Yuh-Jzer JoungCommunications Communications Starting Along the Information Highway

Yuh-Jzer JoungCommunications 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 and the Cyberspace

Yuh-Jzer JoungCommunications Telephone-related communications services Fax messages Dedicated fax machines Fax modems Voice mail analog signal → digital signal → analog signal (Electronic mail)

Yuh-Jzer JoungCommunications Video/voice communication +Videoconferencing & V-mail (video mail) +Picture phones

Yuh-Jzer JoungCommunications Online Information Service Three big companies: America Online (AOL) CompuServe Prodigy Service: People connections-- , bulletin boards, chat room Research and news Games,entertainment,clubs Travel services Downloading Shopping

Yuh-Jzer JoungCommunications 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.

Yuh-Jzer JoungCommunications 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: , FAQ files, FTP, Archie, telnet, gopher, WAIS, Web browsers.

Yuh-Jzer JoungCommunications Internet Addresses Domain Name system User IDat subdomain domain country domain type

Yuh-Jzer JoungCommunications Features of the Internet + + Usenet newsgroups-electronic discussion groups + Mailing lists: -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

Yuh-Jzer JoungCommunications 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.

Yuh-Jzer JoungCommunications IntranetInternet 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.

Yuh-Jzer JoungCommunications 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.

Yuh-Jzer JoungCommunications Information or Internet appliance n The TV/PC (picture) n The multifaceted Net n Telephone on the Net (e.g., internet phone) n Radio on the Net (e.g., Real Audio) n Television on the Net (e.g., Real Video) n 3-D on the Net (e.g., VRML) n The information/Internet appliance n Set-top box Internet PCs n Network PDAs n Network Computers

Yuh-Jzer JoungCommunications Modems 4Why needs a modem? 4How modems work? 4External modem vs internal modem 4Transmission speed (e.g., 9600, 14,400, 28,800, 56K bps) bps: bits per second

Yuh-Jzer JoungCommunications Review of analog and digital signals

Yuh-Jzer JoungCommunications Frequency Modulation Modifying an Analog Signal Amplitude Modulation

Yuh-Jzer JoungCommunications How modems work ？ Modulate (converts digital pulses to analog form) Demodulate (converts analog signals back to digital form)

Yuh-Jzer JoungCommunications ISDN lines & Cable modems 4ISDN (Integrated Services Digital Network) 4Cable modems

Yuh-Jzer JoungCommunications Communications software 4 Error correction: Noise is anything that causes distortion in the signal when it received. 4 Data compression: Data compression reduces the volume of data in a message, thereby reducing the amount of time required in transmission. 4 Remote control: Remote-control software allows you to control a microcomputer from another microcomputer in a different location. 4 Terminal emulation: Terminal emulation software allows you to use your microcomputer to simulate a mainframe’s terminal.

Yuh-Jzer JoungCommunications

Yuh-Jzer JoungCommunications

Yuh-Jzer JoungCommunications The electromagnetic spectrum

Yuh-Jzer JoungCommunications The Conduits of Communications Twisted-pair wire Coaxial cable Fiber-optic cable Microwave and satellite systems Other wireless communications

Yuh-Jzer JoungCommunications Microwave systems Microwave & Satellite Systems Satellite systems

Yuh-Jzer JoungCommunications  One-way:  The Global Positioning systems (GPS)  Pagers  Two-way:  Analog cellular  packet radio  Cellular Digital Packet Data Other Wireless Communication

Yuh-Jzer JoungCommunications Cellular connections

Yuh-Jzer JoungCommunications The next generation of wireless communications IDigital cellular phone IPersonal communications services ISpecialized mobile radio ISatellite-based systems

Yuh-Jzer JoungCommunications Type of network 4Wide area network (WAN) 4Metropolitan area network (MAN) 4Local area networks (LANs)

Yuh-Jzer JoungCommunications Advantages of networks 4Sharing of peripheral devices 4Sharing of programs and data 4Better communications 4Security of information 4Access to databases

Yuh-Jzer JoungCommunications

Yuh-Jzer JoungCommunications Client/server LAN

Yuh-Jzer JoungCommunications Peer-to-peer LAN

Yuh-Jzer JoungCommunications Components of a LAN 4 Connection or cabling system: 4 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. 4 Network operating system: e.g., Novell’s NetWare. 4 Other shared devices 4 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.

Yuh-Jzer JoungCommunications 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.

Yuh-Jzer JoungCommunications Transmission mode 4Asynchronous transmission 4Synchronous transmission

Yuh-Jzer JoungCommunications Some topologies of LANs StarRingBus Others:  Hybrid network  FDDI (Fiber Distributed Data Interface) network

Yuh-Jzer JoungCommunications Controversial material & Censorship Filtering software Browsers with ratings The V-chip

Yuh-Jzer JoungCommunications  Netiquette (Net etiquette)  Controversial Material  Censorship  Privacy Issues Cyberethics :-) Happy face :-( Sorrow or frown :-O Shock :-/ Sarcasm ;-) Wink : -- )% Boy on a skateboard