Communications and Networks Chapter 9 9-1Copyright © 2011 by The McGraw-Hill Companies, Inc. All...

Communications and Networks

Chapter 9

9-1 Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.

• Discuss connectivity, the wireless revolution, and communication systems.

• Describe physical and wireless communications channels.

• Discuss connection devices, and services including dial-up, DSL, cable, satellite/air, and cellular.

• Describe data transmission factors, including bandwidths

and protocols.

Competencies (Page 1 of 2)

9-2 Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.

Competencies (Page 2 of 2)

• Discuss networks and key network terminologies.• Describe different types of networks, including local, home,

wireless, personal, metropolitan, and wide area networks.• Describe network architectures, including topologies, and

strategies.• Describe organization issues related to Internet

technologies and network security.

9-3 Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.

Communications

9-4

The process of sharing data, programs, and information between two or more computers

Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.

Communications Today • Numerous applications depend on communication

systems—E-mail, Instant messaging (IM), Internet telephone, and Electronic commerce

• Connectivity uses computer networks to link people and resources

• Going wireless has been the most dramatic change

9-5 Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.

Communication Systems• Four basic elements

– Sending and receiving devices– Communication channel– Connection devices– Data transmission specifications

9-6 Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.

• Channels carry data from one computer to

another

• Two categories of communication

channels

– Physical connection

– Wireless connection

Communication Channels

9-7 Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.

• Ethernet cable

(Twisted pair cables)

• Coaxial cable

• Fiber-optic cable

Physical Connections

9-8Return

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Wireless Connections

• Radio frequency (RF)

– Wi-Fi (wireless fidelity) 802.11

– Bluetooth

• Microwave

– Line of sight

• Satellite

– GPS

• Infrared

– Short distances

– Line of sight

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Communication Channels Summary

9-10 Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.

• Types of signals

– Analog

– Digital

Connection Device Signals

9-11 Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.

• Types of modems– Telephone– DSL– Cable– Wireless

Connection Devices

9-12

Transfer Speeds

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• Dial-Up services• Leased lines – T1

– T3 and DS3 have higher capacity

• Digital subscriber line (DSL)– Uses existing phone lines

– One type widely used is ADSL • Cable

– Uses existing TV cable – Provides speeds as fast as DSL at a lower cost

• Satellite/air connection services – Seven times faster than dial-up– Slower than DSL & cable modem

• Cellular Services - use 3G cellular network

Connection Services

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Typical User Connection Costs & Speeds

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• Measurement of the capacity of the channel

• Categories – Voice band also known as low bandwidth– Medium band – Broadband– Baseband

Bandwidth

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• Set of communication rules

• Standard for Internet: TCP/IP (Transmission control protocol/Internet protocol)– Identification – Packetization

Protocols

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• A computer network is a communication system

• Connects two or more computers

• Allows information exchange

Networks

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Computer Networks• Node• Client• Server• Directory server

• Host • Switch• Network interface

cards (NIC)• Network operating

system (NOS)• Network administrator

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• Local area networks• Home networks• Wireless LAN• Personal Area networks• Metropolitan area networks• Wide area networks

Network Types

9-19

LAN

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• Arrangement is called topology

• Types of network topology– Legacy

• Star• Bus

– Current• Ring• Tree• Hybrid• Mesh

Network Architecture

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Star Network

• Smaller computers linked to a central unit

• Central unit is called the network switch

• Control is maintained by routing

9-21

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Bus Network • Each device handles its own communication

control• There is no host• Has a common connecting cable called a

backbone or bus• All communications travel along this bus

9-22

Return

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Ring Network

• Each device is connected to two other devices

• No central file server or computer

• Useful in a decentralized environment

9-23

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Tree Network

• Several computers linked to a central node

• Also known as a hierarchical network

• Useful in centralized organizations

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Return

• Combination of different topologies

• Large organizations have a complex of smaller networks– Smaller networks use a

variety of configurations – Connected together they

form a hybrid

Hybrid Network

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Return

• Newest type of topology

• Does not use a specific type of layout

• Requires that each node have more than one connection to other nodes

• Wireless technologies are frequently used

Mesh Network

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Principal Network Configurations

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• Terminal

• Client/Server

• Peer-to-peer

• Distributed

Network Strategies

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Organizational Networks• Intranets

– Private network within an organization– Provides information to

employees

• Extranets– Private network that connects organizations– Used to allow suppliers and others access

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Network Security

• Firewalls– Hardware & software– Protects against external threats

• Intrusion detection systems (NIDS)• Virtual private networks (VPN)

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