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Chapter 6 Information Technology in Business: Telecommunications and Networks. Telecommunications is the movement of information between two devices over a distance Information includes data, audio, video, graphics
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Chapter 6Information Technology in Business:Telecommunications and Networks • Telecommunications is the movement of information between two devices over a distance • Information includes data, audio, video, graphics • Networks are collections of devices (nodes) that can engage in telecommunications
1. Four Basic Improvements Telecommunications brought to Business • Telecommunications has improved business in four main ways: • Better communication • Higher efficiency • Better distribution of data • Instant transactions • Modern business could not be conducted without telecommunications
2. Home Networks • Connecting to the Internet from home • Dialup connection with a modem • Digital Subscriber Line (DSL) • Cable connection from a cable TV company • Satellite connection • Fixed wireless • The middle three connections are referred to as broadband connections because of their high speed and ability to carry multiple channels simultaneously (e.g., voice and data)
Dialup Modem Connection • Requires a telephone modem, network software, and Internet service provider (ISP) • Uses the phone line to connect to the Internet • Ties up the phone line while on the Internet; no incoming or outgoing calls • Slowest type of connection (56 KBPS)
DSL Connection • Requires a DSL modem, network software, and within a specified distance from a phone company installation • Often the phone company is the ISP (BellSouth) • Internet access is through the telephone line • Information traveling over the phone line can be split so that voice communication is not disrupted (you don’t need a separate phone line for your Internet connection) • Speeds range from 128 KBPS – 1500 KBPS • Line is not shared (security) and always on • Various forms of DSL
Cable Connection • Requires a cable modem, software, and access to cable TV provider • Receive information from the cable connection send information via phone line; Newer systems use cable for both directions • Cable modem separates TV signals from Internet data • Speeds are comparable to DSL speeds • Always-on connection • Not private since information is shared over the cable connection into your neighborhood; transmission speeds diminish with many users
Satellite Connection • Requires a satellite modem, software, satellite dish, and satellite provider • Receive information from the satellite connection, sends information via phone line; Newer systems use satellite for both directions • Receiving speeds 200 KBPS-400 KBPS • Same company that offers DirectTV offers DirectPC
Fixed Wireless • Alternative where cable or DSL is not available • Customer must install a microwave transceiver on roof (no wiring required) • Repeaters (from the telecom provider) pick up signals and transmit them to a base station • Transmission rates range from 2 Mbps to 100 Mbps • Growing market
3. Business Networks • Why network? Sharing • Hardware, software, and files • Communication and collaboration applications • Client/Server networks are networks in which one or more computers are servers and provide services to other computers called clients. • Servers are usually powerful computers with large storage systems (high end PC or minicomputer) • Clients are usually PCs or laptops • Print servers, file servers, Web servers
Client-Server Applications • Client-server networks are examples of distributed processing because the processing for a given application is split between the server and client • Types of processing in an application • Processing for presentation of information (user interface) • Processing of logic or business rules (calculations) • Processing related to data management (storing and retrieving data) • Several ways that this processing is split
4. Telecommunications Systems Components • Computers to process information • Terminals that send or receive data • Communications channels that carry the data between the devices in the network (channels use different media) • Communications processors that perform specific tasks in the transmission process • Communications software which controls input and output activities and other functions
(1) Computers and Channels • Channels are the links over which data are transmitted from one node to another • Data moves through the channel in the form of electromagnetic signals or pulses of light • Computer signals are digital • Parts of the telephone network require analog signals • Conversion of the signals (modems) • Media that provide channels • wire • wireless (electromagnetic spectrum)
(2) Mediums for Channels • Wire mediums • twisted pair • coaxial cable • fiber optic (each strand carries one signal) • Next generation optical networks (multiple data streams over a single strand) • Wireless transmissions • terrestrial microwave • satellite microwave (GEO) • low-orbit satellites (LEO)
Characteristics of Communication Channels • Transmission speed through a medium is measured in bits per second (BPS) • The frequency of a signal is the number of times a signal makes a complete cycle in a given time period. If the time period is one second, then the frequency is measured in Hertz (Hz). • The greater the frequency of a signal the higher the transmission speed. Conversely high transmission speeds require higher frequencies.
Figure 6.7 Characteristics of channel media Channels and Media
Sample Calculations • Suppose you wanted to download the movie Jurassic Park. In compressed form it would contain about 4*109 bytes or 32*109 bits. If you had a typical 28.8 Kbps modem, how long would it take to download the movie? • Answer: 32*109 bits/ 28.8*103 bits/sec = 1.11*106 sec or = 1.11*106 sec/3.6* 103 sec/hour = 926 hours or = 926 hours/ 24 hours/day =12.86 days
(3) Components: Special Communication Processors • Front-end processor - a special computer that manages the communications tasks for the host • Controller - a device that supervises communications between the CPU and other peripheral devices (terminals and printers) in a network • Multiplexor - a device that enables a single communications channel to carry data signals from multiple sources simultaneously • All of these devices can be considered special purpose computers
Figure 6.9 Multiplexing Location of a Multiplexor
Other Networking Hardware • Network Interface Card - a circuit board required by any device that will connect to a network (wired or wireless) • Hub – device used to connect several devices to a network • Switch – a more intelligent hub • Bridge – a device for connecting two dissimilar networks (a LAN to the Internet) • Router – a more intelligent bridge
(4) Components: Communications Software • Special software is required for telecommunications; it resides in the host, front-end processor, or other special processors • Communications software for the PC at home • Systems software (for networks) • network operating systems (NOS) • security software • Network management software • Application software for networks • Email software • Client/server applications (FrontPage)
5. Types of Networks (Topology) • Star -central host, all communication must pass through the host • Ring - all computers are linked by a closed loop; data passes from one node to the next in one direction; no central host • Bus - a single circuit links a number of devices; data is broadcast to the entire network; if one machine fails none of the other machines are effected • Tree – consists of several stars connected to form a tree
Types of Network (Geographic Scope) • Local networks • PBX • LANs • Large networks • WANs • VANs
Local Networks: PBX • A PBX (Private Branch Exchange) is special purpose computer designed to do the switching for a firm’s internal phone network • Modern PBX can carry both voice and data • Advantages - no special wiring, expandable, vendor support • Disadvantages - limited geographic scope, cannot handle high volumes of data (e.g., video)
Local Networks: LANs • Local area network - a network that requires its own cabling and encompasses a limited distance (one or two buildings); nodes are usually PCs and peripherals • Advantages • handle high volumes of data • sharing of hardware, software, files, and data • unique application (email, video conferencing, on-line applications) • Disadvantages • expandability • vendor support or internal expertise
Large Networks: WAN • Wide area networks nodes • Corporations can build their own or using communications service providers • Switched and dedicated lines • Individual firm assumes significant role in telecommunications management
Large Networks: VANs • Value-added networks are private data-only networks that provide economies in service cost and network management because they are used by many firms • Value-added means that customers do not have to invest in network equipment and management • Disadvantage • loss of control/expertise • Security • General Electric is a company that provides a VAN • An example of a Web based EDI product
Virtual Private Network • A combination of private and public lines offered by a telecom provider to allow customers, employees, and suppliers to access a firm’s private network (intranet) via the Internet. Use of a VPN creates an “extranet.” • The link between the private network and the Internet is often referred to as a tunnel • “Virtual” refers to the illusion that the use is accessing a private network directly. • Heavily used in supply chain management
6. Protocols • Protocols are rules and procedures (virtually languages) that govern the transmissions between components (devices) in a single network or between two networks • Important protocols • TCP/IP (Internet protocols) • HTTP (Internet protocol) • Ethernet (LAN protocol) • Token passing (LAN protocol) • ANSI X12 and EDIFACT (EDI protocols) • Open systems interconnection or OSI (WAN protocol)
7. Characteristics of Telecommunication Signals and Network Capabilities • Serial versus parallel • Directions of signals (simplex, half-duplex, full duplex) • Types of signals (analog versus digital) • Timing of signal transmissions (asynchronous versus synchronous) • Switching techniques (circuit and packet switching)
Serial Versus Parallel Transmissions • In serial transmissions one bit is transmitted after another in a stream of bits over a single line • On PCs modems and mice use serial transmission • Serial ports • In parallel transmissions more than one bit is transmitted simultaneously (usually an entire byte is transmitted along a bundle of parallel lines) • On PCs information sent to your printer employs parallel transmissions • Parallel ports
Three Modes of Communication Between Devices • Simplex • One-way in one direction • Radio and television • Half-Duplex • One-way in two directions • Walkie-Talkie, CB radio • Older connections between terminals and computers • Full-Duplex • Both device can transmit and receive simultaneously • Telephones • Communication between modern computers
Analog vs. Digital Signals • Analog signals • A continuous series of waves • Like a sine curve • Digital signals • A series of discrete bits • Modulation is the transformation of digital signal to an analog signal • Demodulation is the transformation of an analog signal to a digital signal • Role of a modem
Timing of Communication Between Devices • In asynchronous communication data is transmitted in a serial manner without concern of a special timing aid (clock). Most communication between computers and devices is asynchronous -- it can occur at any time and at irregular intervals. • Overhead bits: start, stop, and parity bits • In synchronous communication, transmissions between devices are governed by a timing device. Large blocks of bits can be transmitted at regular time intervals. Communications within the CPU and memory are usually synchronous. • Much lower overhead but requires expensive timing devices
Figure 6.4 Synchronous transmission Communication Modes
8. Switching Techniques • Circuit switching sets up a dedicated path between two points in a network. For the duration of the communication no other transmissions may use this circuit and all transmissions follow the dedicated path. • The telephone system links together media segments to create a single unbroken line for each telephone call. • Not very efficient for large volumes of data • In packet switching all data are packaged into fixed-sized packets that make their way to the destination over many different paths. • The Internet uses packet switching • Very efficient for sending large amounts of data • New Internet protocols will make the Internet viable for telephone calls
9. Wireless Technologies • Wireless technologies are of interest to business because they eliminate the need for expensive cables and enable mobility • Wireless standards (or Wi-Fi) apply to mobile devices (laptops, PDA, cell phones) • Family of standards IEEE 802.11 (the 11 stands for the max bit rate supported, 11 Mpbs) • Most popular is 802.11b which operates in the 2.4-2.5 GHz range • Enables spread spectrum communication (the transmitting device transmits over several frequencies so that if one degrades you can switch to another • Transmission range is about 300 ft (distance is likely to increase) • To make a device wireless requires that the device contain a wireless card
Wireless Networks • In order to communicate with a network using a wireless device, you must be close enough to an access point (AP). The access point is a device that is connected to a wired network. • If a household has a wired connection to the Internet (cable or DSL) then wireless devices can access the Internet by acquiring a wireless router (an AP) that is connected to your cable or DSL modem. This enables all your wireless devices to link to the Internet. • Public access points are often called hotspots. Winthrop has several hotspots on campus • Cell phones with dual circuitry
Other Wireless Issues • Wi-Fi networks are much cheaper to install than stationary LANS • Wi-Fi networks can be extended by adding additional access points • Wi-Fi networks are susceptible to interference from other devices • Bluetooth is another wireless networking standard for creating small private networks • The Wi-Fi standard (802.11b) is easily penetrated by outsiders with appropriate hardware and software