Internet Domain Name Systems - Internet Technologies

What isInternet Domain Name Systems?

Overview

Before DNS is not in existence, there is a Host file having the host names and their corresponding IP address which everyone used to download. As the hosts are increasing, the size of the file is also increasing resulting increase in traffic for downloading the file. DNS is introduced to solve this problem.

DNS is used to resolve the host name to an IP address using hierarchical naming scheme and distributed database of IP addresses and associated names.

IP Address

IP Address is distinctive logical address allocated to a machine in network. Following are the properties of an IP Address.

  • IP address is the distinctive address allocated to each host present on Internet.
  • IP address is 32 bits (4 bytes) long.
  • IP address comprises of two components: host component and network component.
  • IP address having 4 bytes is represented by a number from 0 to 255, delimited with dots. For example 137.170.4.124
  • Domain names are easy to remember than IP address which is 32-bit. For example, entering an email address always takes a symbolic string such as webmaster@wisdomjobs.com.

Uniform Resource Locator (URL)

URL is the web address to uniquely identify the document in the internet.

Document can be a image, audio, web page, video or anything else.

For example, www.wisdomjobs.com/internet_technology/index.html is an URL to the index.html, stored on wisdomjobs web server under internet_technology directory.

URL Types

There are two forms of URL as mentioned below:

  • Absolute URL
  • Relative URL

ABSOLUTE URL

It is the resource’s complete address on the web. It contains protocol, server name, path name and file name.

For example http:// www.wisdomjobs.com / internet_technology /index.htm. where:

  • http is the protocol.
  • wisdomjobs.com is the server name.
  • index.htm is the file name.

How to handle the file is known by the protocol used. Apart from http, we have other protocols as well.

  • FTP
  • https
  • Gopher
  • mailto
  • news

RELATIVE URL

It is the webpage’s partial address. The protocol and server part are removed from the relative URL.

Mostly used in internal purpose i.e. creating links to the file that comes under same website as the WebPages on which you are placing the link.

Consider, a link of an image on wisdomjobs.com/internet_technology/internet_referemce_models, we can use the relative URL which can take the form like /internet_technologies/internet-osi_model.jpg.

Difference between Absolute and Relative URL

Absolute URL

Relative URL

Used to link web pages on different websites

Used to link web pages within the same website.

Difficult to manage.

Easy to Manage

Changes when the server name or directory name changes

Remains same even of we change the server name or directory name.

Take time to access

Comparatively faster to access.

Domain Name System Architecture

The Architecture consists Domain Names, Domain Name Space, Name Server that have been described below:

Domain Names

It is the string symbolizing an IP address. Some general domain names are com, edu, gov, net etc, where some country level names are au, in, za etc.

Below table shows the Generic Top-Level Domain names:

Domain Name

Meaning

Com

Commercial business

Edu

Education

Gov

U.S. government agency

Int

International entity

Mil

U.S. military

Net

Networking organization

Org

Non profit organization

Below table shows the Country top-level domain names:

Domain Name

Meaning

au

Australia

in

India

cl

Chile

fr

France

us

United States

za

South Africa

uk

United Kingdom

jp

Japan

es

Spain

de

Germany

ca

Canada

ee

Estonia

hk

Hong Kong

Domain Name Space

DNS refers a hierarchy in the internet naming structure which has multiple levels from 1 to 127 with a root at the top. Below is the DNS hierarchy diagram.

internet_technologies_tutorial

From the diagram, we can observe that each domain is divided into sub domains and can be divided further and so on.

Name Server

A DNS server has DNS database containing many names and their corresponding IP addresses. Since DNS database is huge, a single server is not sufficient. Hence, the data is distributed among many DNS servers.

  • Hierarchy of server is same as hierarchy of names.
  • The entire name space is segregated into the zones

Zones

It is the collection of nodes (sub domains) under the main one. Every zone is maintained by a server with database called zone file.

internet_technologies_tutorial

If the domain is not divided into sub domains, then both domain and zone are same.

Original server has reference to the lower level servers which has the information about the nodes in the sub domain.

TYPES OF NAME SERVERS

Below are the Name Servers categories managing the entire DNS.

  • Root Server
  • Primary Server
  • Secondary Server

ROOT SERVER

It is the Top level server containing entire DNS tree. It delegates the authority to the other server but does not have any information about domains.

PRIMARY SERVERS

This server stores a file related to its zone. It creates, maintains, and updates the zone file.

SECONDARY SERVER

This server transfers the data from one server to another server regarding a zone. It does not have authority to create or update a zone file.

DNS Working

Below is the process involved in the domain resolution.

When we type www.wisdomjobs.com into the browser, it asks the local DNS Server for its IP address.

Here the ISP has the local DNS.

  • If the local DNS cannot find the IP address of the requested domain name, the request is forwarded to the root DNS server and search over there.
  • The root DNS server replies with delegation that I do not know the IP address of www.wisdomjobs.com but know the IP address of DNS Server.
  • Then the local DNS server asks the com DNS server regarding the same.
  • Even the com DNS server replies the same that it knows the address of wisdomjobs.com but not the IP address of www.wisdomjobs.com.
  • Then the local DNS asks the wisdomjobs.com DNS server the same question.

Thereafter, wisdomjobs.com DNS server responds back with IP address of www.wisdomjobs.com.

Now, the local DNS sends the IP address of www.wisdomjobs.com to the computer that sends the request.

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