Extended Learning Module ENetwork Basics

Copyright © 2010 by the McGraw-Hill Companies, Inc. All rights reserved.McGraw-Hill/Irwin

STUDENT LEARNING OUTCOMES1. Identify and describe the four basic concepts

on which networks are built and describe what is needed to set up a small peer-to-peer network at home.

2. Describe the components used to build large business networks and define and compare local area networks (LANs), wide area networks (WANs), and metropolitan area networks (MANs).

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STUDENT LEARNING OUTCOMES3. Compare and contrast the various Internet

connection possibilities.

4. Compare and contrast the types of communications media.

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STUDENT LEARNING OUTCOMES5. State the four principles of computer security

and describe how different network security devices reflect those principles.

6. Describe client/server business networks from a business and physical point of view.

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INTRODUCTION

Computer network – two or more computers connected so that they can communicate with each other and share information, software, peripheral devices, and/or processing power

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INTRODUCTION

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Basic Principles of Networks

Four main principles

1. Each computer must have a network interface to provide a doorway for information

2. The network usually has at least one connecting device

3. The network must have communications media to transport information

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Basic Principles of Networks

4. Each computer must have software to move information in and out of the computer

These four principles apply to all networks, large and small

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HOME NETWORKS

A typical home network setup has1. An Ethernet network card in each computer or a

wireless card in each laptop

2. Network cables to transmit signals, or no cables for wireless

3. A DSL or cable modem connection and a broadband/home router

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Network Cards

Network interface card (NIC) – an expansion card or PC card that connects your computer to a network Ethernet card – the most common type of

network interface card Built into the motherboards of many new

computers – looks like a telephone jack, but wider

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Wired Transmission Media

Cat 5 (Category 5) cable – better-constructed version of phone twisted-pair cable

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Wireless Transmission Media

Wireless Access Point (WAP) – device that allows a computer to use radio waves to access a network

Connects to hub or switch with a cable like a wired computer

May be built into broadband router and not require separate cabling

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Home Internet Service

Broadband router or home router – a device to connect computers together to share DSL or cable Internet service in a home or small office One port to plug into DSL or cable connection to

connect to the Internet Usually several ports to build a network for home

computers or printers and share Internet connection

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Network Software

Makes each computer's hardware work Can use Windows Turn on filesharing to make files available to

other computers on the network

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NETWORK COMPONENTS

Hub – a device that connects computers into a network and repeats all transmissions to every connected computer Only one computer can transmit at a time All computers see every message Can have collisions when two computers try to

transmit at the same time

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NETWORK COMPONENTS

Switch – a device that connects computers and repeats transmissions only to intended recipient Multiple conversations can occur simultaneously

between different sets of computers Only recipient computer sees each message Computers can still broadcast messages to all

other computers on the network

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NETWORK COMPONENTS

Router – a device that connects subnetworks (subnets) of a larger network Can connect different buildings at same or

different locations Passes transmissions from one network to another May pass through multiple routers on the way

from source to destination

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NETWORK COMPONENTS

More on routers Home/broadband routers often have built-in

switches or hubs Corporate routers generally require separate

switches or hubs Routers must be configured with information about

the networks they connect

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NETWORKS BY DISTANCE

Large networks can be classified by the proximity of the area(s) they serve: Local Area Network (LAN) – network that serves

a building or buildings in a contiguous area

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NETWORKS BY DISTANCE

More networks by distance Wide Area Network (WAN) – a set of connected

networks serving areas not immediately contiguous

Metropolitan Area Network (MAN) – a set of connected networks within the same city or metropolitan area but not in immediate proximity to each other

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THE INTERNET

A vast network of computers that connects people all over the world

Computers pass messages through routers to their ultimate destinations

Each router determines whether it has a direct path to the recipient or whether to send the message on to another router

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Bandwidth

The amount of information that can be transferred in a given amount of time

Usually expressed as bits per second (bps) Higher bandwidths expressed as

kilobits per second (Kbps) – thousands of bits per second

megabits per second (Mbps) – millions of bits per second

gigabits per second (Gbps) – billions of bits per second

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Internet Connection Types

Phone line and dialup modem Phone line and DSL modem Cable TV line and cable modem Satellite modem Dedicated high-speed business lines

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Broadband Internet Connection

Broadband – high-capacity telecommunications line capable of providing high-speed Internet service

All Internet access methods on the previous slide are broadband except the dialup modem

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Dialup Connection

Modem – connects a computer to a phone line to access another computer or network

Modulates outgoing signal from digital to analog form Demodulates incoming signal from analog to digital

form

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Digital Subscriber Line (DSL)

Digital Subscriber Line (DSL) – high-speed Internet connection using phone lines, which allows you to use your phone for voice communications at the same time

Runs at a higher frequency than voice conversations, so not supported on some older phone lines

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Cable Modem

Cable modem – uses your TV cable to deliver an Internet connection

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Satellite Modem

Satellite modem – delivers Internet access from satellite dish

Satellite TV and modem may share same dish or may be separate

Connects to computer or broadband router like cable modem

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T1 and DS3 Business Lines

T1 and DS3 developed by phone companies to carry many long-distance voice conversations

T1 runs up to about 1.5 Mbps DS3 runs up to about 45 Mbps Can carry both voice and network over the

same lines

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Frame Relay and ATM Business Services

Frame Relay and ATM are used to connect many branch offices to the main office

Use virtual circuits to simulate having a line from every office to every other office

Virtual CircuitsVirtual CircuitsMod E-30

Comparison of Connection Types

Telephone modem + Inexpensive and available anywhere there's a

phone line - Slow, and ties up the line for voice calls too

DSL + Higher-speed connection, doesn't tie up the

phone line for voice calls, and can be left on all the time

- Not available in all areas or on all lines

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Comparison of Connection Types

Cable modem + Higher-speed connection, doesn't use the phone

line at all, and always-on - Connection shared with the neighborhood, so

speed may vary

Satellite modem + Available in remote locations where DSL and

cable aren't - High cost

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Comparison of Connection Types

T1 and DS3 + High-speed to very-high-speed connections, can

transmit both voice and data - High cost that may be mileage-dependent

Frame relay and ATM + Use virtual circuits to simulate more inter-office

connections than are physically present - High cost normally affordable only by mid- to

large-scale enterprises

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Voice Over IP

Voice over IP – allows you to send voice communications over the Internet and avoid long-distance toll charges

No long-distance calling cost

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NETWORK COMMUNICATIONS MEDIA Communications media – the paths in a

network over which information travels Wired communications media – transmit

information over a closed, connected path Wireless communications media – transmit

information through the air

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Wired Communications Media

Twisted-pair cable – a bundle of copper wires for transmitting voice or data

Cat 5 and Cat 5e are common for modern networks Coaxial cable (coax) – one central wire

surrounded by insulation, a metallic shield, and a covering of insulation

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Wired Communications Media

Optical fiber – uses a very thin glass or plastic fiber through which pulses of light travel

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Wireless Communications Media

Infrared – uses red light to send and receive information

Bluetooth – a standard for transmitting information in the form of short-range radio waves over distances of up to 30 feet and is used for purposes such as wirelessly connecting a cell phone or PDA to a computer

Microwave – a type of radio transmission Repeater – receives a radio signal, strengthens it,

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Wireless Communications Media

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Wireless Communications Media

Communications Satellite – microwave repeater in space

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NETWORK SECURITY

The four principles of network security are:1. Confidentiality

2. Authenticity

3. Integrity

4. Availability

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NETWORK SECURITY

Confidentiality – information can be obtained only by those authorized to access it Bank statements, credit reports, employee

evaluations Threatened by capture of network transmissions

and easily-guessed passwords

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NETWORK SECURITY

Authenticity – information really comes from the source it claims to come from Military orders, medical diagnoses, stockbroker

directions Threatened by fraudulent e-mails and misspellings

of popular Web site names

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NETWORK SECURITY

Integrity – information has not been altered Bank balance, corporate Web site, prescriptions,

credit card charges Threatened by forged network transmissions and

faulty server software

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NETWORK SECURITY

Availability – a service or resource is available when it's supposed to be Mail-order Web site, corporate e-mail server Threatened by network failures, faulty server

software, and high volumes of malicious network traffic

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Firewalls & Intrusion Detection Systems Firewall – protects a computer from intruders Intrusion detection system (IDS) – watches

for and reports intrusion attempts Intrusion prevention system (IPS) – type of

IDS that also takes action against intrusion attempts

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Encryption

Encryption – scrambles data so you can't read it without having the decryption key

Virtual Private Network (VPN) – encrypts all network transmissions between two endpoints to protect confidentiality and integrity of data

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Firewalls & Intrusion Detection Systems

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Malware

Malware – software designed to harm your computer or security

1. Virus – software written with malicious intent to cause annoyance or damage

2. Worm – spreads itself from computer to computer via e-mail and other network traffic

3. Spyware – collects information about you and reports it to someone else without your permission

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CLIENT/SERVER SOFTWARE MODEL Client/server network – a network in which

one or more computers are servers and provide services to the other computers, called clients

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Client/Server: A Business View

Client/server networks differ according to1. Where the processing for the presentation of

information occurs

2. Where the processing of logic or business rules occurs

3. Where the data management component (DBMS) and information (database) are located

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Client/Server: Model 5

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Five Models of Client/Server

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Five Models of Client/Server

1. Distributed Presentation The server handles almost all functions, including

a major portion of the presentation

2. Remote Presentation The client handles all presentation functions

3. Distributed Logic The server handles all data management, the

client handles all presentation formatting, and the logic processing is shared

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Five Models of Client/Server

4. Remote Data Management The server handles data management only, and

the client processes business rules and formats the presentation of results

5. Distributed Data Management The client handles all presentation formatting and

business rule processing, and both the server and client share data management duties

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