The act of transferring data and information at a far distance for communication is called telecommunication.

The transmission of data from a place to another using computer technology is called data communication.

The interconnection of two or more computers by means of transmission media like cable or without cables in order to communicate and share resources data, application software, and hardware is known as a computer network. Its advantages are:

1. Hardware sharing.
2. Data and software sharing.
3. Transfering and communication facilities.
4. Security and reliability.
5. Sharing the resources remove its cost or reduce the cost.
   

A computer network is the interconnection of computers to share the data, files, hardware, software, and so on. It also makes the communication and transmission reliable In the offices, the files should be transferred from one to other branches very often. Also, the software and hardware can be shared which reduces the cost of buying many items of hardware, software, and so on. So, computer network reduces expenses of offices.

The reasons for keeping the computers on the network are:

1. To share hardware resources.
2. To share the application software, data, files, and so on.
3. To make communication and transmission reliable.
4. To reduce the expenses of computer accessories.

In a network of computers, many computers are connected toeach other at a distance for the sharing of information,data, software, hardware and so on. Computer networkhas made the communication and transmission easier,faster, reliable and secure. The information in one cornerof world can spread whole over the world in short periodthrough computer network. We feel like working in aroom though we are working a kilometers awayto eachother in a computer network. So, computer networkmake the world...

The essential components of simple network are:
- Server.
- Workstation/clients.
- Network Interface unit.
- Communication Channel on Transmission Media.

The differences between server and workstation are:

Server	Workstation
It is the main component of the computer network that controls, store and distribute the data, programs, etc.	It is the computer besides server in a network that uses the available resources in a network.
It provides the facilities of sharing hardware, data, software and so on.	It shares and transfers the data, programs, etc. among clients and servers under servers permission.

The differences between dedicated server and non-dedicated server are:

Dedicated server	Non-dedicated server
It can be used as server and workstation both.	It can only be used as server.
It is designed as server of simple and small computer network.	It is designed as a server of specific and advanced network.

Thepath through which data, information and othervarious form of files transfers on a network in theform of electromagnetic wave is called communicationchannels.
Its types are:
- Bounded transmission media.
- Unbounded transmission media.

The bounded transmission media used in computernetwork are:
- Twisted Pair Cable:
i.Unshielded Twisted pair.
ii.Shielded Toasted pair.
- Coaxial cable.
- Fiber optic cable.

The importances of modem in computer network are:
- It enables to transmit data, information and files.
- It converts digital signal into analog form and alsoits vice versa.
- It requests and loads the internet facilities.
- It enables to share hardware andsoftware resources.

The different types of computer network based on range are:
-LAN (within a buildingor room)
-MAN (within metropolitialarea)
-WAN (within global or wide area)

The interconnection of few computers with cables orsmall wireless media within a building vizsmall territory for the sharing of hardware and softwareresources is called LAN.
It is the basic unit of computer network. It isconnected with cables within a small area. So, it hashigh data transmission speed. Also, wireless media isalso used in LAN.

The computer network that connects two or more LAN inthe metropolitialarea with wireless communication channelfor the sharing of hardware and softwareresources iscalled MAN.
There are large number of LAN connectedto each otherunder MAN. It is ownedby single of multipleorganizations.It is the network biggerthan LAN but smaller than WAN.

The global computer network that spreads over a largegeographic area with unguided or wirelessmedia forthe purpose of communication, transmission and share iscalled MAN.
It connects the many groups of LANS and MANs. Ituses the wireless transmission medialike microwave,radio save or satellite links. Data can be transmittedat the speed of 10 giga bits per second ( Gbps ) in thesenetwork.

The differences between LAN & WAN are:

LAN	WAN
It is interconnection of computers within a small area.	It is interconnection of LANs and MANs within a global area.
Both wired and wireless media is used as transmission media.	Highly powerful wireless media is used as transmission media.

We all know that, WAN is the networks that spreads overthe global world. There are many small computer networksin the world. LAN is the smallest and unit computer network.MAN spreads over metropolitial area and connects multipleLANs. And finally, many MANs in the world are connected to each other and WAN is formed. So, a WAN is composedof LANS and MANs.

The difference between client-server model and peer-to-peermodel are:

Client-server	Peer-to-peer
It is also called domain model.	It is also called workgroup model.
It has a server and the workstations.	All the computers in network works as server and workstation both.
Server decides for sharing of resources.	Each computer uses decide for sharing of resources.

The manner in which the computers on a network areconnected with the help of transmission media iscalled network topology.
It's basic types are:
-Bus topology.
- Ring topology.
-Star topology.
- Mesh topology.

The topology in which computer are arranged in alinear format and the nodes (computer)are connecteddirectly to the common cable with the help of T-connectorsis called bus topology.
The common cable is also known as a network busor trunk that acts as a backbone to a network. Manydifferent lengths of co-axial cables are used in this type oftopology. When any nodes sends data, the data passes on bothdirections in the form of packets through the bus andreach to all the nodes.

The advantages of bus topology are:
- It iseasy to setup the nodes.
- It requires less amount of cables.
- It uses the co-axial cables which is cheap & easy to setup.
- Failure of any nodes doesn't effect other nodes on thenetwork.

Thedisadvantages of Bus topology are:
- If the bus has problem, whole network fails to function.
- It provide limited flexibility to change the position of nodes.
- It will be more weaker with theincrementof nodes.
- This topology doesn'tworks for huge network.

Ring topology in a computer network is the pattern of nodes where the nodes are arrangedin the shape of ring(circle).
In thistopology,both ends of cable is connected tothe nodes which removes the necessities of terminator.Co-axial cables are connected among the node in circleshape. Every nodes acts as a repeater on the network thatboasts the signals before passing it to other.

Theadvantages ofring topology are:
- Network signals are strong as every nodes acts asrepeater.
- It supports high data transmissionrate.
- It is easy to setup
- It requires less cables for setup.
The disadvantages ofring topology are:
-Failure of any node breaks the whole function.
- The diagnosisof the fault is difficult.
-Data transmission is slow in case of huge network.
- It isuneasy to add and remove the nodes.

Hub is a networking device having the series of connecting ports which joins multiple nodes orother network devices together to form the segment of computer network.
The difference of switch and hub are:

Switch	Hub
It transmits the shared resources to assigned MAC address on a network.	It transmits the shared resources to all the node on the network.
It has better performance than hub as it follow only the assigned path.	It has weaker performance than switch as it flow the data in...

The topology in which all the nodes are connectedthrougha centrally located device in the form of staris called star topology.
However, the nodes are not under compulsionto bearrangedin the form of star but should be directlyconnected with the network connecting device. It is connectedby either switch or hub. The sent data from any nodesfirst reach to the switch or hub andto the assigned MACaddress (nodes).

The advantages of stars topology are:
-Its easy to remove and add the nodes.
-Failure ofanynodesdoesn'taffect other nodes.
-Fault detection is easy.
- It is suitable for a huge network which is alsoreliable.
The disadvantages of stars topology are:
-It requiresmore cables for installation.
-Failure of hub or switch creates entire network failure.
- It is expansive to arrange this topology.
- It has the chance of data loss.

Communication protocol is a programthat controls andmanages the transferringof data or message from onecomputer to other on a network.
Any four of them are:
-TCP/IP (Transmission control Protocol/Internet Protocol)
- SMTP (simple Mail Transfer Protocol)
- FTP (File Transfer Protocol)
- HTTP (Hypertext transferProtocol)
-POP (Post office protocol)
- IPX/SPX (Internet Package Exchange/Sequential PacketExchange)
- NETBEUI (Net Bios Extended User Interface)

FTP: File Transfer Protocol
SMIP: Simple Mail Transfer Protocol
TCP/IP: Transmission Control Protocol/Internet Protocol
ISP: Internet Service Provider
POP: Post Office Protocol
UPT: Unshielded Twisted Pair
STP: Shielded Twisted Pair
NetBEUI: Net BIOS Extended User Interface
DARPA: Defense Advanced Research Projects Agencies
HTTP: Hyper Text Transfer Protocol
MODEM: Modulator and Demodulator
WLAN: Wireless Local Area Network