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�ݺ�ߣ 1M Akram Mujahid
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 .

Title
Computer Communications and
Networks

Text Books
? Data Communications and Networking by Behrouz
A. Forouzan, Fifth Edition
? Data and Computer Communications by William
Stallings, Eighth Edition

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.

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 .

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.

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.

? 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 .

Networks
? A network is a set of devices connected by
communication links .

Networks
Network
Local-Area Network
(LAN)
Metropolitan-Area Network
(MAN)
Wide-Area Network
(WAN)

Local Area Network

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

? 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.

Wide Area Network

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

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.

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.

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.

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.

Unicode
? Unicode uses 16 bits and can represent up to 65536
symbols.
? Unicode also represents symbols belonging to
languages other than English.

ISO
? (International Organization for Standardization ) has
designed a code using a 32-bit pattern.
? This code represents up to 4,294,967,296 symbols.

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

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

Audio
? Audio is representation of sound .Audio is by nature
different from text , numbers , or images. It is
continuous ,not discrete .

Video
? Video can be produced either as a continuous entity
,or it can be a combination of images.

? End of the Lecture

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