Transcript Communications Starting Along the Information Highway

Communications
Starting Along the
Information Highway
Yuh-Jzer Joung
Communications
Communications and the Cyberspace
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Communications (telecommunications) is the electronic transfer of
information from one location to another.
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Connectivity refers to the ability to connect devices by
communications technology to other devices and sources of information.
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“Cyberspace,” coined by William Gibson in his novel Neuromancer
to refer to a futuristic computer network that people use by plugging
their brains into it, has come to mean the computer online world and the
Internet in particular, and the whole wired and wireless world of
communications in general.
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Telephone-related communications services
Fax messages
 Dedicated fax machines
 Fax modems
 Voice mail
 analog signal → digital signal → analog signal
 E-mail (Electronic mail)
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Video/voice communication
Videoconferencing & V-mail (video mail)
Picture phones
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Communications
Online Information Service
Service:
 People connections--email, bulletin
boards, chat room
 Research and news
 Games,entertainment,clubs
 Travel services
 Downloading
 Shopping
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Communications
Three big companies:
 America Online (AOL)
 CompuServe
 Prodigy
Bulletin board systems (BBSs)
An electronic bulletin board (BBS) is a centralized information source and
message-switching system for a particular computer- linked interest group.
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The Internet
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The internet the world biggest networks, uses a protocol called TCP/IP
to allow computer to communicated.
TCP/IP, for Transmission Control Protocol/internet Protocol, is the
standardized set of guidelines (protocols) that allow different computers
on different networks to communicate with each other efficiently.
Applications over the Internet:e-mail, FAQ files, FTP, Archie, telnet,
gopher, WAIS, Web browsers.
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Internet Addresses
Domain Name system
[email protected]
country
User ID
domain
at
domain type
subdomain
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Communications
Features of the Internet
 E-mail
 Usenet newsgroups-electronic discussion groups
 Mailing lists: E-mail-based discussion groups
 FTP: for copying all the free files you want
 Telnet : to connect to remote computers
 Gopher: including Veronica and Jughead :
 WAIS: ways of searching by content
 World Wide Web: for multimedia and hypertext information retrieval
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Communications
Shared resources
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Workgroup Computing & Groupware: Workgroup computing
(collaborative computing) enables teams of co-workers to use
networks of microcomputers to share information and cooperative
projects. Groupware is a software that allows two or more people on a
network to work on the same information at the same time. Two
popular groupware:
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Lotus Notes (purchased bu IBM in 1995)
Microsoft Exchange Server
Electronic Data Interchange (EDI): EDI is the direct electronic
exchange between organizations’ computer systems of standard
business documents such as purchase orders, invoces, and shipping
documents.
Intranets: Intranets are internal corporate networks that use the
infrastructure and standards of the Internet and the WWW.
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Communications
A Security Program: Firewall
Intranet
Internet
Firewall
A firewall is a security program that connects the intranet to external
networks such as the Internet. It blocks unauthorized traffic from
entering the intranet and can also prevent unauthorized employees
from accessing the intranet.
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Communications
Portable Work : Telecommuting and virtual office
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Telecommuting: working at home with computer and
communications connections between office and home.
Virtue office: a nonpermanent and mobile office run with computer
and communications technology.
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Information or Internet appliance
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The TV/PC (picture)
The multifaceted Net
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Telephone on the Net (e.g., internet phone)
Radio on the Net (e.g., Real Audio)
Television on the Net (e.g., Real Video)
3-D on the Net (e.g., VRML)
The information/Internet appliance
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Set-top box Internet PCs
Network PDAs
Network Computers
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Communications
Modems
 Why needs a modem?
 How modems work?
 External modem vs internal modem
 Transmission speed (e.g., 9600, 14,400, 28,800, 56K bps)
bps: bits per second
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Review of analog and digital signals
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Communications
Modifying an Analog Signal
Frequency Modulation
Amplitude Modulation
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How modems work ？
Demodulate
(converts analog signals
back to digital form)
Modulate (converts digital
pulses to analog form)
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Communications
ISDN lines & Cable modems
 ISDN (Integrated Services Digital Network)
 Cable modems
How long it takes to send a 1-megabyte
Standard phone modem, 28.8 kbps
4.6 minutes
ISDN line, 64-128 kbps
2.1 minutes or less
Cable modem, 3000 kbps or less
2.6 seconds or less
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Communications
Communications software
 Error correction: Noise is anything that causes distortion in the
signal when it received.
 Data compression: Data compression reduces the volume of data
in a message, thereby reducing the amount of time required in
transmission.
 Remote control: Remote-control software allows you to control a
microcomputer from another microcomputer in a different location.
 Terminal emulation: Terminal emulation software allows you to use
your microcomputer to simulate a mainframe’s terminal.
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Communications
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The electromagnetic spectrum
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The Conduits of Communications
Twisted-pair wire
 Coaxial cable
 Fiber-optic cable
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Microwave and satellite systems
Other wireless communications
Communications
Microwave & Satellite Systems
Satellite systems
Microwave systems
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Communications
Other Wireless Communication
 One-way:
 The Global Positioning systems (GPS)
 Pagers
 Two-way:
 Analog cellular
 packet radio
 Cellular Digital Packet Data
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Communications
Cellular
connections
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Communications
The next generation of wireless communications
 Digital cellular phone
 Personal communications services
 Specialized mobile radio
 Satellite-based systems
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Type of network
 Wide area network (WAN)
 Metropolitan area network (MAN)
 Local area networks (LANs)
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Advantages of networks
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Sharing of peripheral devices
Sharing of programs and data
Better communications
Security of information
Access to databases
Communications
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Client/server LAN
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Peer-to-peer LAN
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Components of a LAN
 Connection or cabling system:
 Microcomputers with interface cards: A network interface card,
which is inserted into an expansion slot in a microcomputer,
enables the computer to send and receive messages on the LAN.
 Network operating system: e.g., Novell’s NetWare.
 Other shared devices
 Bridges and gateways: A bridge is an interface that enables
similar networks to communicate. A gateway is an interface that
enables dissimilar networks to communicate, such as a LAN with a
WAN.
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Communications
Factors Affecting Data Transmission
 Transmission rate: frequency, bandwidth
 Line configurations: point-to-point vs. multipoint.
 Serial & parallel transmission
 Direction of transmission: simplex, half-duplex, full-duplex.
 Transmission mode: asynchronous vs. synchronous.
 Packet switching: A packet is a fixed-length block of data for
transmission. Packet switching is a technique for dividing electronic
messages into packets for switching.
 Multiplexing: Multiplexing is the transmission of multiple signals over
a single communications channel. A multiplexer is a device that
merges several low-speed transmissions into one high-speed
transmission.
 Protocols: A protocol is a set of conventions governing the exchange
of data between sender and receiver in a communication network.
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Communications
Transmission mode
 Asynchronous transmission
 Synchronous transmission
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Some topologies of LANs
Star
Ring
Others:
 Hybrid network
 FDDI (Fiber Distributed Data Interface) network
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Bus
Controversial material & Censorship
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Filtering software
Browsers with ratings
The V-chip
Communications
Cyberethics
 Netiquette (Net etiquette)
 Controversial Material
 Censorship
:-)
 Privacy Issues
:-(
:-O
:-/
;-)
Happy face
Sorrow or frown
Shock
Sarcasm
Wink
:--)% Boy on a skateboard
$%...!@#!
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Communications