Telecommunications is the movement of information between two devices over a distance

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• 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

Chapter 6Information Technology in Business:Telecommunications and Networks

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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

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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)

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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)

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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

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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

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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

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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

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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

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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

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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

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(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)

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(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)

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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.

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Channels and Media

Figure 6.7 Characteristics of channel media

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Bandwidth and Media

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Transmission Speed

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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

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(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

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Location of a Multiplexor

Figure 6.9 Multiplexing

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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

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(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)

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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

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Network Topology

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Types of Network (Geographic Scope)

• Local networks

– PBX

– LANs

• Large networks

– WANs

– VANs

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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)

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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

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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

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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

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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

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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)

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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)

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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

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Data Communications (Cont.)

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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

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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

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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

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Communication Modes

Figure 6.4 Synchronous transmission

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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

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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

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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

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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