cn lecture 1
TRANSCRIPT
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Computer Networks
Lecture 1 By, Ms.Syeda Asima Sarfraz
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Main Topics • Course Aims & Objective
• Study Material
• Introduction to data communications & networks – A communication Model
– Data Communications – Data Representations
– Data Flow
– Computer Networks
– Network Definition
– Distributed Processing
– Network Attributes• Connection Types
• Physical topology
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Course Aims & Objectives • Fundamental Concepts of data communication &
networks
• Understanding of layered architecture (OSI Model)
•
Transmission medias• Encoding & Modulation
• Error detection & flow & error control
• Network devices & LAN technologies
• Switched networks
• IP Addressing & sub netting concepts
• LAN implementation skills
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Study Material • Text Book/s
– Data Communication & Networking
By Behrouz A.Forouzan
– Data & Computer Communications
By William Stallings
• Internet
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Introduction to
Data Communication & Networks • Data
– Refers to information presented in whatever form
is agreed upon by the parties creating and using
data
• Data Communication
– Exchange of data between two devices via some
form of transmission medium such as wire/cable – Communication system is made up of hardware
and software
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Characteristics of
Data Communication System • Effectiveness of data communication depends
upon three fundamental characteristics:
– Delivery
• Must deliver to correct destination
– Accuracy
• Must deliver data accurately
– Timeliness• Must deliver data in timely manner
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Components of
Data Communication System • Data Communication System has five
components – Message
• Data/information to be communicated
– Sender• Device that sends data
– Receiver• Device that receives message
–Medium• Physical path by which message travels
– Protocol• Set of rules that governs data communication
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Data Representation • Data comes in different forms:
– Text• Use Bit pattern
• No. of bits depends upon the no of symbols in language
• Bit pattern is called code• Process of representation is called coding
• ASCII, UNICODE etc.
– Number• Use Bit pattern
• ASCII is not used for numbers
• Directly represented in binary pattern
• Its due to the simplification of mathematical operations
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Data Representation
– Images• Use Bit pattern
• Image is divided into matrix of pixels
• Each pixel is assigned a bit pattern
•
For colored images pixel is decomposed into three primarycolors (RGB)
– Audio• Its continuous not discrete
• Audio is converted into digital signal
– Video• Its continuous
• Converted into digital
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Data Flow • Simplex
– Unidirectional
• Half Duplex
– Each station can send and receive but not the
same time
• Full Duplex
– Both stations can send and receive simultaneously
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Data Flow
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Computer Networks – Network is set of devices connected by
communication link
– Devices are often referred to as Nodes
– Node in a network can be computer, Printer or anyother device capable of sending and receiving
data
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Computer Network • A computer network, often simply referred to as
a network, is a collection of computers
• Devices interconnected by communicationschannels that facilitate communications amongusers
• Allows users to share resources
• Networks may be classified according to a widevariety of characteristics
• A computer network allows sharing of resourcesand information among interconnected devices.
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Distributed Processing • Most networks use distributed processing
• Task is divided among multiple computers
•
Instead of single large machine separatecomputers handle a subset of task
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Distributed Processing
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Network Criteria • Performance
– Can be measured in many ways
– Transit time, response time
– Depends upon number of factors• No of users
• Type of transmission medium
• Capabilities of connected hardware
• Efficiency of software
• Reliability – Measured by frequency of failure
– Time taken to recover from failure
• Security – Protection from unauthorized access
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Computer Network Attributes • Physical structure of network can be seen
through,
– Types of Connection
– Physical Topology
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Type of Connection • There are two possible types of connections:
Point to Point:
• dedicated link between two devices
•
entire link capacity used by two devices
Multipoint
• Also called multi drop
• Connection is one in which more than two specificdevices share single link
• Channel capacity is shared(spatially or temporally)
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Thanks