Chapter 1 Introduction.docx

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Ryerson University
Information Technology Management
ITM 301
Franklyn Prescod

Chapter 111 Use of Computer Networks Computer Networks a collection of autonomous computers interconnected by a single technology two computers are said to be interconnected if they are able to exchange information Connection can be made via copper wire fiber optics microwaves infrared and communication satellites Distribution System a collection of independent computers appearing to its users as a single coherent system It has a single model that it presents to users with usually a layer of software middleware on top of the operating system Example World Wide Web is a distributed system which runs on top of the Internet and presents a model in which everything looks like a document web pages Distinction In computer networks the model and software are absent Users are exposed to actual machine without the machine trying to lookact in a coherent wayWhereas a distributed system is software built on top of a network The software gives a high degree of cohesiveness and transparencyThe distinction lies with the software especially the OS rather than the hardware111Business Applications Resource Sharing the goal to make all programs equipment and especially data available to anyone on the network without regard to the physical location of the resource or the user Very important is sharing information allows people to access relevant information and documents instantly Virtual Private Networks VPN networks used to join the individual networks at different sites into one extended networkBusinesses that operate many offices around the world should be able to access information as if it was local Servers powerful computers that are often centrally housed and maintained by a system administrator one server can handle a large number hundreds or thousands of clients simultaneously Clients employees have simpler machines on their desks with which they access remote data likespreadsheets basically a PC ClientServer Model The client and server machines are connected by a network example the Web Application in which the server generates web pages based on its database in response to client requests that may update the databaseTwo processes are involved communication takes the form of the client process sending a message over the network to the server process The client process then waits for a reply message When the server process gets the request it performs the requested work or looks up the requested data and sends back a reply Voice over IP VoIPIP Telephony telephone calls between employees may be carried by the computer network instead of a phone company when the internet technology is used Desktop Sharing lets remote workers see and interact with a graphical computer screen112 Home Applications Metcalfes Law Bob Metcalfe the inventor of Ethernet hypothesized that the value of a network is proportional to the square of the number of users because this is roughly the number of different connections that may be made Peer to Peer Communication individuals who form a loose group can communicate with others in the group there is no fixed division into clients and servers no central database such as emails downloading and sharing music Use of Social networking such as Facebook allows person to person communication and accessing information people use ecommerce in order to buy stuff online and have interactive visualsUbiquitous Computing computing is embedded into everyday life Mark Weiser Example home security systems fire alarms consumer electronics all are networked Power Line Networks devices such as television that plug into the wall to send information throughout the house over the wires that carry electricity RFID Radio Frequency Identification tags that are passive chip the size of stamps and can be affixed to anything It lets RFID readers locate and communicate with the items over a distance of up to several meters113 Mobile Networks Cellular Networks operated by telephone companies are one kind of wireless network that blankets us with coverage for mobile phones Wireless Hotspots another kind of wireless network for mobile computers Anyone with a laptop computer and a wireless model can be connected to the Internet through hotspot as though the computer were plugged into a wired network Distinction between a wireless network and mobile network is that if a traveler plugs a notebook computer into the wired network jack in a hotel room he has mobility without wireless networkMobile Commerce MCommerce short text messages from the mobile are used to authorize payments for food movie tickets and other small items on their mobile bill rather than cash or credit Sensor Networks are made up of nodes that gather and wirelessly relay information they sense about the state of the physical world They provide a wealth of data on behavior that could not previously be observed Mobile devices that is so small that we can even track insects114 Social Issues Views that are publicly posted may be deeply offensive to some people Opinions are not limited to text high resolution photographs and video clips are posted over computer networks Network Neutralitycommunications that are not differentiated by their content or source or who is providing the content DMCA takedown Notices warnings for copyright infringement usually from peer to peer networks Profiling private companies gain information about users by looking at the cookies small files that web browser stores on user computers which allows companies to track user activities in cyber space and know confidential information that may have leaked onto the internet Phishing Messages masquerade as originating from a trustworthy party for example your bank to try to trick you into revealing sensitive information CAPTCHAs a computer asks a person to solve a short recognition task in order to know that the person is human12 Network Hardware Criteria for Networks Transmission TechnologyBroadcast Links the communication channel is shared by all the machines on the network packets sent by any machine are received by all the others An address field within each packet
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