2. Data communication
Data communication technologies deal with
means and methods of data transfer from
one location to another. Marriage between
computing and data communication
technologies is one of the most exciting
developments that has revolutionized
information age. This development gave
birth to computer network.
Second slide 2
3. COMPUTER NETWORKS
A computer network is a network of computers that are
geographically distributed, but connected in a manner
to enable meaningful transmission and exchange of
data among them.
3
Third slide
4. TYPES OF COMPUTER NETWORKS
Based on characteristics such as geographic
distribution of nodes, data rate, error rate,
communication link, ownership, and
communication cost, networks are classified
broadly into two types:
LAN AND WAN.
Networks that share some of the characteristics of
both LANs and WANs are sometimes refered to as
MANs.
Fourth slide 4
5. LAN
A lan connects computers located near each other. In
some cases “local” means within the same room or
building. In other cases “local” refers to computers
located several miles apart.
WAN
In contrast WAN consists of computers in different cities,
states or even countries. We can refer to WAN as long-haul
networks because of the great distance the information they
exchange must travel.
Fifth slide 5
6. A sender (source) that creates and sends a
message.
A medium that carries the message.
A receiver (sink) that receives the message.
Sixth slide
6
7. Basic elements of communication system are
graphically shown here.
Basic elements of any communication system are shown in this
figure:
SENDER MEDIUM RECEIVER
(SOURCE) Carries message (SINK)
SEVENTH SLIDE 7
8. Data transmission modes
Three modes of data transmission are:
simplex Half- Full-
duplex duplex
EIGHTTH SLIDE 8
9. There are three modes of data transmission. These are
simplex
Half-duplex
Full-duplex
simplex: A simplex communication system can transmit data
in one direction only. Devices connected to such a circuit are
either send only(such as keyboard) or receive only (as printer). As
in figure below
sender simplex receiver
9
10. HALF-DUPLEX
A half-duplex communication system can transmit
data in both directions, but in only one direction only at a
time. Hence it can alternately send and receive data. Example
is wireless set.
Sender Sender
or or
receiver receiver
Half duplex 10
11. FULL-DUPLEX
A full-duplex system needs to switch direction each
time the direction of data transfer reverses. A full-duplex
communication system allows data to flow in both the
directions simultaneously.
Sender Receiver
And And
receiver Sender
Full-duplex
11
ELEVENTH SLIDE
12. DATA TRANSMISSION MEDIA
There are several types of physical channels (communication
media) through which data can be transmitted from one point
to another. Some of the most commonly used data
transmission media are
Twisted pair wire (UTP cable).
Coaxial cable.
Microwave system.
Communication satellite.
Optical fibres.
TWELVETH SLIDE 12
13. NETWORK TOPOLOGIES
Network topology refers to a network shape or geometic
arrangement of computers. Topology gives a way to compare and
classify different networks. Choice of a topology for a computer
network depends on a combination of factors such as:
Desired performance of the system.
Desired realiability of the system.
Size of the system.
Expandability of the system.
Availability of communication lines.
THIRTEENTH SLIDE 13
