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Text Book

1. “Computer Networks & Internets” by Douglas E Comer.

2. “Data and Computer Communication” by William Stalling,

5th or above edition.

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Marks distribution

Topic no

1,2,3 First Mid 20

Second Mid 20 4,5,6

Selected topics Seminar 10

Quizzes/assignment 10 Based on taught topics

Final Exam 40 all topics

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; Studying networks because

The world is interconnected

Applications now operate in a distributed environment

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Topics of this subject

Network definition and basic Terminology

Network Data Transmission Modes & data

Transmission Mediums

Network Topologies and technologies

Network Devices

Switching Techniques.

Architecture (OSI & TCP/IP reference Model )

Client Server Architecture.

Internet & Its Related Terminology (IP Addressing). 5

Networks

A network is a set of devices at least two (often referred to as

nodes-hosts-Enduser) connected by communication links. A

node can be a computer, printer, or any other device capable of

sending and/or receiving data generated by other nodes on the

network.

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Importance of Networks

Software and file sharing

Hardware sharing

Modern Technologies (IP Telephony, Video Conferencing)

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Depending on one’s perspective, we can classify networks in

different ways;

• Based on transmission media: Wired (UTP, coaxial cables,

fiber-optic cables) and Wireless

• Based on network size: LAN and WAN (and MAN)

• Based on management method: Peer-to-peer and

Client/Server

• Based on topology (connectivity): Bus, Star, Ring …

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Performance Reliability Security

Network Criteria

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Performance

Depends on a number of factors.

number of users

type of transmission medium(data rate)

hardware

software : error-free delivery

Evaluated by two networking metrics:

Throughput and Delay.

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Reliability

Frequency of failure

Recovery time of a network after a failure

Catastrophe

Networks must be protected from catastrophic

events such as fire, earthquake, or theft.

Security

Protecting data from Unauthorized access

Protecting data from Viruses and Worms 11

Data Communications

The term telecommunication means communication at a

distance. The word data refers to information presented in

whatever form is agreed upon by the parties creating and

using the data. Data communications are the exchange of

data between two devices via some form of transmission

medium such as a wire cable.

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The effectiveness of a data communication system

depends on three fundamental characteristics

Delivery

must deliver data to the correct destination (the

intended device or user)

Accuracy

must deliver data accurately

Timeliness

must deliver data in a timely manner

Jitter

Refers to the variation in the packet arrival time. 13

Data communication system components

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Five components of data communication

Message

is the information(data) to be communicated.

(text, numbers, pictures, sound, video or any combination

of these). A group of bits are used to represent a

character/number/special symbol/Control Characters

Sender

is the device that sends the data message.

(computer, workstation, telephone handset, video camera)

Receiver

is the device that receives the message.

(computer, workstation, telephone handset, video camera)

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Medium

is the physically path by which a message travels from

sender to receiver. (twisted pair wire, coaxial cable,

fiber- optic cable, laser , or radio waves(terrestrial or

satellite microwave)

Protocol

is a set of rules that govern data communication. It

represents an agreement between the communicating

devices. Without a protocol, two devices may be

connected but not communicating

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Direction of Data Flow

is used to define the direction of signal flow between two link

devices

Simplex

Half-Duplex

Full-Duplex

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Simplex

Half Duplex

Full Duplex

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Simplex

In simplex mode, the communication is unidirectional, as

on a one-way street. Only one of the two devices on a link

can transmit; the other can only receive.

Keyboards and traditional monitors are examples of

simplex devices. The keyboard can only introduce input;

the monitor can only accept output.

The simplex mode can use the entire capacity of the

channel to send data in one direction.

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Half-Duplex

In half-duplex mode, each station can both transmit and

receive, but not at the same time. When one device is

sending, the other can only receive, and vice versa.

The half-duplex mode is like a one-lane road with traffic

allowed in both directions. When cars are traveling in one

direction, cars going the other way must wait.

In a half-duplex transmission, the entire capacity of a

channel is taken over by whichever of the two devices is

transmitting at the time.

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Full Duplex

In full-duplex mode, both stations can transmit and

receive simultaneously.

The full-duplex mode is like a two way street with

traffic flowing in both directions at the same time.

One common example of full-duplex communication is

the telephone network. When two people are

communicating by a telephone line, both can talk and

listen at the same time.

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