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INTRODUCTION TO DATA COMMUNICATION
DEFINITION OF DATA COMMUNICATION
“Data Communication is the exchange of Information from one entity to the other using a Transmission Medium ”.
DEFINITION OF DATA COMMUNICATION (Cont’d)
As you can clearly notice, the definition of Data Communication although Simple leaves many questions unanswered:
Exchange?????? Information????? Entities??????? Transmission???? Medium????
We will try to answer all these Questions in this Course
History of Data Communication
Data communications history represents a blend of histories, including:
The history of the telecommunications industry The history of data communications, and The history of the Internet
Telegraph 1837 Samuel Morse
Modern telecommunication industry began in 1837 with the invention of the telegraph by Samuel Morse
This led to building a telecommunications infrastructure of poles and wires as well as to the development of communication hardware and protocols
Telephone 1876 Alexander Graham Bell
Invention of telephone by Alexander Graham Bell in 1876 and the development of wireless communication technology by Guglielmo Marconi in the 1890s set the stage for today’s communication industry
By 1950’s
By 1950s, telephone and telegraph companies had developed a network of communication facilities throughout the industrialized world
1970’S
Although development of databases, languages, operating systems, and hardware was strong from 1950s to 1970s, large-scale data communication systems did not emerge until the 1970s.
This was stimulated by 3 major developments :
Large-scale integration of circuits reduced cost and size of terminals and communication equipment
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New software systems that facilitated the development of data communication networks Competition among providers of transmission facilities reduced the cost of data circuits
TODAY’S EVERGHANGING & BUSY WORLD
o Today’s fast world demands better, secure and most of all FAST ways of communication o Gone are the days when you had to wait a couple of weeks to get a letter from USA o Why wait ONE week when you can get the information you require in just a split of a second, using what we know by the name of “ DATA COMMUNICATION”.
HOW TO ACHIEVE THIS?
o How to achieve this ACCURACY, SECURITY and SPEED for the transfer of this information? o What HARDWARE and the SOFTWARE is needed? o And, what should be the MEANS of sending this info?
ARE SOME OF TOPIC WE WILL BE EXPLORING DURING THE COURSE OF OUR STUDY
DATA COMMUNICATION
o When we communicate , we share information o Information can be LOCAL or REMOTE o Between Individuals LOCAL communication occurs face to face o REMOTE communication occurs over a long distance o When we refer to COMPUTER SYSTEMS, Data is represented in the form of Binary Units (Bits) in the form of Zeros (0’s) and One’s (1’s) o Also the entities can most of the times be considered to be COMPUTERS
Data Communication Definition (Modified)
Therefore, our earlier definition can easily be modified to:
“Data Communication is the exchange of data (in the form of 0’s and 1’s) between two devices (computers) via some form of the transmission medium.”
LOCAL and REMOTE Data Communication
LOCAL
Data communication is considered to be local if the communicating devices are present in the same building or a similarly restricted geographical area
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MESSAGE
Information or Data to be communicated ation of these
Data Communication Messages
Files
Can be text, numbers, video or any combin In short anything that can be represented using binary bits
(meaningful collections of records) Data/information requests (database queries, Web page requests,
nses
etc.) Respo to requests and commands or error messages Status messages (about the network’s functional status) Control messages transmitted between network devices to control
e
network traffic Correspondenc among network users
MESSAGE TYPES
Device that sends the data message ideo camera etc ght not be in the
RECEIVER
Device that receives the message elevision etc n medium may not be in a proper form to be supplied to the receiver and it must be processed
SENDER
SENDER
Can be a Computer , Workstation, V As already discussed, the data from the sender mi appropriate format for the transmission medium and will need to be processed
Can be a computer, workstation, T At times, the data received from the transmissio
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MEDIU
Physical path that a message uses to travel from the Sender to the iver Can be a Copper Cable (Telephone), Coaxial Cable (Cable TV),
see that Data needs to be transferred in the form of
M
Rece
Fiber Optic Cable, LASERS or Radio Waves (Wireless Medium) We will ELECTROMAGNETIC signals and The Transmission Medium should be capable of carrying these EM Signals Transmission Media
Transmission Media
Medium Speed Cost
Tw isted Wire 300bps-10Mbps Low
Microwave 256Kbps-100Mbps Low
Coaxial Cable 56Kbps-200Mbps Low
Fiber Optic Cable 500Kbps-10Gbps High
PROTOCOL
Set of Rules Governing Communication nts an Agreement between communication devices Without Protocol, two devices may be connected but they will not
can only communicate provided they both speak the same language.
A little
Represe
be able to communicate
EXAMPLE : Consider the communication between two individuals. They
more complex Comm. System docsity.com
The data viewed by user m’ will usually be an exact copy of the data sent ‘m’
EXAMPLE-Telephone System
o Input to the Telephone is a message ‘m’ in the form of sound waves o The sound waves are converted by telephone into electric signals of the same frequency o These signals are transmitted w/o any modification over the telephone line o Hence g(t) and s(t) are identical o S(t) will suffer some distortion so that r(t) will not be the same as s(t) o R(t) is converted back to sound waves with no attempt of correction or improvement of signal quality
o Thus m’ is not an exact replica of m
An Actual Digital Data Communication System Key Data
Communication Terminology
Session : communication dialog between network users or applications Different Types of this session for Info Exchange Network : interconnected group of computers and communication devices We will look into it in a little bit Node : a network-attached device Node can be any device in the network
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Summary Data Communication Brief History of Communication Data Communication System Key Data Communication Terminology
Reading Sections Section 1.2, “Data Communications and Networking” 4th Edition by Behrouz A. Forouzan Sections 1.1, 1.2, “Data and Computer Communication” 6th Edition by William Stallings
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