This document provides an overview of computer fundamentals and data communication concepts including: 1) The basic elements of a communication system including the medium, sender, receiver, and message. 2) Types of transmission modes and data transmission speeds. 3) Common data transmission media such as twisted-pair wire, coaxial cable, microwave systems, satellites, and optical fibers. 4) Network topologies including star, ring, bus, and hybrid networks. 5) Communication protocols and the OSI model for standardizing network communication.

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Ref. Page Data Communications and Computer Networks
Data Communications and Computer
Networks
Computer Fundamentals
Professor Dr. Md. Ismail Jabiullah
Department of CSE
Daffodil International University

2. Learning Objectives
In
•
•
this chapter you will learn about:
Basic elements of a communication system
Techniques, channels, and devices used to transmit
data between distant locations
Types of computer networks
Communication protocols and their use in computer
networks
Internetworking tools and their use in building large
computer networks
Characteristics and advantages of distributed data
processing
•
•
•
•
Ref. Page 320 Data Communications and Computer Networks Slide 2/36

3. Communication
Basic Elements
System
of a
Medium
Carries the message
Receives the
Creates and sends
message
a message
Ref. Page 321 Data Communications and Computer Networks Slide 3/36
Receiver
(sink)
Sender
(source)

4. Transmission Modes
Data
(a) Simplex
OR
(b) Half-duplex
AND
(c) Full-duplex
Ref. Page 321 Data Communications and Computer Networks Slide 4/36
Receiver
(and Sender)
Sender
(and Receiver)
Receiver
(or Sender)
Sender
(or Receiver)
Receiver
Sender

5. Data Transmission Speed
• Bandwidth: Range of frequencies available for data
transmission. It refers to data transmission rate. Higher
the bandwidth, the more data it can
• Baud: Unit of measurement of data
transmit
transfer rate.
Measured in bits per second (bps)
Ref. Page 322 Data Communications and Computer Networks Slide 5/36

6. Data Transmission Speed Category
Narrowband: Sub-voice grade channels in range from
45 to 300 baud. Mainly used for telegraph lines and
low-speed terminals
Voiceband: Voice grade channels with speed up to
9600 baud. Mainly used for ordinary telephone voice
communication and slow I/O devices
•
•
Broadband: High speed channels with speed up to
million baud or more. Mainly used for high-speed
computer-to-computer communication or for
simultaneous transmission of data
1
•
Ref. Page 322 Data Communications and Computer Networks Slide 6/36

7. Data Transmission Media
The most commonly used ones
Twisted-pair wire (UTP cable)
Coaxial cable
Microwave system
are:
•
•
•
•
•
Communications satellite
Optical fibers
Ref. Page 323 Data Communications and Computer Networks Slide 7/36

8. Unshielded
Cable
Twisted-Pair (UTP)
Ref. Page 323 Data Communications and Computer Networks Slide 8/36

9. Coaxial Cable
Central copper wire
PVC insulation
Copper mesh
Outer PVC shield
Ref. Page 323 Data Communications and Computer Networks Slide 9/36

10. Microwave Communication System
Receiving
antennas
Transmitting antennas
In between
repeaters
Transmitting
station
Receiving
station
Line of sight Line of sight Line of sight
Ref. Page 324 Data Communications and Computer Networks Slide 10/36

11. Satellite Communication System
Satellite in space
6 GHz 4 GHz
Uplink Downlink
Receiving
station on earth
Transmitting
station on earth
Ref. Page 325 Data Communications and Computer Networks Slide 11/36

12. Optical Fiber Communication System
Optical fiber Electrical
signal
Electrical
signal
Amplifier
Receiver
Sender
Light waves
Ref. Page 326 Data Communications and Computer Networks Slide 12/36
Electrical to
light wave
converter
Light to
electrical wave
converter

13. Digital and Analog Data Transmission
• Analog signal: Transmitted power varies over a
continuous range. Example: sound, light, and radio
waves
• Digital signal: Sequence of voltage pulses represented
in binary form
• Computer
telephone
generated data signal is digital, whereas
lines carry analog signals
(Continued on next slide)
Ref. Page 327 Data Communications and Computer Networks Slide 13/36

14. Digital and Analog Data Transmission
(Continued from previous slide)
• When digital data is to be sent over an analog facility,
digital signals
• Conversion of
modulation
• Conversion of
demodulation
must be converted to analog form
digital signal to analog form is known as
analog signal to digital form is known as
• Digital transmission of data is preferred over analog
transmission
transmission
of data due to lower cost, higher
speeds, and lower error rate
Ref. Page 329 Data Communications and Computer Networks Slide 14/36

15. Analog and Digital Signals
Voltage
+v
t
0 1/f 2/f
-v
(a) Analog signal
v
1 1 1 1
0
t
(b) Digital signal
Ref. Page 328 Data Communications and Computer Networks Slide 15/36
0 0 0

16. Network Topologies
• Term network topology refers to the way in which
the nodes of a network are linked together
• Although number network topologies
four major ones are:
• Star network
• Ring network
• Completely connected network
are possible,
• Multi-access bus network
Ref. Page 338 Data Communications and Computer Networks Slide 16/36

17. Star Network
Host
Node
Ref. Page 339 Data Communications and Computer Networks Slide 17/36

18. Ring Network
Ref. Page 339 Data Communications and Computer Networks Slide 18/36

19. Completely Connected Network
Ref. Page 340 Data Communications and Computer Networks Slide 19/36

20. Multi-Access Bus Network
Computers (nodes)
Single communication line shared by all nodes
Ref. Page 341 Data Communications and Computer Networks Slide 20/36
e communication line shared by all

21. Hybrid Network
Completely
connected
Ring
Star
Ref. Page 341 Data Communications and Computer Networks Slide 21/36

22. Network Types
• Networks are broadly classified into two types: Local
Area Network (LAN) and Wide Area Network (WAN)
• Local Area Network (LAN) as compared to WAN:
• Limited to a small geographic coverage
• Has much higher data transmission rate
• Experiences fewer data transmission errors
• Has lower data communication cost
• Typically owned by a single organization
• Networks that share some of the characteristics of both
LANs and WANs are referred to as Metropolitan Area
Network (MAN)
Ref. Page 342 Data Communications and Computer Networks Slide 22/36

23. Communication Protocols
• Protocol is a set of formal operating rules, procedures,
or conventions that govern a given process
• Communication protocol describes rules that govern
transmission of data over communication networks
• Roles of communication protocol:
Data
Data
Data
Flow
sequencing
routing
formatting
control
•
•
•
•
• Error control
(Continued on next slide)
Ref. Page 343 Data Communications and Computer Networks Slide 23/36

24. Communication Protocols
(Continued from previous slide)
• Precedence and order of transmission
• Connection establishment and termination
• Data security
• Log information.
• Communication protocols are normally split up into a
series of modules logically composed of a succession of
layers.
• Terms protocol suite, protocol family, or protocol stack
are used to refer to the collection of protocols (of all
layers) of a network system
Ref. Page 343 Data Communications and Computer Networks Slide 24/36

25. Network Interface Card (NIC)
• Hardware device that allows a computer to be
connected to a network, both functionally and
physically
• Printed circuit board installed on to one of the
expansion
• Provides a
attached
slots of computer
port on the back to which network cable is
Ref. Page 344 Data Communications and Computer Networks Slide 25/36

26. The OSI Model
The Open System Interconnection (OSI) model is
framework for defining standards for linking
heterogeneous computers in a packet switched
network
Standardized OSI protocol makes it possible for any
two heterogeneous computer systems, located
anywhere in the world, to easily communicate with
each other
•
•
Separate set of protocols is defined for each layer
seven-layer architecture. Each layer has an
independent function
in its
•
Ref. Page 344 Data Communications and Computer Networks Slide 26/36

27. Layers, Interfaces, and Protocols
in the OSI Model
Node 2
Node 1
Application protocol
Presentation protocol
Session protocol
Transport protocol
Network protocol
Data-link protocol
Physical protocol
Network
Ref. Page 346 Data Communications and Computer Networks Slide 27/36
Process B
Layer 7
(application)
Interface
Layer 6
(presentation)
Interface
Layer 5
(session)
Interface
Layer 4
(transport)
Interface
Layer 3
(network)
Interface
Layer 2
(data link)
Interface
Layer 1
(physical)
Process A
Layer 7
(application)
Interface
Layer 6
(presentation)
Interface
Layer 5
(session)
Interface
Layer 4
(transport)
Interface
Layer 3
(network)
Interface
Layer 2
(data link)
Interface
Layer 1
(physical)

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Ref. Page 348 Data Communications and Computer Networks Slide 28/36
Process A
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29. Internetworking
• Interconnecting two or more networks to form a single
network is called internetworking, and the resulting
network is called an internetwork
• Goal of internetworking is to hide details of different
physical networks, so that resulting internetwork
functions as a single coordinated unit
• Tools such as bridges, routers, brouters, and gateways
are used for internetworking
• The Internet is the best example of an internetwork
Ref. Page 348 Data Communications and Computer Networks Slide 29/36

30. Bridges
• Operate at bottom two layers of the OSI model
• Connect networks that use the same communication
protocols
protocols
above data-link layer but may use different
at physical and data-link layers
Ref. Page 349 Data Communications and Computer Networks Slide 30/36

31. Routers
• Operates at network layer of the OSI model
• Used to interconnect those networks that use the same
high-level protocols above network layer
• Smarter than bridges as they not only copy data from
one network segment to another, but also choose the
best route for the data by using routing table
Ref. Page 349 Data Communications and Computer Networks Slide 31/36

32. Gateways
• Operates at the top three layers of the OSI model
(session, presentation and application)
• Used for interconnecting dissimilar networks that use
different communication protocols
• Since gateways interconnect dissimilar networks,
protocol
them
conversion is the major job performed by
Ref. Page 349 Data Communications and Computer Networks Slide 32/36

33. Wireless Computing Systems
• Wireless computing system uses wireless communication
technologies for interconnecting computer systems
• Enhances functionality of computing equipment by freeing
communication from location constraints of wired
computing systems
• Wireless computing systems are of two types:
Fixed wireless systems: Support little or no
mobility of the computing equipment associated with
the wireless network
Mobile wireless systems: Support mobility of the
computing equipment to access resources associated
with the wireless network
•
•
Ref. Page 349 Data Communications and Computer Networks Slide 33/36

34. Wireless Technologies
• 2G and 3G
• Wireless LAN
• WiMAX
• Wireless Local Loop (WLL)
• Radio-router
• Multihop
• Wireless
Wireless Network
Application Protocol (WAP)
Ref. Page 351 Data Communications and Computer Networks Slide 34/36

35. Distributed Computing Systems
Configuration where many independent computer
•
systems are connected, and messages, processing task,
programs, data, and other resources are transmitted
between cooperating computer systems
Such an arrangement enables sharing of many
•
hardware and software resources as well as information
among several users who may be sitting far away from
each other
Ref. Page 352 Data Communications and Computer Networks Slide 35/36

36. Main Advantages of Distributed
Computing Systems
• Inherently distributed applications
• Information sharing among distributed users
• Resource sharing
• Shorter response times and higher throughput
• Higher reliability
• Extensibility and incremental growth
• Better flexibility in meeting users’ needs
Ref. Page 353 Data Communications and Computer Networks Slide 36/36