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Learning Objectives
• Introduction of the course.
• Course outline overview.
• To understand the Communication Model ,
• To understand basic terms and definitions in data
communications,
• Overview of computer networks .
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Title
Computer Communications and
Networks
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Text Books
• Data Communications and Networking by Behrouz
A. Forouzan, Fifth Edition
• Data and Computer Communications by William
Stallings, Eighth Edition
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Reference Books
• Data Communications and Computer Networks by
Curt M. White, Course Technology.
• Computer Networks by Andrew S. Tanenbaum.
• Computer Networks and Internets by Douglas
Comer.
• Data Communications by Fred Halsall, Computer
Networks, and Open Systems, Addison-Wesley.
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Course Overview
• Through this course, you will attain a understanding
of data communications , including:
• Terminology
• Digital and analog data signals
• Transmission media
• Flow Control and Error Control
• Circuit Switching and Packet Switching
• Protocols .
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Data Communication
• Data communication is exchange of data between
two devices via some form of transmission medium
such as a wire cable according to a protocol.
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Data Communication System
• The combination of hardware (physical equipment )and
software (programs ) to exchange data is called data
communication system. The effectiveness of a data
communication system depends on three fundamental
characteristics:
• Delivery :The system must deliver data to the correct
destination.
• Accuracy :The system must deliver data accurately.
• Timeliness :The system must deliver data in a timely
manner.
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Data Communication System
• A data communication system has five components.
• Message :The message is the information (data) to
be communicated.
• Sender : Sender is the device that sends the data
message.
• Receiver : The receiver is the device that receives
the message.
• Medium : The transmission medium is the physical
path by which a message travels from sender to
receiver.
• Protocol :A protocol is the set of rules that governs
data communication .
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Local Area Network
• A LAN (Local Area Network) is a group of computers
and network devices connected together, usually
within the same building
• Smaller scope - Building or small campus
• Usually owned by same organization as attached
devices
• Data rates are much higher with low error rates.
• LANs are designed to share resources between
personal computers or work stations.
• LANs are distinguished by their
• Size, Transmission Media, Topology
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Metropolitan-Area Network
• MAN consists of a medium size geographical area.
• The scope of the MAN is always a city ,town or any
two or three near by cities.
• Common example is Cable TV Network.
• A company can use a MAN to connect to all of its
offices throughout a city.
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Wide Area Network
• Large geographical area
• Usually not owned by private organizations
• WANs connect two or more individual networks using
• Transmission lines
• Switching elements / nodes
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WANs vs. LANs
• Wide Scope
• Low data rates
• Usually use Public
Resources
• Commonly
implemented using
circuit switching, packet
switching etc.
• Limited Scope
• High data rates
• Usually under
Private Ownership
• Common
technologies include
Bus, star, Ring,
mesh etc.
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Data Representation
• To day Data comes in different forms such as text
,numbers ,images ,audio and video.
• Text : In data communication text is represented as a
bit pattern (A sequence of bits )
• Different sets of bit pattern have been designed to
represent text symbols. Each set is called a code.
Process of representing symbols is called coding.
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ASCII
• ASCII
• (American Standard Code for Information
Interchange) developed a code that uses 7 bits for
each symbol. this means 128(27) different symbols
can be defined by this code.
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Extended ASCII
• Extended ASCII: To make the size of each pattern
1 byte(8 bits) the ASCII
• bit patterns are augmented with an extra 0 at the
left. Now each patterns is exactly 1 byte of memory.
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Unicode
• Unicode uses 16 bits and can represent up to 65536
symbols.
• Unicode also represents symbols belonging to
languages other than English.
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ISO
• (International Organization for Standardization ) has
designed a code using a 32-bit pattern.
• This code represents up to 4,294,967,296 symbols.
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Numbers
• Numbers are also represented by using bit patterns
.however a code such as ASCII is not used to
represent numbers, the number is directly converted
to binary numbers
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Images
• Images are also represented by bit patterns .an
image is divided into a matrix of pixels (picture
element) where each pixel is a small dot .The size of
pixel depends on what is called resolution. After an
image is divided into pixels each pixel is divided into
bit patterns
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Audio
• Audio is representation of sound .Audio is by nature
different from text , numbers , or images. It is
continuous ,not discrete .
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Video
• Video can be produced either as a continuous entity
,or it can be a combination of images.
