ITC 6 MBA-I Evening

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6

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•

Computers use digital signals--0s and 1s, off and on.

•

All the data that a computer processes is a series of 0s

and 1s.

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Digital Age

•

_Analog

•

But most phenomena in life are analog.

•

Analog signals use wave variations.

•

Sound, light, and temperature are analog forms.

•

Traditional TV and radio use analog signals.

•

Humans’ vision operates in analog mode.

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modems are needed to convert analog data into digital

data that computers can use.



_{Modem is short for modulate/demodulate. Modems}

modulate (convert) a computer’s digital data to analog

data, transmit it, then demodulate (reconvert) it back to

digital data for the receiving computer.



_{Modems can convert data by modulating either a}

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Digital Age



_{Converting Reality to Digital Form--Sampling}



Tape recorders, voices, and musical instruments are

analog; CDs are digital



To burn a CD, the digital recording equipment must

convert from analog to digital

 _{The analog-to-digital converter}_samples_{the sound and}

converts the height of the wave to a number

 Samples of the sound wave are taken at regular intervals –

about 44,100 times each second

 _{Because the digital samples are played back faster than our}

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 Movies show still pictures (frames)

 _{But they show them so fast that our eyes can’t react in time}

 So to us the series of still pictures look like continuous

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6.2 Networks



_{What’s a Network?}



A system of interconnected computers, telephones, and/

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 Share peripheral devices, such as printers, scanners, disk

drives

 _{Share programs and data}

 Better communications, including email

 _{Security of information, because of improved backup}

systems

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6.2 Networks

Category Description

WAN – Wide Area Network Covers a wide geographic area, such as a

country or the world; largest WAN is the internet MAN – Metropolitan Area Network Covers a city or a suburb

LAN – Local Area Network Connects computers and devices in a limited geographic area such as an office, a building, or a group of nearby buildings

HAN – Home Area Network Uses wired, cable, or wireless connections to link a household’s digital devices

PAN – Personal Area Network Uses short-range wireless technology to connect an individual’s personal electronics, such as cellphone, PDA, MP3 player, notebook PC, and printer

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Structures



1. Client/Server

 Consists of clients, which are computers that request data,

and servers, which are computers that supply data

 _{File servers act like a network-based shared disk drive}

 Database servers store data but don’t store programs  _{Print servers connect one or more printers and schedule}

and control print jobs

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6.2 Networks



_{How Networks Are Structured: Two Principal}

Structures (

continued

)



2. Peer-to-Peer (P2P)

 All computers on the network are “equal” and communicate

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6.2 Networks



_{Intranets, Extranets, & VPNs}



Intranets—use infrastructure and standards of the

internet and the web, but for an organization’s internal

use only



Extranets—similar to intranets but allows use by selected

outside entities, such as suppliers



VPNs—virtual private networks: use a public network

(usually the internet) plus intranets and extranets to

connect an organization’s various sites) but on a private

basis, via encryption and authentication; regular internet

users do not have access to the VPN’s data and

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

Wired/Wireless Connections

 _{wired = twisted-pair, coaxial cable, fiber-optic cable}

 wireless = infrared, microwave, Wi-Fi, satellite



Hosts and Nodes: Client/server network has a host

computer, which controls the network; a node is any

device attached to the network.



Packets– fixed-length blocks of data for transmission;

reassembled after transmission; a packet is also called a

datagram, a segment, a block, a cell, or a frame,

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6.2 Networks



_{Network Components (}

_continued

₎



Network Linking Devices

 _{Protocol—set of conventions, or rules, governing the exchange of}

data between hardware and/or software components in the network; built into the hardware or software you are using

 _{Hub—Common connection point for devices on a network; has}

multiple ports and can send to all connected devices

 Switch—Device that connects computers to a network; sends only

to intended recipients

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

Network Linking Devices(

continued

)

 _{Router—Special computer that directs messages among several}

networks

 Backbone—The main internet highway that connects all networks

in an organization; includes gateways, routers, etc.

 _{NIC—Network interface card; inserted in a slot on the}

motherboard, enables computer to operate as part of a network

 NOS—network operating system; the system software that

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6.2 Networks

 _Topologies

 _{Ring – all nodes are}

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

Star – all nodes are

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6.2 Networks



_{Packet Collision Schemes (Protocols)}



Collisions happen when two data packets are going

opposite directions on shared media



Ethernet – deals with LAN collisions

 All devices send data at once  _{Collisions happen regularly}

 Data is resent until it arrives



Token ring – avoids LAN collisions

 _{Devices take turns sending data}

 Token is sent around the ring

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communications path



Twisted-Pair Wire

 2 strands of insulated copper wire twisted around each

other

 Twisting reduces interference (crosstalk) from electrical

signals

 Data rates are 1 – 128 Megabits per second



Coaxial Cable

 Insulated copper wire wrapped in a metal shield and then in

an external plastic cover

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Media



_{Communications media (}

_continued

₎



Fiber-optic cable

 _{Dozens or hundreds of thin strands of glass or plastic that}

transmit pulses of light, not electricity

 Can transmit up to 2 gigabits per second

 _{Have lower error rate than twisted-pair or coax}

 More expensive than twisted-pair or coax

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Ethernet

 Pull Cat5 cables through the house

 Connect to PC’s Ethernet network interface card (NIC)  For several PCs, get a hub or switch to connect them all  10 or 100 megabits per second

 HomePNA

 Uses existing telephone wiring and jacks  _{Requires HomePNA NIC in your PC}

 Speeds of about 320 megabits per second

 Homeplug

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Communications Media



_{Electromagnetic spectrum of radiation is the basis of all}

telecommunications signals, wired and wireless



Radio-frequency (RF) spectrum is the part of the

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transmission medium can carry in a given period of time



Analog bandwidth is expressed in hertz, digital bandwidth

usually in bits per second (bps)



Narrowband (Voiceband): used for regular telephone

communications

 Transmission rate 1.5 megabits per second or less



Broadband: For high-speed data and high-quality audio

and video

 Transmission rate 1.5 megabits per second to 1 gigabit per

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Communications Media



_{TC/IP (Ch. 2) is the protocol for getting wired devices}

connected to the internet



_{WAP (wireless application protocol) gets wireless}

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

Infrared Transmission

 Sends signals using infrared light

 Frequencies are too low to see (1-16 Mbits per second)



Broadcast Radio

 AM/FM, CB, ham, cellphones, police radio

 Sends data over long distances using a transmitter and a

receiver (up to 2 Mbits per second)



Cellular Radio

 Form of broadcast radio

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Communications Media



_{Five Types of Wireless Communications Media}

(

continued

)



Microwave Radio

 Superhigh-frequency radio waves (2.4 gigahertz or higher)  Requires line-of-sight transmitters and receivers

 More than ½ of today’s telephones systems use microwave



_{Communications Satellites}

 Microwave relay stations in orbit around the earth  _{Basis for Global Positioning Systems (GPS)}

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 Can be placed at different heights: GEO, MEO, LEO  _{GEO – geostationary earth orbit}

 22,300 miles above earth; travel at the same speed as the

earth and so appear to us to be stationary

 _{Always above equator}

 _{Transmission delay can make conversations difficult}

 MEO – medium-earth orbit

 _{5,000 – 10,000 miles up}

 _{LEO – low-earth orbit}

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Communications Media



_{Long-Distance Wireless: One-Way Communication}



GPS (Global Positioning System)

 _{24 to 32 MEO satellites continuously transmitting timed}

radio signals

 Each satellite circles earth twice each day at 11,000 miles

up

 GPS receivers pick up transmissions from up to 4 satellites

and pinpoint the receiver’s location

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 _{One-way Pagers}

 _{One-way pagers are radio receivers that receive data sent from a}

special radio transmitter

 Radio transmitter sends out signals over the special frequency  _{Pagers are tuned to that frequency}

 _{When a particular pager hears its own code, it receives and}

displays the message

Question: Why do airplane rules require you to turn off pagers and cellphones during flight?

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Communications Media



_{Long-Distance Wireless: Two-Way Communications}



1G: First-Generation Cellular Service

 _{Analog cellphones}

 Designed for voice communication using a system of

hexagonal ground-area cells around transmitter-receiver cell towers

 Good for voice – less effective for data because of handing

off



2G: Second-Generation Cellular Service

 Uses digital signals

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(

continued)



3G: Third-Generation Cellular Service

 3G cellphones are more like PDAs  Broadband technology

 Carries data at high speeds

 _{High speed data: 144 kilobits per second up to 2.4 megabits}

per second

 Accepts e-mail with attachments

 _{Displays color video and still pictures}

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Communications Media



_{Long-Distance Wireless: Two-Way Communications}

(

continued)



4G: Fourth-Generation Cellular Service

 A nationwide 4G network in development

 Uses the WiMax (Worldwide Interoperability for Microwave

Access) standard

 May provide broadband to rural areas

 _{First 4G phone, the EVO, released in March 2010}

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

Local Area Networks

 _{Range 100 – 228 feet}

 Include Wi-Fi (802.11) type networks

 _{Wi-Fi n is the latest and fastest Wi-Fi technology}



Personal Area Networks

 Range 30 – 32 feet

 _{Use Bluetooth, ultra wideband, and wireless USB}



Home Automation networks

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Communications Media



_{Short-Range Wireless: Two-Way Communications}

(

continued

)



Wi-Fi b, a, g, and n networks

 Named for variations on the IEEE 802.11 standard

(802.11b, 802.11a, 802.11a)

 _{Data ranges: 11 megabits per second up to 126 feet}

indoors (Wi-Fi b) to 54 megabits per second up to 120 feet (Wi-Fi a and g)

 Wi-Fi n with MIMO extends range of Wi-Fi using multiple

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(

continued

)



Wi-Fi Security

 A person with a $50 antenna can eavesdrop on

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Communications Media



_{Short-Range Wireless: Two-Way Communications}

(

continued

)



Personal Area Wireless

 Bluetooth

 Short-range wireless standard to link cellphones, PDAs,

computers, and peripherals at distances usually up to 30 ft

 _{Transmits up to 3 megabits per second}

 When Bluetooth devices come into range of each other, they

(45)

(

continued

)



Personal Area Wireless (

continued)

 Ultra Wideband (UWB)

 _{Developed for military radar systems}

 _{Operates in 480 megabits per second, range up to 30 ft}

 Uses a low power source to send out millions of bursts of radio

waves each second  Wireless USB

 _{USB is the most used interface on PCs}

 _{Range of 32 ft and maximum data rate of 480 megabits per}

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Communications Media



_{Short-Range Wireless: Two-Way Communications}

(

continued

)

 Short-Range Wireless for Home

 _Insteon

 _{Combines electronic power line and wireless technology}  _{Can send data at 13.1 kilobits per second with 150 ft range}  _ZigBee

 Entirely wireless sensor technology

 Can send data at 128 kilobits per second with 250 ft range  Z-Wave

 _{Entirely wireless power-efficient technology}

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among universities and scientists. They trusted each

other. No security was built into the internet.



_{Problem: The internet is open-access and is used by}

criminals who take advantage of the lack of built-in

safeguards.



_{Problem: Most people connect to the internet and use}

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& Safeguards



_Cyberthreats



Denial of Service Attacks

 _{Consist of making repeated requests of a computer or}

network device, thereby overloading it and denying access to legitimate users

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

Worms (Malware)

 _{A program that copies itself repeatedly into a computer’s}

memory or disk drive

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& Safeguards



_{Cyberthreats (}

_continued

₎



Viruses (Malware)

 _{Deviant program that hides on a disk, in an e-mail, or in a}

web link that causes unexpected effects such as destroying or corrupting data

 Viruses are released at the rate of about one per day

 To see what the latest ones are, go to

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

Trojan Horses (Malware)

 _{Programs that pretend to be a useful program such as a}

free game or a screensaver but that carry viruses or

malicious instructions that damage your computer or install a backdoor or spyware

 Backdoors and spyware allow others to access your

(52)

& Safeguards



_{Cyberthreats (}

_continued

₎



How they spread

 _{Via e-mail attachments}

 By infected disks

 _{By clicking on infiltrated websites}

 By downloading infected files from websites

 Through infiltrated Wi-Fi hotspots

 From one infected PC on a LAN to another



What can you do about it?

 _{Install antivirus software and subscribe to the}

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

Cellphone Malware

 _{Spread via internet downloads, MMS attachments, and}

Bluetooth transfers

 Usually show up disguised as applications such as games,

security patches, add-on functionalities, erotica, and free programs

 Protect your phone:

 _{Turn off Bluetooth discoverable mode}

 Check security updates to learn about filenames to

(54)

& Safeguards



_{Cyber Villains}



Hackers are either

 _{Computer enthusiasts, people who enjoy learning about}

programming and computers

 People who gain unauthorized access to computers or

networks, often for fun or just to see if they can

 Two types:

 Thrill-seeker hackers: do it for the challenge

 _{White-hat hackers: do it to expose security flaws that can be}

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

Crackers

 _{Malicious hackers who break into computers for malicious}

purposes

 Script kiddies are technically unsophisticated teenagers who

use downloadable software for perform break-ins

 _{Hacktivists are hacker activists who break into systems for a}

political purpose

 Black-hat hackers are those who break into computers to steal

or destroy information or to use it for illegal profit

 _{Cyberterrorists attack computer systems so as to bring physical}

(56)

& Safeguards



_{Online Safety}



Use antivirus software, and keep it current



Install a firewall to monitor network traffic and filter out

undesirable types of traffic and undesirable sites



Don’t use the same password for multiple sites



Don’t give out any password information



Use robust passwords:

 _{Minimum 8 characters with letters, numbers, characters}

(57)



Install antispyware software



Encrypt financial and personal records so only you can

read them



Back up your data, so if your PC is attacked and must be

reformatted, you can restore your data



Never download from a website you don’t trust

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& Safeguards



_{Online Safety (}

_continued

₎



Biometrics: science of measuring individual body

characteristics

 Used in security devices

 _{Examples; hands, fingerprints, iris recognition, face}

recognition, voice recognition

(59)



Encryption

 _{Process of altering readable data into unreadable form to}

prevent unauthorized access

 Uses powerful mathematical ciphers to create coded

messages that are difficult to break

 Unencrypted messages are known as plain text  _{Encrypted text is known as cybertext}