Communications and networks (NHẬP môn điện TOÁN SLIDE)

• Computer communications is the process of sharing data, programs, and information between two or more computers • Numerous applications depend on communication systems, including –

Chapter 9 Communications and

Networks

Chapter 9 Communications and

Networks

• We live in a truly connected society

• Increased connectivity potentially

means increased productivity,

especially in business

• You will learn more about the

concept of connectivity and

the impact of the wireless

revolution in this chapter.

• Computer communications is the process

of sharing data, programs, and

information between two or more

computers

• Numerous applications depend on

communication systems, including

– E-mail– Instant messaging– Internet telephone– Electronic commerce– Global positioning systems (GPS)

• Connectivity uses computer networks

to link people and resources

• The Wireless Revolution

– Single most dramatic change in

connectivity and communications has been widespread use of mobile telephones with wireless Internet connectivity

• Four basic elements

– Sending and receiving devices– Communication channel

– Connection devices– Data transmission specifications

• Communication channels carry the

data from one computer to another

• Two categories of communication

channels

– Physical connection – Wireless connection

• Typical user connection costs,

bandwidth speeds, and comparable

time required to download an image

in the USA

Connection Costs and Speeds

• Measurement of the width or capacity

of the communication channel

• Categories

– Voice band (or low bandwidth)– Medium band

– Broadband– Baseband

• Communication rules for exchanging

data between computers

• Internet standard: TCP/IP

• A computer network is a communication

system that connects two or more

computers

• Allows exchange of information and

resources

• Arrangement is called topology

• Types of network topology

• Each device is connected to a

common cable, called a bus or

• No central file server or computer

• Useful in a decentralized environment

Return

• Most widely used network topology

for both homes and large businesses

• Each device connects directly to a

central network switch

Return

• Each device is connected to a central

node, either directly or through

subordinate nodes

• Also known as a hierarchical network

Return

• Combination of different topologies

• Large organizations have a complex

network of smaller networks

– These smaller networks use a

variety of configurations

– When connected together, they

form a hybrid

Return

• Does not use a specific physical

layout, but requires that each node

have more than one connection to

other nodes

• Wireless technologies are frequently

used

– Private network within an organization

– Works like the Internet, where employees

use browsers to access Web sites and Web pages

• Extranets

– Private network that connects organizations

– Works like the Internet, but provides

suppliers and other trusted partners with limited access to the organization’s

networks

connection between your computer and the organization

Chapter 9 Communications and

Networks

Communications and

Networks

STUDY p274 – 279