This document provides an introduction to data communication. It discusses key topics such as: - Data communication involves the exchange of data between devices via transmission media. - Common transmission modes include simplex, half-duplex, and full-duplex. - Communication channels include narrowband, voice band, and broadband channels. - Computer networks allow simultaneous access to shared data and devices from multiple nodes.

1. Welcome to my Lecture
on
Data Communication
M. Mozammel Hoque Chowdhury
Associate Professor
1

2. Chapter 1
Introduction
1.2

3. 1-1 DATA COMMUNICATION
Data communication is the exchange of data between two
devices via some form of transmission medium such as a wire
cable.
---or--Data Communication is the process of transporting data using
computer devices from one point to another.
Figure 1.1 Five components of data communication
1.3

4. Data Transmission Modes (Ways)
The way of data transfer is called transmission
mode.
● Simplex (Ex. Data transmission from computer to monitor)
● Half Duplex (Ex. Data transmission through Walkie-talkie)
● Full Duplex (Ex. Data transmission through Telephone/cable)
1.4

5. Communication Channel
Communication channel is the link or path between sender and receiver.
Communication Channels are grouped into three basic categories:

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Narrowband
Voice Band
Broadband
Narrowband channels range in speed from 45 to 300 bps (bits per
second). This channel is used mainly for telegraph line and low-speed
terminals.
Voice band channels can transmit data at speeds up to 9600 bps. It is
so called because its major application is for ordinary telephone voice
communication.
Broadband/wideband channels are used when large volumes of data is
to be transmitted at high speed. This system provides data transmission
rate of 1 million bps or more. These channels are used for high
speed computer-to-computer data communication.
1.5

6. Channel Capacity/Bandwidth
Bandwidth defines the volume of signals that can be
transmitted through a communication channel.
So, it defines how much data/information can be transmitted
in one second. It is usually measured in Hertz (Hz) - cycle
per second.
1.6

7. 1-2 COMPUTER NETWORK
► A computer network is a set of computers, printers,
and/or other devices capable of sending and
receiving data connected via communication links.
The computer or other devices are often referred as
nodes.
1.7

8. The Uses of a Computer Network

Simultaneous access to data
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Shared peripheral device
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Data files are shared
Shared files stored on a server
Software can be shared
Printers and faxes are common shares
Reduces the cost per user
Devices can be connected to the network
Print servers control network printing
Personal communication
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Email
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Conferencing
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1.8
Instantaneous communication
Tele conferencing
Videoconferencing
Audio-conferencing
Data-conferencing
Voice over IP
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Phone communication over network wires

9. An overview of Computer Network
1.9

10. Network Types

Local Area Network (LAN)
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Designed in one office or building of up to a few of kilometers.
An organization may have several LANS
Share printers, faxes, computers and servers.
Traditional LANs run at speeds of 10 – 100 Mbps, newer
LANs can operate at higher speeds, up to hundreds of Mbps
Wide Area Networks (WAN)
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1.10
Two or more LANs connected over a large geographic area
Typically use public or leased lines
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Phone lines
 Satellite
The Internet is an example of WAN.

11. Network Types…
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Campus Area Networks (CAN)
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Metropolitan Area Network (MAN)
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1.11
A LAN in one large geographic area
Resources related to the same organization
Each department shares the LAN
Large network that connects different organizations
Shares regional resources
A network provider sells time

12. How Networks Are Structured
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Server based network
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1.12
Node is any network device
Servers control what the node accesses
Users gain access by logging in
Server is the most important computer

13. How Networks Are Structured
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Client/Server network
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Nodes and servers share data roles
Nodes are called clients
Servers are used to control access
Database software
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1.13
Access to data controlled by server
Server is the most important computer

14. How Networks Are Structured
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Peer to peer networks (P2PN)
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1.14
All nodes are equal
Nodes access resources on other nodes
Each node controls its own resources

15. The History about Computer Network
1966 Terms, packets and packet switching, are coined out.
A project was funded to create an experimental network.
1969 The project evolves into Advanced Research Projects
Agency Network (ARPANET).
The first four nodes of ARPANET were:
– BBN (Bolt, Beranek and Newman), a consulting company
– SRI (Stanford Research Institute)
– The Univ. of California
– The Univ. of Utah
1.15

16. 1.16

17. The History about Computer Network…
1971
ARPANET has 15 sites, 23 hosts
1972
FTP is outlined in 1972;
E-mail is created in 1972 by Ray Tomlinson of BBN;
1974
1977
1978
1982
1.17
Telnet protocol is proposed in his year.
Vinton Cerf, propose the Transmission Control Protocol
(TCP) in the paper, “A Protocol for Packet Network
Internetworking”, which introduce the term Internet.
The first wireless gateway is connected to ARPANET,
which transmits packet over radio waves.
Vinton Cerf, launch the plan for Internet Protocol (IP), which
is proposed as a routing function that is separated from
TCP.
TCP and IP are adopted as the main protocol suite for
ARPANET

18. The History about Computer Network…
1983 ARPANET reaches 500 and becomes a truly civilian-based
network, which marks the arrival of Internet
1988 The Internet grows to 60,000 hosts
Europe & North America are linked by fiber-optic cable
Internet Worm, the 1 st internet virus , impacts 10% of the
internet computers
1993 > 2 million hosts, 17 countries in Africa, Asia, …, joined Internet
1999 > 16 million hosts, US law establishes domain names as
property, US Internet backbone reach the speed at 2.5Gbps
2000 IPv6 is used for internet,
The push to implement wireless communication is on.
1.18

19. Network Topologies
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Topology
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1.19
Logical layout of wires and equipment
Several different types

20. Network Topologies
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Bus topology
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Also called linear bus
One wire connects all
nodes
Terminator ends the wires
Advantages
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Disadvantages
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1.20
Easy to setup
Small amount of wire
Slow
Easy to crash

21. Network Topologies
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Star topology
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All nodes connect to a hub
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Advantages
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1.21
Easy to setup
One cable can not crash
network
Disadvantages
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Packets sent to hub
Hub sends packet to
destination
One hub crashing downs
entire network
Uses lots of cable
Most common topology

22. Network Topologies
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Ring topology
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Nodes connected in a circle
Tokens used to transmit data
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Nodes must wait for token to
send
Advantages
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Disadvantages
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1.22
Time to send data is known
No data collisions
Slow
Lots of cable

23. Network Topologies
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Mesh topology
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All computers connected
together
Internet is a mesh network
Advantage
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Disadvantages
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1.23
Data will always be delivered
Lots of cable
Hard to setup

24. Tree Topology
Advantage:
When one hub breaks only
stations connected to the
broken hub will be affected.
1.24

25. Hybrid Topology
1.25

26. Network Hardware
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Network linking devices
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1.26
Connect nodes in the network
Cable runs from node to device
Crossover cable connects two computers

27. Network Hardware
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Hubs
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1.27
Center of a star network
All nodes receive transmitted packets
Slow and insecure

28. Network Hardware
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Switches
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1.28
Replacement for hubs
Only intended node receives transmission
Fast and secure

29. Network Hardware
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Bridge
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Connects two or more LANs together
Packets sent to remote LAN cross
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1.29
Other packets do not cross
Segments the network on MAC addresses

30. Network Hardware
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Router
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1.30
Connects two or more LANs together
Packets sent to remote LAN cross
Network is segmented by IP address
Connect internal networks to the Internet
Need configured before installation

31. Bridge vs. Router
The purpose of both bridge and router is to connect two or
more LANs of the same type.
Bridge forwards data from one network to all other
networks connected to it with desired and no-desired
networks.
On the other hand, router sends data to the desired
machine on the desired network.
So, in case of bridge, network traffic jam occurs, but which
is not applicable for router.
1.31

32. Network Hardware
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Gateway
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1.32
Connects two dissimilar networks
Most gateways contained in other devices

33. Network Interface Cards
1.33

34. Network Protocols
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Language of the network
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1.34
Rules of communication
Error resolution
Defines collision and collision recovery
Size of packet
Naming rules for computers

35. Network Protocols
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TCP/IP
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Transmission Control Protocol/Internet Protocol
Most popular protocol
Machines assigned a name of 4 numbers
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Dynamic Host Configuration Protocol (DHCP)
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1.35
IP address
209.8.166.179 is the White House’s web site
Simplifies assignment of IP addresses
Required for Internet access

36. Why IPv6
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IPv6 is a new version of IP (128 bits)
IPv4 – the current IP is going to run out of address
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To provide more support to new requirements, like
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1.36
Internet growing too fast,
Also have some waste : half of B Class networks have
less 50 hosts.
Better support to real time services, such as video on
demand
Support roaming without change IP
Will be more security

37. Other Network Protocols
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IPX/SPX
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NetBEUI
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1.37
Internet Packet Exchange/Sequenced Packet
Exchange
Older protocol
Associated with Novell Netware
Replaced by TCP/IP
Network BIOS Extended User Interface
Used by Windows to name computers
Transmission details handled by TCP/IP

38. ISO’s OSI Reference Model
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ISO:
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OSI Reference Model:
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1.38
International Standards Organization
A voluntary organization founded in 1946.
Its members are the national standards organizations
like, ANSI(US), BSI (British), IEEE (Institute of
Electrical and Electronics Engineers)
Open System Interconnected Reference Model

39. OSI Reference Model
1.39

40. THE INTERNET
The Internet has revolutionized many aspects of our daily
lives. It has affected the way we do business as well as the
way we spend our leisure time. The Internet is a
communication system that has brought a wealth of
information to our fingertips and organized it for our use.
• Internet is a worldwide system of interconnected computer
networks, which is also called a network of networks
interconnected through regional and national backbone
connections.
1.40

41. Internet related Terms

WWW: The World Wide Web, commonly known as the
Web, is a system of interlinked hypertext documents
accessed via the Internet.
With a web browser (e.g. Internet Explorer, Mozilla
Firefox etc.), one can view web pages that may contain
text, images, videos, and other multimedia and navigate
between them by using hyperlinks.
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1.41
E-mail: Electronic mail, is a method of exchanging
digital messages.
Facebook: Facebook is a social utility that connects
people with friends and others who work, study and live
around them. People use Facebook to keep up with
friends and others.

42. Internet related Terms…
●
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1.42
Intranet : An internal corporate or government
network that uses Internet tools, such as Web
browsers, and Internet protocols.
Extranet: A network that uses the Internet to
link multiple intranets.
DNS (Domain Name System) address
Domain name: nub.edu
Sub-domain: cse.nub.edu

43. Terms
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1.43
WWW
HTTP
ISP
HML
URL
FTP
IRC
DNS
Abbreviation
World Wide Web
Hyper Text Transfer Protocol
Internet Service Provider
Hyper Text Markup Language
Uniform Resource Locator
File Transfer Protocol
Internet Relay Chat
Domain Name System

44. Role of MODEM in Data
Communication MOdulator (who performs Modulation)
MODEM : comes from
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and DEModulator (who performs Demodulation)
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1.44
MODEM performs digital modulation and demodulation.
Modulation – the process of converting digital signals to analog signals
Demodulation – the reverse process of modulation, i.e. converting
analog signals back to digital signals.

45. Why Modulation is Necessary
Modulation is a scheme under which the signal is first modified to
suitable form and mixed with the carrier for transmission.
 To transfer the message signal from one site another site over a long
distance without any interference and loss for that we are using
modulation.
Modulation is important due to following basic reasons :
 Low frequency signals can't be transmitted for long distance. That's why
we are modulating the information signals.
 Need of bandwidth: suppose many people are talking at the same time,
we just cant make out the difference who is talking what, so bandwidth
is provided to each wave and it is done over high frequency to save the
quality of signal.

1.45

46. Why Modulation is Necessary….

Height of antenna: when we want to transmit electrical signal over an
antenna, through free space, it must be converted into electro-magnetic
waves. Only electro-magnetic waves have the property to travel through
space (vacuum) at the speed of light.
For better transmission the height of antenna should be quarter half of
the wavelength of wave to be transmitted. so, frequency is increased
(wavelength decreased) to make it practically possible.
Now suppose we want to transmit, an electric signal having frequency 3
kHz (voice frequency) over an antenna. Then what happens:
It means that we need height of antenna equal to 100 km! This is practically
impossible!
1.46