Telecommunications Infsy 540 Dr. Ocker Chapter 7: Telecommunications, the Internet, and Information System Architecture First Edition Foundations of Information Systems Vladimir Zwass Irwin/McGraw-Hill © The McGraw-Hill Companies, Inc.., 1998 Telecommunications What is telecommunications? Telecommunications communication of information by electronic means, usually over some distance Telecommunications need to understand the – capabilities – costs, – benefits of alternative communications technologies and how to maximize their benefits for their organizations information superhighway high-speed digital telecommunications networks that are national or worldwide in scope and accessible by the general public a web of high-speed digital telecomm. networks delivering information, education, and entertainment services to offices and homes virtually eliminates the barriers of time and place information superhighway most well-known implementation of the info. superhighway is the Internet telecommunication system collection of compatible hardware and software arranged to communicate information from one location to another can transmit – – – – text graphic images voice video Telecommunications system components 1. computers to process info 2. terminals (or any input/output devices) to send and receive data 3. communications channels – links by which data or voice are transmitted between sending and receiving devices in a network Telecommunications system components 4. communications processors provide support functions for data transmission and reception; – e.g. modems, multiplexes, controllers, front-end processors 5. communications software - controls input and output activities and manages other functions of network Functions of telecommunications systems transmission of information establishes the interface between sender and receiver routes messages along most efficient paths performs processing of information to ensure that the right message gets to the right receiver Functions of telecommunications systems performs editing of data checks for errors converts messages from one speed to another e.g. from speed of computer to speed of communications line controls flow of information Protocols telecomm. network contains diverse hardware and software components that need to work together to transmit information Protocols different components in a network can communicate by following a common set of rules that allows them to “talk” to each other protocol - set of rules and procedures that govern transmission between components in a network principal functions of protocols to identify each device in the communication path to secure the attention of the other device to verify correct receipt of the transmitted message to verify that a message requires retransmission because it cannot be correctly interpreted to perform recovery when errors occur Types of signals: analog and digital information travels through a telecommunications system in form of electromagnetic signals signals represented in 2 ways - analog and digital Types of signals: analog and digital analog signal - continuous waveform that passes through a communications medium – used for voice communications digital signal - discrete waveform that transmits data coded into 2 discrete states as 1-bits and 0-bits, which are represented as on-off electrical impulses – used for data communications Types of signals: analog and digital if a telecommunications system is set up to process analog signals - a digital signal cannot be processed without some alterations all digital signals must be translated into analog signals before they can be transmitted in an analog system Modems modem - modulate/demodulate translates the digital signals of computer into analog form for transmission over ordinary telephone lines, or translates analog signals back into digital form for reception by a computer Telecommunications over a Telephone Line Digital Computer Modem Analog Telephone Link Digital Modem Computer communication channels means by which data are transmitted from one device in a network to another links by which data or voice are transmitted between sending and receiving devices in a network Types of communications channels a channel can utilize different kinds of telecomm. transmission media: – twisted wire – coaxial cable – fiber optics – terrestrial microwave – satellite – radio (wireless) transmission twisted wire pairs of twisted copper wires phone lines coaxial cable thickly insulated copper wire used for cable TV fiber optic cable consists of thousands of strands of clear glass fiber – thickness of human hair fast, light, and durable data transmitted as light impulses Radio (wireless) transmission sends signal through air or space without any physical tether e.g. cellular radio systems used for mobile telephones microwave high-volume long-distance, point-topoint transmission high-frequency radio signals are transmitted through atmosphere from one terrestrial transmission station to another transmission only in straight line satellites serve as relay stations for microwave signals use to transmit large amounts of data over long distances LANS (local area networks) cover limited distance – usually one building or several buildings in close proximity require their own communications channels allow orgs. to share hardware and software many applications require high-capacity networks – e.g. email, graphics, video conferencing LANS used to link PCs within a building to share information and peripheral devices – e.g. laser printers Servers computer in a network that stores various programs and data files for users of a network; determines access and availability in the network contains the LANS’ network operating system – manages the server – routes and manages communications on the network Gateway network gateway - connects the LAN to public networks (e.g. telephone network, other corporate networks) can connect dissimilar networks by translating from one set of protocols to another LAN technology consists of cabling – twisted wire, coaxial, or fiber optic or wireless technology that link computers and software to control LAN activities main disadvantage of LAN Inflexible – need new wiring each time the LAN is moved Wide-area Networks cover broad geographical distances – ranging from several miles to across continents may consist of a variety of cable, satellite, and microwave technologies common carriers - licensed by government to provide communications services to public (e.g. AT&T, MCI) Wide-area Networks can consist of combination of switched and dedicated lines switched lines – telephone lines that can be used for data transmission – call is routed or switched through paths to destination dedicated line – continuously available for transmission – can be leased or purchased from common carriers A Wide Area Network Mainframe (Headquarters) Minicomputer (Division A) LAN Minicomputer (Division B) LAN Minicomputer (Division C) ... Local Workstations (Microcomputers and Other Terminals) Telecommunications Equipment in a Wide Area Network telecommunications for competitive advantage many of the strategic applications would not be possible without telecommunications firms that fail to consider telecommunication in their strategic plans will fall behind Applications – email – voice mail – fax – teleconferencing – digital information services – videoconferencing – electronic data interchange (EDI) Applications digital information services – obtain information from outside of the company instantly – e.g. stock prices, legal research, news articles etc. includes electronic bulletin boards Applications Teleconferencing – allows groups of people to confer simultaneously via telephone or electronically (computer conferencing) videoconferencing – teleconferencing with a view Applications EDI - electronic data interchange – direct computer-to-computer exchange between two organizations of standard business transaction documents such as invoices, bills, purchase orders. EDI saves money and time because transactions can be transmitted from one IS to another through telecomm. Network – eliminates printing and handling of paper at one end and inputting of data at the other The Internet & Electronic Commerce Internet Global network of computer netwokrs without a centralized control the “information superhighway” To connect to the Internet Network has to send and receive data packets using the TCP/IP protocol suite serieis of routers forwards packets to tehir destination World-wide Web (WWW) Software that organizes information on the Internet into a network of interrelated electronic documents Web is a client/server system collection of electronic sites stored on thousands of servers all over the world Electronic commerce Sharing business information, maintaining business relationships and conducting business transactions by means of telecommunications networks doing business electronically – replacing most of the paperwork and telephone work with compouter-mediated information and transaction exchange intranets Internal networks of web sites set up on corporate LANS and WANs separated from the public Internet by a firewall firewall prevents access from the Internet but allows access to the Internet