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Bba401 Slm Unit 03

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  • Unit 3 Network Infrastructure forE-Commerce - II

    Structure3.1 Introduction

    Objectives3.2 Common Gateway Interface3.3 Multimedia Objects3.4 Network Access Equipment3.5 Network Cables3.6 Broadband Telecommunication3.7 Summary3.8 Glossary3.9 Terminal Questions

    3.10 AnswersReferences

    3.1 Introduction

    In the previous unit, you learnt about the network infrastructure for e-commerce,including topics such as Local Area Network (LAN), Ethernet, Wide Area Network(WAN), the Internet, TCP/IP Reference Model, Domain Names, and Hyper TextMarkup Language (HTML).

    In this unit, you will learn about Common Gateway Interface (CGI), whichis a process used to share the data between the web server and the web browser.CGI is a set of standards where a program can send data back to the webserver where it can be processed. Also discussed at length is broadbandtelecommunication, which makes use of a digital or analogue signal to relayvoice and data. In most applications, the term is associated with systems offeringfast transmission of data, either using latest digital technology or an analoguesystem with a wider bandwidth. There are numerous types of broadbandtelecommunications in use today.

    You will also be taught various other topics, including, but not limited to,multimedia objects, network access equipment, and network cables.

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    ObjectivesAfter studying this unit, you should be able to:

    Evaluate the importance of common gateway interface Define and give examples of multimedia objects Demonstrate the working of network access equipment Summarize the functioning of network cables Discuss the importance of broadband telecommunication

    3.2 Common Gateway Interface

    As you traverse the vast frontier of the WWW, you could come across documentsthat make you wonder, How did they do this? These documents could consistof, among other things, forms that put for advice or registration information,image maps that allow you to click on different parts of the image, counters thatpresent the number of users that accessed the document, and utilities thatallow you to search databases for specific information. In most cases, youll findthat these properties were done using the Common Gateway Interface,commonly known as CGI.

    One of the Internets worst-kept secrets is that CGI is astoundingly simple.That is, its trivial in design, and anyone with an iota of programming experiencecan write rudimentary scripts that work. Its only when your requirements aremore demanding that you have to master the more complex workings of theWeb.

    CGI is the part of the Web server that can communicate with other differentprograms running on the server. With CGI, the Web server can call up a program,while passing user-specific data to the program (such as what host the user isconnecting from, or input the user has supplied using HTML form syntax). Theprogram then processes that data and the server passes the programs responseback to the Web browser.

    CGI is not an enchantment; its just programming with some particulartypes of input and a few strict rules on program output. Everything in between isjust programming. Of course, there are special techniques that are particular toCGI. But underlying it all is the simple model as shown in Figure 3.1

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    Web Browser

    Information

    HTTP Server

    3. Gateway Script of Program

    1. Form/Query 2. CGI

    4. HTML 4. HTML

    Figure 3.1 CGI Model

    Common uses of CGI include: Guest books Email forms Mailing list maintenance Blogs

    Self-Assessment Questions

    1. State whether the following statements are true or false.(a) CGI is a set of standards where a program can send data back to

    the web server where it can be processed.(b) One of the Internets worst-kept secrets is that CGI is astoundingly

    complex.

    3.3 Multimedia Objects

    Multimedia objects are files that hold images, audio recordings, videoclips and scanned documents, etc., which relate to some fact within ourgenealogical data. A multimedia object can be linked with several entities(animals, person, family, source ) and vice versa.

    In other words multimedia is media and content that uses a combinationof different content forms. The term can be used as a noun (a medium

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    with multiple content forms) or as an adjective describing a medium ashaving multiple content forms. The term is used in contrast to media whichonly use traditional forms of printed or hand-produced material. Multimediaincludes a combination of text, audio, still images, animation, video, andinteractivity content forms.

    Multimedia is usually recorded and played, displayed or accessed byinformation content processing devices, such as computerized andelectronic devices, but can also be part of a live performance. Multimedia(as an adjective) also describes electronic media devices used to storeand experience multimedia content. Multimedia is distinguished from mixedmedia in fine art; by including audio, for example, it has a broader scope.The term rich media is synonymous for interactive multimedia.Hypermedia can be considered one particular multimedia application.

    Multimedia presentations may be viewed by person on stage, projected,transmitted, or played locally with a media player. A broadcast may be alive or recorded multimedia presentation. Broadcasts and recordings canbe either analogue or digital electronic media technology. Digital onlinemultimedia may be downloaded or streamed. Streaming multimedia maybe live or on-demand.

    Multimedia games and simulations may be used in a physical environmentwith special effects, with multiple users in an online network, or locallywith an offline computer, game system, or simulator.

    The various formats of technological or digital multimedia may be intendedto enhance the users experience, for example to make it easier and fasterto convey information. Or in entertainment or art, to transcend everydayexperience. Enhanced levels of interactivity are made possible bycombining multiple forms of media content. Online multimedia isincreasingly becoming object-oriented and data-driven, enablingapplications with collaborative end-user innovation and personalizationon multiple forms of content over time. Examples of these range frommultiple forms of content on Web sites like photo galleries with both images(pictures) and title (text) user-updated, to simulations whose co-efficient,events, illustrations, animations or videos are modifiable, allowing themultimedia experience to be altered without reprogramming. In additionto seeing and hearing, Haptic technology enables virtual objects to befelt. Emerging technology involving illusions of taste and smell may alsoenhance the multimedia experience.

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    Self-Assessment Questions

    2. Fill in the blanks with appropriate words.(a) Multimedia is media and content that uses a combination of different

    ______forms.(b) Online multimedia is increasingly becoming _________ and

    _________.

    3.4 Network Access Equipment

    Hubs: All networks (except those using coaxial cable) require a central locationto bring media segments together. These central locations are called Hubs.Hubs are special repeaters that overcome the electromechanical limitations ofa media signal path.

    There are three types of Hubs:1. Passive Hub: A passive hub simply combines the signals of network

    segments. There is no signal regeneration.2. Active Hub: Active hub is that which regenerates of amplifies the

    signals.3. Intelligent Hub: Intelligent hub regenerates the signal and performs

    some network management and intelligent path selection.Switches: It supports transmitting receiving and controlling traffic with othercomputers on the network. MAC (Media Access Control) address is hard-codedon the card by manufacture. This MAC address is globally unique.Comparison of Hub and Switch

    Hub is broadcasting device while switch is point-to-point communicationdevice.

    Hub operates at physical layer while switch operates at data link layer. Switch can be used as a repeater but hub cannot be used as repeater. Switch uses switching table to find out the correct destination while hub

    simply broadcasts the incoming packet.Repeaters: Repeaters (refer to Figure 3.2) are devices that operate at thephysical layer of the OSI model. The basic purpose of a repeater is to extend

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    the distance of LAN. Their primary purpose is simply to regenerate a signalreceived from input and correct the signal to its original state for output.

    Workgroup Repeaters(Fiber to AUI ST)(LE4204A-R3)

    Pure Networking10/100 Ethernet

    Switch (LB8516A)

    Standard Ethernet Cable(LCN100)

    Duplex Fiber Optic Cable (EFN062),upto 1.2 miles (1.9 km)

    PCFigure 3.2 Repeater

    Network Interface Card (NIC): The primary function of NIC is to allow thecomputer to communicate on the network. It supports transmitting, receivingand controlling traffic with other computer on the network. NIC operates atphysical layer of OSI model. MAC address is hard coded onto the card bymanufacturer. This MAC address is globally unique and is of 48 bits. The MACaddress provides a way to distinguish one NIC from other NIC. These MACaddresses are also called physical address.Bridge: A bridge (refer to Figure 3.3) is a device that is attached to two or moreLANs to create an extended LAN. The LANs to be interconnected may be similaror dissimilar. As each type of LAN has different MAC frame structure, the bridgetakes care of these differences by reformatting the frames.

    Manufacturing Database Server

    Bridge

    Corporate LAN Segment Manufacturing SegmentFigure 3.3 Bridge

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    Router: A router (refer to Figure 3.4) operates at the third network layer of ISO-OSI model. It connects more than two different types of network. Routerdetermines the short path between source and destination for data transmission.

    WindowsSmall Business

    Server

    Client computersInternet

    Router devicewith an assigned

    IP address Switchor hub

    Figure 3.4 Router

    Table 3.1 shows the similarities and differences between a router and abridge.

    Table 3.1 Similarities and Differences between a Router and a Bridge

    Router Bridge 1 Router operates network layer of

    OSI model. Bridge operates the data link layer of OSI model.

    2 Routers are relatively expensive. Bridges are relatively inexpensive. 3 Routers are difficult to set up and

    configure. Bridges are relatively easy to configure.

    4 Routers can accommodate multiple paths.

    Bridges can accommodate single path.

    5 Routers can join two different networks.

    Bridges extend the existing networks.

    6 Routers can be both hardware and software device.

    Bridges can be both hardware and software device.

    Activity 1How much better are todays web servers compared to what was availableten years back? Refer the Internet and give a detailed answer.

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    Self-Assessment Questions

    3. State whether the following statements are true or false.(a) Switch is broadcasting device while hub is point-to-point

    communication device.(b) Routers are very cheap.

    3.5 Network Cables

    Network cables are the medium through which information generally travelsfrom one node/network device to another. There are many types of cables whichare used for computer network. In some cases, a network will utilize only onetype of cable, while other networks will use a variety of cable types. The type ofcable chosen for a network is related to the networks topology, protocol, andsize. Understanding the characteristics of different types of cable and how theyrelate to other aspects of a network is necessary for the development of asuccessful network.

    There are following types of cables used in networks and other relatedtopics.

    Fibre optic cable Cable installation guides Wireless LANs Unshielded Twisted Pair (UTP) cable Shielded Twisted Pair (STP) cable Coaxial cable

    Fibre optic cableFibre optic cabling (refer to Figure 3.5) consists of a centre glass core surroundedby several layers of protective materials. It transmits light rather than electronicsignals eliminating the problem of electrical interference. This makes it ideal forcertain environments that contain a large amount of electrical interference. It isalso the standard for connecting networks between buildings, due to its immunityto the effects of moisture and lighting.

    Fibre optic cable has the capability to transmit signals over much longerdistances than coaxial and twisted pairs. It also has the capability to carry

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    information at superior speeds. This capacity broadens communicationpossibilities to include services such as video conferencing and interactiveservices. The cost of fibre optic cabling is comparable to copper cabling; however,it is more difficult to install and modify.

    The centre core of fibre cables is made from glass or plastic fibres. Aplastic coating then cushions the fibre centre, and kevlar fibres help to strengthenthe cables and prevent breakage. The outer insulating jacket is made of teflonor PVC.

    Figure 3.5 Fibre Optic Cable

    There are two common types of fibre cables single mode and multimode.Multimode cable has a larger diameter; however, both cables provide highbandwidth at high speeds. Single mode can provide more distance, but it ismore expensive.

    Specification Cable Type 10BaseT Unshielded Twisted Pair 10Base2 Thin Coaxial 10Base5 Thick Coaxial 100BaseT Unshielded Twisted Pair 100BaseFX Fibre Optic 100BaseBX Single mode Fibre 100BaseSX Multimode Fibre 1000BaseT Unshielded Twisted Pair 1000BaseFX Fibre Optic 1000BaseBX Single mode Fibre 1000BaseSX Multimode Fibre

    Installing cablesome guidelinesWhen running cable, it is best to follow a few simple rules:

    If it is necessary to run cable across the floor, cover the cable with cableprotectors.

    Label both ends of each cable. Use cable ties (not tape) to keep cables in the same location together. Always use more cable than you need. Leave plenty of slack.

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    Test every part of a network as you install it. Even if it is brand new, it mayhave problems that will be difficult to isolate later.

    Stay at least 3 feet away from fluorescent light boxes and other sourcesof electrical interference.

    Wireless LANs

    Figure 3.6 Wireless LANs

    Wireless LANs use high frequency radio signals, infrared light beams, orlasers to communicate between the workstations, servers, or hubs. Eachworkstation and file server on a wireless network has some sort of transceiver/antenna to send and receive the data. Information is relayed betweentransceivers as if they were physically connected. For longer distances, wirelesscommunications can also take place through microwave transmission, cellulartelephone technology or by satellite.

    Wireless networks are great for allowing laptop, desktop, portable devices,or remote computers to connect to the LAN. Wireless networks are also beneficialin older buildings where it may be difficult or impossible to install cables.

    The two most common types of infrared communications used in schoolsare line-of-sight and scattered broadcast. Line-of-sight communication meansthat there must be an unblocked direct line between the workstation and thetransceiver. If a person walks within the line-of-sight while there is a transmission,the information would need to be sent again. This kind of obstruction can slowdown the wireless network. Scattered infrared communication is a broadcast ofinfrared transmissions sent out in multiple directions that bounces off walls andceilings until it eventually hits the receiver. Networking communications withlaser are virtually the same as line-of-sight infrared networks.Advantages of wireless networks:

    Cost: Setting up a wireless network can be much more cost effective thanbuying and installing cables.

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    Expandability: Adding new computers to a wireless network is as easy asturning the computer on (as long as you do not exceed the maximumnumber of devices).

    Mobility: With a laptop computer or mobile device, access can be availablethroughout a school, at the mall, on an airplane, etc. More and morebusinesses are also offering free Wi-Fi access (Hot spots).

    Fast setup: If your computer has a wireless adapter, locating a wirelessnetwork can be as simple as clicking Connect to a Networkin somecases, you will connect automatically to networks within range.

    Disadvantages of wireless networks: Inconsistent connections: How many times have you said to yourself,

    Wait a minute, I just lost my connection? Because of the interferencecaused by electrical devices and/or items blocking the path of transmission,wireless connections are not nearly as stable as those through a dedicatedcable.

    Speed: The transmission speed of wireless networks is improving;however, faster options (such as gigabit Ethernet) are available via cables.If you are only using wireless for Internet access, the actual Internetconnection for your home or school is generally slower than the wirelessnetwork devices, so that connection is the bottleneck. If you are alsomoving large amounts of data around a private network, a cabledconnection will enable that work to proceed much faster.

    Security: Protect sensitive data with backups, isolated private networks,strong encryption and passwords, and check network access traffic toand from the wireless network.

    Interference: Because wireless networks deploy radio signals and similartechniques for transmission, they are vulnerable to intrusion from lightsand electronic devices.

    Unshielded Twisted PairTwisted pair cabling comes in two varieties: shielded and unshielded. Unshieldedtwisted pair (UTP) is the most popular and is generally the best option for schoolnetworks.

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    Figure 3.7 Unshielded Twisted Pair

    The quality of UTP (refer to Figure 3.7) may range from telephone-gradewire to extremely high-speed cable. This cable has four pairs of wires inside thejacket. Each pair is twisted with a different number of twists per inch that helpsto eliminate interference from adjoining pairs and other electrical devices. TheElectronic Industry Association/Telecommunication Industry Association(EIA/TIA) has set standards of UTP and rated six categories of wire, which areas follows.

    Category Speed Use 1 1 Mbps Voice Only (Telephone Wire) 2 4 Mbps Local Talk & Telephone (Rarely used) 3 16 Mbps 10BaseT Ethernet 4 20 Mbps Token Ring (Rarely used)

    100 Mbps (2 pair) 100BaseT Ethernet 5 1000 Mbps (4 pair) Gigabit Ethernet

    6 1,000 Mbps Gigabit Ethernet 7 10,000 Mbps Gigabit Ethernet

    Unshielded Twisted Pair connectorThe standard connector for unshielded twisted pair cabling is known as RJ-45connector (refer to Figure 3.8). This is a plastic connector that looks like a largetelephone-style connector. A slot allows the RJ-45 to be inserted only one way.RJ stands for Registered Jack, implying that the connector follows a standardborrowed from the telephone industry. This standard assigns which wire goeswith each pin inside the connector.

    Figure 3.8 RJ-45 Connector

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    Shielded Twisted Pair (STP) cableUTP cable is the least expensive cable; it may be disposed to radio and electricalfrequency interference (it should not be too close to electric motors, fluorescentlights, etc.). If you must place cable in environments with lots of potentialinterference, or if you must place cable in extremely sensitive environmentsthat may be susceptible to the electrical current in the UTP, shielded twistedpair may be the solution. Shielded cables can also facilitate to extend themaximum distance of the cables.

    Shielded twisted pair cable is available in three different configurations:1. Each pair of wires is individually shielded with foil.2. There is a foil or braid shield inside the jacket covering all wires.3. There is a shield around each individual pair, as well as around the

    entire group of wires.Coaxial cableCoaxial cable (refer to Figure 3.9) has a single copper conductor at its centre. Aplastic layer provides insulation between the centre conductor and a braidedmetal shield. The metal shield facilitates to block any outside interference fromfluorescent lights, motors, as well as other computers.

    Figure 3.9 Coaxial Cable

    Coaxial cabling is not easy to install, but it comes with the advantage ofbeing highly resistant to signal interference. Also, it can support greater cablelengths between network devices than twisted pair cable. The two types ofcoaxial cabling are thick coaxial and thin coaxial.

    Thin coaxial cable is known as thinnet. 10Base2 refers to the specificationsfor thin coaxial cable moving Ethernet signals. The 2 refers to the approximatemaximum segment length being 200 metres. The maximum division length isactually 185 metres. Thin coaxial cable has been popular in school networks,particularly linear bus networks.

    Thick coaxial cable is known as thicknet. 10Base5 refers to thespecifications for thick coaxial cable carrying Ethernet signals. The 5 refers tothe maximum division length being 500 metres. Thick coaxial cable has anextra protective plastic cover that helps keep moisture away from the centre

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    conductor. This creates thick coaxial a great choice when running longer lengthsin a linear bus network. One disadvantage of thick coaxial is that it is not easilybendable and quite difficult to install.

    Coaxial cable connectorsA most common type of connector used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector (refer to Figure 3.10). There are different types ofadapters for BNC connectors, including a T-connector, barrel connector, andterminator. Connectors are the most vulnerable points in any network. To helpavoid problems, always use the BNC connectors that screw onto the cable.

    Figure 3.10 BNC Connector

    Self-Assessment Questions

    4. State whether the following statements are true or false.(a) Coaxial cabling is extremely easy to install.(b) One of the rarest forms of connectors is the Bayone-Neill-Concelman

    (BNC) connector.5. Fill in the blanks with appropriate words.

    (a) Fibre optic cabling consists of a centre _____ core surrounded byseveral layers of protective materials.

    (b) The standard connector for unshielded twisted pair cabling is knownas _______connector.

    3.6 Broadband Telecommunication

    In general, broadband refers to telecommunication where a wide band offrequencies is available to transmit information. There is wide range offrequencies available, and information can be multiplexed and sent on manydifferent frequencies or channels within the band simultaneously. This way, more

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    information can be transmitted in a shorter duration of time than what isachievable with older methods of transmission.

    One of the configurations that have been around for a number of years isthe integrated services digital network, or ISDN. This network design can beused to relay voice and data over copper telephone lines. This may not be thefastest option in fashion today; however, it does make it possible to access theInternet without the requirement of a high-speed connection or a lot of resources.

    Another common example is the asynchronous transfer mode, referredto in the telecommunications world as ATM. This option is much quicker thanISDN and has proven to be extremely handy for companies relying heavily onthe Internet and electronic communications.

    Asynchronous Transfer Mode, (ATM), is a network technology based ontransferring data in cells or packets of a fixed size. The cell used with ATM issmaller compared to units used with older technologies. This size of the cellallows for an advantageATM equipment can transmit video, audio, andcomputer data over the same network, and guarantee that no single type ofdata clutters the line.

    Some people opine that ATM is the definitive answer for the Internetbandwidth problem; others and not so confident. ATM creates a fixed or routebetween two points whenever data transfer begins. This differs from TCP/IP,where messages are divided into packets and each packet can take a differentroute from source to destination. This difference makes it easier to track and billdata usage across an ATM network, but it renders it less adaptable to suddenincreases in network traffic.

    Integrated Service Digital NetworkIntegrated Service Digital Network, (ISDN), is the original high-speed Internetservice. It sparked the high-speed Internet development between serviceproviders during the 1990s and, of course, revolutionized Internet use. Muchlike its predecessor, the dial-up Internet service, ISDN utilizes a phone line. Infact, it set the standard for telephone data service.

    ISDN Internet service was the improvement upon dial-up, and it also pavedthe way for DSL and cable-modem Internet service thereafter. It can beconsidered the step of Internet evolution that lies between dial-up and DSL/Cable. Modernizing Internet use and bringing high-speed access inside thehome, ISDN became the standard by which rival broadband Internet serviceproviders competed. Although ISDN Internet service still exists, like the dial-up

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    connection it is being replaced by faster and cheaper services that the broadbandcompanies are providing. Regardless, broadband high-speed Internet serviceis still compared with ISDN today, since they both represent the benchmark oftheir times.

    ISDN Internet service is basically a telephone-based network system thatoperates by a circuit switch, or dedicated line, and is capable of transmittingdata and phone conversations digitally over normal telephone wires. This makesit both faster and of higher quality than dial-up Internet service. During the 1990sthis revolutionized the way people did business. No longer would you have tomiss a call in order to access your Internet, or shut down the Internet to make atelephone call. As such, ISDN Internet service made video teleconferencing notonly possible, but very popular as well.

    There are two different types, or lines, of ISDN Internet service. The first is a basic rate ISDN line. Called a Basic Rate Interface

    (BRI), this line has two data, or bearer, channels that operate at 64kbit/sec. Two or more ISDN-BRI lines can be combined as well,yielding speeds of 256 kbit/sec. It is common to combine these linesfor video conferencing use or for transmitting data at higher speeds.

    The second type of ISDN line is called a primary rate line, or PrimaryRate Interface (PRI). This line had 23 bearer channels and has atotal speed of 1,544 kbit/sec. It is used mostly for telephonecommunication rather than data transmission, particularly withincompanies that have large, private telephone exchange systemsoperating inside their business.

    The advantages of having ISDN Internet service definitely lies in the datalines themselves. Not only do you have constant data speed via these lines,each bearer channel runs at 64 kbit/sec with the ability to be combined to reachgreater speeds. ISDN Internet serviced also facilitates multiple data transmission,so telephone calls and data downloading are no longer mutually exclusive. Thedisadvantages, however, is that the digital clarity of ISDN voice communicationand its speedy data transmission come at an extra cost. ISDN is billed like aphone line, but with an extra cost for service. Although its operational distancefrom the ISDN central office is greater than that for DSL, its terminal adaptor(similar to a modem) costs more than DSL or cable modems. While thisequipment and service continue to remain exorbitant, it is leaving the way openfor other Internet services to share the marketplace.

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    Frame RelayFrame Relay is a digital connection-oriented data service that sends packets ofdata, called frames, over the network. This frame of data is transmitted throughthe network and checked for errors. Frame Relay is designed for cost-efficientdata transmission for intermittent traffic between local area networks (LAN-to-LAN) and between end-points in a wide area network (WAN). It is a data networkservice bundled with leased line access for transmitting data between remotenetworks. Frame Relay is a digital packet network service that provides all thefeatures and benefits of a dedicated network service without the expense ofmultiple dedicated circuits. This data is carried in the form of packets and givenan ID on a per packet basis. It is then sent across the network in a very efficientway. In a Frame Relay network, circuits are connected to a packet switch withinthe network that ensures that packets are routed to the correct location. FrameRelay is a digital dedicated service that is leased from a carrier. It is a switchedservice.

    Application-level security Web applications can be protected from SQL Injection Attacks where

    the attacker enters SQL commands into Web form input fields or URLquery strings to try to manipulate the SQL statement being sent to andfrom the database. To avoid SQL injection attacks, the following methodsshould be used:

    o Use of queries or stored procedures to access a database as opposedto using string concatenation

    o Limitation the amount of characters in Web form input fields andURL query strings to a proper amount

    o Validate text input and URL query strings for improper characters(e.g. apostrophe, dash)

    o Do not display errors to the user that contain information about thedatabase or actual source code

    ASP.Net Web applications must be secured from Cross Site Scripting(XSS) attacks. To accomplish this, developers must ascertain that theASP.Net validateRequest Page directive is set to True (the default setting)so that users of the application are prevented from entering HTML orJavaScript code into Web forms.

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    Data transmission securityWhen confidential or important data is passed between the user and the Webserver, the HTTPS (SSL over HTTP) protocol will be used. SSL provides serverauthentication, data encryption (over the wire), and data transmission integrity.The SSL certificate used on the Web server will need to be trusted by the Webbrowsers listed on the CDEs Minimum Web Browser Requirement Web page.Database security

    Web applications should use minimum privileges to access databaseobjects (i.e. tables, views, stored procedures). For instance, if the Webapplication needs read-only access to a specific database table, thedatabase permissions should be set accordingly than giving the Webapplication admin or owner rights to the entire database.

    Individual database fields storing confidential or sensitive data (forexample, passwords, social security number) must be stored usingencryption techniques.

    Password requirementsPasswords whether created by application developers, administrators, or usersmust meet or be required through validation to meet all of the followingparametres. Passwords must:

    Be at least eight characters in length. Contain characters from three of the following four categories:

    o Uppercase letters (A though Z)o Lowercase letters (a through z)o Numbers (0 through 9)o Special characters (!, @, #, $, ^, &, *, -, =, _, +, ?)

    Not be the same as the logon or user name.

    Activity 2Select any two major broadband service providers in India and presenttheir pros and cons.

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    Self-Assessment Questions

    6. Fill in the blanks with appropriate words.(a) _________ refers to telecommunication where a wide band of

    frequencies is available to transmit information.(b) __________ is a digital connection-oriented data service that sends

    packets of data, called frames, over the network.(c) Passwords must be at least _____ characters in length.

    3.7 Summary

    Let us recapitulate the important concepts discussed in this unit: Common Gateway Interface (CGI) is a process used to share the data

    between the web server and the web browser. CGI is a set of standardswhere a program can send data back to the web server where it can beprocessed.

    CGI is the part of the Web server that can communicate with other differentprograms running on the server. With CGI, the Web server can call up aprogram, while passing user-specific data to the program (such as whathost the user is connecting from, or input the user has supplied usingHTML form syntax).

    The primary function of NIC is to allow the computer to communicate onthe network. It supports transmitting, receiving and controlling traffic withother computer on the network. NIC operates at physical layer of OSImodel.

    Network cables are the medium through which information generally travelsfrom one node/network device to another. There are many types of cableswhich are used for computer network. In some cases, a network will utilizeonly one type of cable, while other networks will use a variety of cabletypes.

    Fibre optic cabling consists of a centre glass core surrounded by severallayers of protective materials. It transmits light rather than electronic signalseliminating the problem of electrical interference. This makes it ideal forcertain environments that contain a large amount of electrical interference.It is also the standard for connecting networks between buildings, due toits immunity to the effects of moisture and lighting.

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    Wireless LANs use high frequency radio signals, infrared light beams, orlasers to communicate between the workstations, servers, or hubs. Eachworkstation and file server on a wireless network has some sort oftransceiver/antenna to send and receive the data. Information is relayedbetween transceivers as if they were physically connected.

    In general, broadband refers to telecommunication where a wide band offrequencies is available to transmit information. There is wide range offrequencies available, and information can be multiplexed and sent onmany different frequencies or channels within the band simultaneously.This way, more information can be transmitted in a shorter duration oftime than what is achievable with older methods of transmission.

    Integrated Service Digital Network (ISDN), is the original high-speedInternet service. It sparked the high-speed Internet development betweenservice providers during the 1990s and, of course, revolutionized Internetuse.

    3.8 Glossary

    Common Gateway Interface (CGI): Process used to share the databetween the web server and the web browser

    Hubs: Central locations in networks that bring media segments together Repeaters: devices that operate at the physical layer of the OSI model,

    whose basic purpose is to extend the distance of LAN Bridge: Device that is attached to two or more LANs to create an extended

    LAN Router: Operates at the third network layer of ISO-OSI model and

    connects more than two different types of network Network cables: Medium through which information generally travels

    from one node/network device to another Fibre optic cable: Cable that consists of a centre glass core surrounded

    by several layers of protective materials, and which transmits light ratherthan electronic signals

    Wireless LANs: LANs that use high frequency radio signals, infraredlight beams, or lasers to communicate between the workstations, servers,or hubs

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    Sikkim Manipal University Page No. 57

    Line-of-sight communication: Communication through unblocked directline between the workstation and the transceiver

    3.9 Terminal Questions

    1. What is CGI? 2. Discuss the main features of CGI.

    3. What are multimedia objects? Explain their use.4. Write a note on any five network access equipment.5. Discuss the use of network cables.6. Describe the various types of broadband telecommunication available.

    3.10 Answers

    Answers to Self-Assessment Questions

    1. (a) True; (b) False2. (a) Content; (b) Object-oriented, Data-driven3. (a) False; (b) False4. (a) False; (b) True5. (a) Glass; (b) RJ-456. (a) Broadband; (b) Frame Relay; (c) Eight

    Answers to Terminal Questions

    1. Refer to Section 3.22. Refer to Section 3.23. Refer to Section 3.34. Refer to Section 3.45. Refer to Section 3.56. Refer to Section 3.6

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    Sikkim Manipal University Page No. 58

    References

    1. Laudon, Kenneth C. and Carol Guercio Traver. 2004. E-Commerce:Business, Technology, Society. N.J: Prentice Hall.

    2. Turban, Efraim, Jae Kuy Lee and Michael Chung. 1999. ElectronicCommerce: A Managerial Perspective. Prentice Hall.

    3. Whitley, David. 1998. E-commerce: Strategy, Technologies andApplications. Tata McGraw-Hill.