Computer Network
Computer Network
A computer network is interconnection of various computer systems located at
different places. In computer network two or more computers are linked together
with a medium and data communication devices for the purpose of
communication data and sharing resources. The computer that provides
resources to other computers on a network is known as server. In the network
the individual computers, which access shared network resources, are known as
nodes.
Types of Networks
Local-Area Networks (LANs)
The computers are geographically close together (that is, in the same building).
Wide-Area Networks (WANs)
The computers are farther apart and are connected by telephone lines or
radio waves. The following characteristics are also used to
categorize different types of networks.
- Topology
The geometric arrangement of a computer system. Common topologies include bus, star, and ring.
- Protocol
The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called Ethernet. Another popular LAN protocol for PCs is the IBM token-ring network.
- Architecture
Networks can be broadly classified as using either peer-to-peer or client/server architecture. Computers on a network are sometimes called nodes. Computers and devices that allocate resources for a network are called servers.
- Local Area Network (LAN)
LAN is a computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANS over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN).
Data Transmission Modes
Data Transmission Modes
There are three ways for transmitting data from one point to another.
1. Simplex : In simplex mode the communication can take place in one
direction. The receiver receives the signal from the transmitting device.
In this mode the flow of information is Uni-directional. Hence it is rarely
used for data communication.
2. Half-duplex : In half-duplex mode the communication channel is used
in both directions, but only in one direction at a time. Thus a half-duplex
line can alternately send and receive data.
3. Full-duplex : In full duplex the communication channel is used in both
directions at the same time. Use of full-duplex line improves the
efficiency as the line turnaround time required in half-duplex arrangement
is eliminated. Example of this mode of transmission is the telephone
line.
Communication and Networking
Data Communication
We all are acquainted with some sorts of communication in our day to day life.
For communication of information and messages we use telephone and postal
communication systems. Similarly data and information from one computer
system can be transmitted to other systems across geographical areas. Thus data
transmission is the movement of information using some standard methods.
These methods include electrical signals carried along a conductor, optical
signals along an optical fibers and electromagnetic areas.
Basic Elements of a Communication System
The following are the basic requirements for working of a communication
system.
1. The sender (source) who creates the message to be transmitted
2. A medium that carries the message
3. The receiver (sink) who receives the message
In data communication four basic terms are frequently used. They are:
Data : A collection of facts in raw forms that become information after processing.
Signals : Electric or electromagnetic encoding of data.
Signaling : Propagation of signals across a communication medium.
Transmission : Communication of data achieved by the processing of signals.
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