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Communications Starting Along the Information Highway

Communications Starting Along the Information Highway. Communications and the Cyberspace. Communications (telecommunications) is the electronic transfer of information from one location to another.

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Communications Starting Along the Information Highway

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  1. CommunicationsStarting Along theInformation Highway Communications

  2. Communications and the Cyberspace • Communications (telecommunications) is the electronic transfer of information from one location to another. • Connectivity refers to the ability to connect devices by communications technology to other devices and sources of information. • “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. Communications

  3. Telephone-related communications services • Fax messages • Dedicated fax machines • Fax modems • Voice mail • analog signal → digital signal → analog signal • E-mail (Electronic mail) Communications

  4. Video/voice communication • Videoconferencing & V-mail (video mail) • Picture phones Communications

  5. Online Information Service • Service: • People connections--email, bulletin boards, chat room • Research and news • Games,entertainment,clubs • Travel services • Downloading • Shopping Three big companies: • America Online (AOL) • CompuServe • Prodigy Communications

  6. 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. Communications

  7. The Internet 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. Communications

  8. Domain Name system aeinstein@phy.princeton.edu.us country domain User ID at domain type subdomain Internet Addresses Communications

  9. 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 Communications

  10. Shared resources • 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: • 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. Communications

  11. Intranet Internet Firewall A Security Program: 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. Communications

  12. Portable Work : Telecommuting and virtual office 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. Communications

  13. Information or Internet appliance • The TV/PC (picture) • The multifaceted Net • 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 • Set-top box Internet PCs • Network PDAs • Network Computers Communications

  14. 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 Communications

  15. Review of analog and digital signals Communications

  16. Frequency Modulation Modifying an Analog Signal Amplitude Modulation Communications

  17. How modems work ？ Modulate (converts digital pulses to analog form) Demodulate (converts analog signals back to digital form) Communications

  18. ISDN lines & Cable modems • ISDN (Integrated Services Digital Network) • Cable modems Communications

  19. 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. Communications

  20. Communications

  21. Communications

  22. The electromagnetic spectrum Communications

  23. The Conduits of Communications • Twisted-pair wire • Coaxial cable • Fiber-optic cable • Microwave and satellite systems • Other wireless communications Communications

  24. Microwave systems Microwave & Satellite Systems Satellite systems Communications

  25. One-way: The Global Positioning systems (GPS) Pagers Two-way: Analog cellular packet radio Cellular Digital Packet Data Other Wireless Communication Communications

  26. Cellular connections Communications

  27. The next generation of wireless communications • Digital cellular phone • Personal communications services • Specialized mobile radio • Satellite-based systems Communications

  28. Type of network • Wide area network (WAN) • Metropolitan area network (MAN) • Local area networks (LANs) Communications

  29. Advantages of networks • Sharing of peripheral devices • Sharing of programs and data • Better communications • Security of information • Access to databases Communications

  30. Communications

  31. Client/server LAN Communications

  32. Peer-to-peer LAN Communications

  33. 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. Communications

  34. Factors Affecting Data Transmission • Transmission rate: frequency, bandwidth • Line configurations: point-to-pointvs. multipoint. • Serial & parallel transmission • Direction of transmission: simplex, half-duplex, full-duplex. • Transmission mode: asynchronousvs.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. Communications

  35. Transmission mode • Asynchronous transmission • Synchronous transmission Communications

  36. Some topologies of LANs Star Ring Bus Others: • Hybrid network • FDDI (Fiber Distributed Data Interface) network Communications

  37. Controversial material & Censorship • Filtering software • Browsers with ratings • The V-chip Communications

  38. Netiquette (Net etiquette) Controversial Material Censorship Privacy Issues Cyberethics :-) Happy face :-( Sorrow or frown :-O Shock :-/ Sarcasm ;-) Wink :--)% Boy on a skateboard $%...!@#! Communications

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