This document provides an introduction to networking and data communication. It discusses key topics such as: - Data communication is the transmission of data over a communications channel between devices. A network connects computing devices to communicate and share resources either physically or wirelessly. - Data must be converted into signals to be transmitted over physical or wireless media. Signals can be analog or digital. - Common network topologies include mesh, bus, ring and star configurations. Hybrid topologies combine elements of different topologies. - Transmission media can be guided (using cables) or unguided (wireless) and include technologies like twisted pair, coaxial, fiber optic, radio waves, microwaves and infrared.

1. INTRODUCTION TO NETWORKING
AND
DATA COMMUNICATION
S.N. MBURU - SCI

2. INTRODUCTION
TO DATA COMMUNICATION &
NETWORKS

3. Introduction to networking data
communication
 Data communication is the transmission of data and
information over a communications channel between
two devices
 Communications between computers can be as
simple as cabling two computers to the same printer.
It can be as complex as a computer at NASA sending
messages through an elaborate system of relays and
satellites as shown by the animation in the next slide.
 A network is collection of computing devices connected
in order to communicate and share resources.
Connections between the devices can be physical using
wires or cables or wireless using radio waves or infrared
signals
.

4. Communication systems

5. Data and data signals
 Data/ information are entities that convey meaning within
a computer or computer system. In data communication,
the two terms means the same.
 Data can be transmitted over physical or wireless media.
To be transmitted it must first be converted into a signal.
 Signals are the electric or electromagnetic encoding of
data and are used to transmit data. signals can be
analog or digital.
 Data Signals can be analog or digital. Analog signals
have an infinite number of values in a range represented
using sine wave while digital signal is discrete,
discontinuous voltage pulses represented using square
wave

6. Analog signal

7. Digital signal

8. Forms of information
 Familiar forms of information carried by data
communication are:
 Text: Alphabetic characters
 Numeric data: Information in the form of numbers,
 Graphical data: In the form of pictures or diagram
that can be sent by fax machines or computers.
 Sound:
 Video: Pictures accompanied by sound.
 Multimedia: A combination of the different text,
video and sound.

9. Channel
 A communications channel, also called a
communications line or link, is the path that
the data follows as it is transmitted from one
computer to another
 Any communications channel has a direction
associated with it as shown below.

10. Channels types

11. DTE and DCE
Data Terminal Equipment (DTE): Sources or
destinations of information. Comprises of
communications equipment such as terminals, host
computer, printer etc.
Data Circuit Terminating Equipment (DCE): Made up
of interface devices such as the modem, switches,
routers etc.
Mediu
m
DT DC DC DT
E E E E
Sourc Interfa Sour Destinati
e ce ce on

12. Data communications
interfacing

13. Illustration of DTE-DCE setup
DTE-computer DCE-modems DTE-computer

14. Types of networks
 LAN (Local Area Network)Network in small
geographical Area (Room, Building or a
Campus)
 MAN (Metropolitan Area Network)Network in
a City
 WAN (Wide Area Network) Network spread
geographically (Country or across Globe)

15. Benefits of Networks
Resource Sharing
 Hardware (computing resources, disks, printers)
 Software (application software)
Information Sharing
 Easy accessibility from anywhere (files, databases)
 Search Capability (WWW)
Communication
 Email
 Message broadcast
 Remote computing

16. Networks topologies
 Computer network Topology refers to the
physical layout of the network devices and
cabling and how all the components
communicate with each other. There are
four basic types of computer network
topologies:
 mesh,
 bus,
 ring,
 star

17. Common Topologies
 Physical layout of network devices
 Four types: mesh, bus, ring, and star
Lesson 3—Networking BASICS 17

18. Mesh Topology
 A mesh topology is also called a point-to-
point topology.
 Each device is connected directly to all
other devices on the network.
 A mesh topology is sometimes used in a
wide area network (WAN) setting to
ensure that all the sites continue to
transmit in the event of a cable failure or
another similar problem.
 Mesh topologies are rarely used in a LAN.
Lesson 3—Networking BASICS 18

19. Mesh Topology
Lesson 3—Networking BASICS 19

20. Bus Topology
 The most common type of multipoint
topology is a bus topology.
 A computer network bus topology is
characterized by one starting point and
one ending point.
 A bus network topology works well for
smaller networks and is inexpensive to
install.
 However, it can become slow when more
devices are added to the network
Lesson 3—Networking BASICS 20

21. Bus Topology
Lesson 3—Networking BASICS 21

22. Ring Topology
 It is a circular with no ends.
 Packets are sent from one device to the
next.
 It does not slow down as more devices are
added.
Lesson 3—Networking BASICS 22

23. Ring Topology
Lesson 3—Networking BASICS 23

24. Star Topology
 A star topology describes a network in which all
the devices are connected to a central device
known as a hub, which is responsible for
receiving and forwarding packets to other
devices on the network.
 Because everything is centralized in a star
topology, it is the easiest topology to manage
and troubleshoot
Lesson 3—Networking BASICS 24

25. Star Topology
Lesson 3—Networking BASICS 25

26. Hybrid Topologies
 They are variations of two or more topologies.
 Star bus – used to connect multiple hubs in a
star topology with a bus.
 Star ring – wired like star, but functions like a
ring.
Lesson 3—Networking BASICS 26

27. Transmission Media
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

28. Data transmission
• A communication link is established by using
physical or wireless medium. In most cases it
is a pair of electric conductors, fiber optic
cables or using electromagnetic waves on the
free space.
• Thus media are roughly grouped into guided
or unguided media.

29. Classes of transmission media

30. GUIDED MEDIA
Guided media, are those that provide a conduit (physical
connection) from one device to another, include twisted-
pair cable, coaxial cable, and fiber-optic cable.
Three categories of guided media
Twisted-Pair Cable
Coaxial Cable
Fiber-Optic Cable

31. Twisted Pair Cables
• The oldest and still most common transmission
medium is twisted pair.
• Consists of two insulated copper wires twisted
together.
• Can be used for either analog or digital
transmission.
• Twisting reduces the effects of the external
interferences.
• Common applications are the telephone system
and Local Area Network of computers.

32. Unshielded Twisted Pair (UTP) Cables
• The commonly used UTP cables are
categorized as CAT 3, CAT 5 and CAT 5e.

33. Coaxial Cables
• The construction and shielding of the coaxial
cable give it a good combination of high
bandwidth and noise immunity.
• The energy loss due to skin effect is also
minimized.

34. Coaxial Cable
Center
conductor
Dielectric Braided
material Outer
outer cover
conducto
r
Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks Figure 3.39

35. Optical fiber
• A unidirectional optical transmission system
has three components ; light source,
transmission medium and detector.
• The light source works such that a pulse of
light indicates “1” and absence of light
indicates “0”.
• The detector at the receiving end generates an
electric pulse when light falls on it.

36. Optical Transmission Ctd.
• Optical Transmission is based on the theoretical
principle called Total Internal Reflection in
physics.
Light Source
Total Internal Reflection
• A light ray incident at or above the critical
angle is trapped inside the fiber.

37. Fibre cable structure
Core -- a very narrow strand of high quality glass.
Cladding -- again, made from high quality glass,
with a slightly different index of refraction of the
core.
Buffer/outer jacket -- usually constructed from
plastic

38. Figure 7.14 Fiber construction

39. Comparison of Fibre Optics & Copper Wire
•Fiber has many advantages.
• Higher Bandwidth
• Low attenuation
• Not affected by electromagnetic
interferences.
• Not affected by corrosive chemicals.
• Lighter in weight
• Secured from wiretappers.
•Do not induce high voltages when
lightening takes place.

40. UNGUIDED MEDIA: WIRELESS
Unguided media transport electromagnetic waves
without using a physical conductor. This type of
communication is often referred to as wireless
communication.
Topics discussed in this section:
Radio Waves
Microwaves
Infrared

41. Figure 7.19 Wireless transmission waves

42. Broadcast Radio
 Description of broadcast radio antennas
 Omnidirectional
 Antennas not required to be dish-shaped
 Antennas need not be rigidly mounted to a precise
alignment
 Applications
 VHF and part of the UHF band; 30 MHZ to 1GHz
 Covers FM radio and UHF and VHF television
 Cellular telephony
 Wireless LANs

43. Microwaves
• Above 100MHz, the waves travel in straight
lines and can therefore be narrowly focused.
• Parabolic antennas are used.
• Microwaves do not pass through buildings
well.
• Used to establish links when laying physical
cables are very expensive or impracticable.
• Satellite communications.

44. Figure 7.21 Unidirectional antennas

45. Terrestrial Microwave
 Parabolic dish
 Narrow beam – line of sight on towers to avoid obstacles
 Series of towers for long distance
 Applications:
 Long haul telephone
 Voice and TV
 Short point to point between buildings
 Main Source of loss
 Attentuation – especially with rainful
 Repeaters or amplifiers 10 to 100km
 Interference with overlapping bands

46. Satellite Microwave
 It is essentially a microwave relay station
 Uplink
 Receives transmission on one frequency
 Downlink
 Transmits on a second frequency
 Operates on a number of frequency bands known as
transponders
 Point to Point
 Ground station to satellite to ground station
 Multipoint
 Ground station to satellite to multiple receiving stations

48. Infrared
 Description of broadcast radio antennas
 Transmitters/receivers (transceivers) modulate non-
coherent infrared light
 Transceivers must be within line-of-sight of each other
either directly or via reflection
 Unlike microwave, infrared does not penetrate walls
 Applications
 Small LANs
 Short point-to-point connections