. The first college is given a name by the central authority such as jhda.edu, the second college is given the name berkeley.edu, and the company is given the name smart.com.

Ø  When these organizations add the name challenger to the name they have already been given, the end result is three distinguishable names: challenger.jhda.edu, challenger.berkeley.edu, and challenger.smart.com.

Ø   The names are unique without the need for assignment by a central authority.
Ø  The central authority controls only part of the name, not the whole.

Domain Name System Architecture