Communication

History of Computer Network

Today's computer network is the Internet communication network 60 in this field in the early telephone network was a trace at the beginning of World authority. Internet World is the source of the advanced research network (ARPANET) of the U.S. Defense Department was in 1969. Things to see of growth in the last 35 year of the computer network. 
In 1974 Ethernet was to be verified at the Xerox PARC Alto computer network. And after in 1978 the modem dial up connection was being introduced 
after 1978 in 1981 – the new TCP /, UNIX operating system was being released of the IP suite. The first portable computer and it was promoted in size of almost a pound suitcase 
In 1981, PC are being promoted from IBM and after that in 1982 TCP / IP (Transmission Control Protocol and Internet Protocol) were created for normal ARPANET And in the TCP was used to regulate the ARPANET / IP protocol which was taken up by Pentagon. 
In 1986 the protocol TCP / IP were to be introduced with the new Compaq workstation PC and in 1987 the network host break had crossed almost 100000 and in 1989 it crossed the host almost 1000000 and in 1990 the ARPANET was being stopped and many other tools like Gopher were being introduced in 1991 the ARPANET was being changed to NFSnet as the major government network linking research institution and NFSnet was being advance to T3 and even the world wide web was being developed and directed by lee and the CERN acted as the first main web server in 1991.
By 1992 the internet was very familiar worldwide to everyone in the form of www.

Component of Computer Network

There are five component in a computer network.

• Message:- Message is consist of information that a user of computer network wants to transmit it to the other computer in the network.it may be Text, Image, Video or Audio.

• Sender:- Sender is the device which send the message . It may be a computer, smartphone, workstation or video camera.

• Receiver:- Receiver is the device that receive the massage. It may be a Radio, T.v, Computer, smartphone or printer.

• Transmission medium:- Transmission medium is a physical by which a message flow from sender to receiver. It may be wired or wireless eg. radio wave, micro wave, twisted pair wire co axial cable or fiber optics.

• Protocol:- A Protocol is set of rule that governs the data communication. Protocol is the most essential part of computer network. Without protocol two computer can be connected but they can not communicate to each other.

Data Flow

There are three types of Data flow in a computer network.

1. Simplex mode:- In this mode the data can flow in only one direction. The sender never play the role of receiver and receiver never play the role of sender. eg. Keyboard, Mouse, radio , television are the examples of the simplex data flow.
2. Half Duplex:- Data can flow in either direction --from sender to receiver or receiver to sender but only in one direction at a time. eg. Walky-talky, Fax machine, ATM.
3. Full Duplex:- Data can Flow either direction --from sender to receiver and receiver to sender simultaneously. 

Types of Connection

In a network two or more devices are connected through links.There are two possible way to connect the devices they are follow:-

1. Point-to-Point connection:- A point to point connection provide a dedicated link between two devices as shown in figure

2. Multipoint connection:- A multipoint connection also called multidrop connection. In such a communication more than two devices share a single link as shown in figure. In the multipoint connection the channel capacity is sheared. If many devices share the link simultaneously, it is called spatically shared connection but if user share the link turn  by turn than it is time sharing connection.