The Network

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Internet, the Information super highway. Nowadays, we are depending up on internet for each and everything. Whether you want to find the latest financial news, browse through library catalogs, exchange information with colleagues, or join in a lively political debate, the Internet is the tool that will take you beyond telephones, faxes, and isolated computers to a burgeoning networked information frontier. Internet populations is growing exponentially.

Just rewind a little bit. It all started with a Computer Network; 2 interconnected computers. Computer Network is the core of digital communication. But what is network? How does it work? Lets find out.

What is a Network?

Simply, a computer network is a set of computers connected together for the purpose of sharing resources and information.

Using network people can communicate with each other across the world at very low cost using services like chat and email. It can be used to transfer files and information between  devices at a very high speed.

A single software can be installed on the server and all the clients in the network can use it instead of installing it on every individual PCs,  reducing the cost of software. Devices like printers, scanners and other hardwares can be shared easily.

From Little Drops To the Mighty Ocean

Depending up on the size, there are maily 3 types of network. – LAN, MAN and WAN
LAN
Local Area Network or LAN is a network that is confined to a very small area. It is generally limited to a building. LAN networks are easy to establish using inexpensive devices like routers, switches and hubs.
MAN
Metropolitan Area Network or MAN connects different LANs together and it covers larger geographic areas, such as cities.
WAN
 Wide Area Networks or WAN connects larger geographic areas, such as countries and continents.
The Internet is the best example of a public WAN.
In a building, there may be so many devices like laptops, desktops and mobile phones connected to each other. This can be called as a LAN. Nodes are usually connected by means of ethernet cable or WIFI.
When these LANs are connected to each other, it is  called a MAN. They are connected to each other using coaxial cables or optical fibers.
WAN connects different MANs together and form a Wider Network. They are connected to each other by means of satellite or transoceanic cables.

Hello.. Who is it?

Every machine on the the network has a unique number assigned to it, called an IP address.
An IP address is similar to your phone number. Your phone number is a unique set of numbers that identifies your phone so that other people can call you. Similarly, an IP address is a unique set of numbers that identifies your computer so that it can send and receive data with other computers.
IP address is a 32 bit unique value.
It is a numerical value combining 4, 8 bit binary digits or octets separated by dots that looks some what like this.
00001010.00001001.00000000.00011001

For our convenience we convert binary to decimal 

10.9.0.25
IP Address value ranges from
      0  .  0  .  0  .  0   (00000000.00000000.00000000.00000000)
    255.255.255.255  (11111111 . 11111111 . 11111111 . 11111111)
There are mainly Two Types of IP address – Public IP and Private IP

Public IP address is an IP address that can be accessed over the Internet.
This IP address is unique throughout the internet. 
Private IP address are addresses that are assigned to computers within your private network or LAN.
This IP address is unique to a network. Private IP addresses are not  directly exposed to the Internet.
That means we cannot access any device outside our LAN using its private IP address.

Classes Of IP Address

Ip address have different classes. The class of the ip address is decided by the first octet
.
For Practical purposes we will use only Class A, B and C.
Every IP address has Two parts – one is the network part and the other is the host part.
The network mask help us to identify which part of ip address is the network part and which part is the host part. In most cases, network mask is decided by the class of the IP address

For Example consider the IP
10.9.0.25 (Dotted Decimal )
00001010.00001001.00000000.00011001 (Dotted Binary)
In a network mask, all the bits in the network part will be 1 and host part will be 0.

In Class A IP address first octet denotes the network part and remaining 3 will be host part.
In Class B IP address first two octet denotes the network part and remaining two will be host part.
In Class A IP address first three octet denotes the network part and remaining will be host part.

Since it is a class A IP address, first octets will be 1s. So Subnet mask will be
11111111.00000000.00000000.00000000
Or 255.0.0.0

So How Does It Work?

LAN, WAN, Public IP, Private IP okay fine.. How do they work together?
Well, this is how our internet connection work.
If we want internet connection in our home, we contact an ISP. ISP or Internet Service Provider is an Organization that provides us access to the internet. For example Asianet , BSNL etc. ISP gives us an IP address which can be used for accessing the internet. Modem simply demodulates the incoming packets and modulates the outgoing packets. If we have a single PC, we can directly connect modem to that PC.
If we have multiple devices within our home we will have to use a router.

Router is a device which is used for connecting two networks together. Router creates a private network and assign private IP to all our devices. Here, our router get the public IP address from the ISP, and each of the devices connected to our router get a private IP. These private IPs will be mapped to the public IP using technique called NAT. 

Internet

Internet is a world wide system of networks consisting of thousands of smaller network. The Internet is the hardware part used for transporting data. – it is a collection of computer networks connected through either copper wires, fiber-optic cables or wireless connections.

World Wide Web

WWW can be termed as the software part that helps us to use that data – it is a collection of web pages connected through hyperlinks and URLs. The World Wide Web is one of the services provided by the Internet.
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