Computer
Awareness Notes: Networking (Part 1)
Dear Aspirants,
Welcome to Mentor for Bank Exams. Here we are sharing
the study material on Computer Networking, that will help
you succeed in Bank, Insurance and oter competitive Exams.
Introduction:
Computer Networks means interconnected set of
autonomous system that permit distributed processing to information.
Basic Elements of a Communication System
The following are the
basic requirements for working of a communication system.
- A sender (source)
which creates the message to be transmitted.
- A medium that
carries the message.
- A receiver (sink)
which receives the message.
In data communication four basic terms are frequently used.
- 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.
Characteristics of Networking:
- Topology: The geometrical arrangement of
the computers or nodes.
- Protocols: How they communicate.
- Medium: Through which medium.
Basic Types of Networks:
Mainly three
types of network based on their coverage areas: LAN, MAN,
and WAN.
- LAN (Local Area
Network): LAN
is privately owned network within a single building or campus.A local area
network is relatively smaller and privately owned network with the maximum
span of 10 km.
- MAN
(Metropolitan Area Network): MAN is defined for less than 50 Km and
provides regional connectivity within a campus or small geographical
area. An example of MAN is cable television network in city. A
MAN can be owned by a private company or it may be a service provided by a
public company such as local telephone company. Telephone companies
provide a popular MAN service called (SMDS) Switched Multi-megabit Data
Services.
- WAN (Wide Area
Network): A
wide Area Network (WAN) is a group Communication Technology ,provides no
limit of distance. A wide area network or WAN spans a large
geographical area often a country. The Internet is a system of linked
networks that are world wide in scope and facilitate data communication
services such as remote login, file transfer, electronic mail, World Wide
Web and newsgroups etc.
Network Topology
Network topology is the
arrangement of the various elements of a computer or biological network.
Essentially it is the topological structure of a network, and may be depicted
physically or logically.
The common network
topologies include the following sections
- Bus Topology: Each node is directly connected
to a common cable.
- Star Topology: Each node has a dedicated set of
wires connecting it to a central network hub. Since, all traffic passes
through' the hub, it becomes a central point for isolating network
problems and gathering network statistics.
- Ring Topology: It is logically closed
loop. Data packets travel in a single direction around the ring from one
network device to the next. Each network device acts as a repeater to keep
the signal strong enough as it travels.
- Mesh Topology: Each system is connected to all
other systems in the network.
o In bus topology at the first, the
message will go through the bus then one user can communicate with other.
o In star topology, first the message
will go to the hub then that message will go to other user.
o In ring topology, user can
communicate as randomly.
o In mesh topology, any user can
directly communicate with other users.
- Tree Topology: In this type of network
topology, in which a central root is connected to two or more nodes that
are one level lower in hierarchy.
Data Transmission Modes
There are three
ways for transmitting data from one point to another:
- 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.
- 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.
- 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
turn-around time required in half-duplex arrangement is eliminated.
Example of this mode of transmission is the telephone line.
Digital and Analog Transmission:
Data is transmitted from
one point to another point by means of electrical signals that may be in digital and analog form.
- In analog signal the
transmission power varies over a continuous range with respect to sound,
light and radio waves. Analog signal is measured in Volts and its
frequency in Hertz (Hz).
- A digital signal may
assume only discrete set of values within a given range.
- When digital data are to be sent
over an analog form the digital signal must be converted to analog form.
So the technique by which a digital signal is converted to analog form is
known as modulation and the reverse process, that is the conversion of
analog signal to its digital form, is known as demodulation.
The device, which converts digital signal into analog, and the
reverse, is known as modem.
