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Syllabus outcomes5.2.1 Describes and applies problem-solving processes when

creating solutions.

5.2.2 Designs, produces and evaluates appropriate solutions to arange of challenging problems.

5.2.3 Critically analyses decision-making processes in a range ofinformation and software solutions.

OverviewThis chapter provides an overview of networking systems. Itexamines the nature of a communication network and datatransmission. You will learn network basics and the differentnetwork topologies. The chapter concludes by describing networkoperating systems.

NetworkingsystemsNetworkingsystems

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288 HI Tech: In format ion and Software Techno logy

13. 1 A communicationsnetworkA network is a number of computers and their peripheral devicesconnected together in some way. The simplest form of network iswhen one computer is linked to another computer. The Internet isa connected set of networks that links millions of computers.Computers communicate with each other through a network. Therole of a network is to transfer data from one location to another.Data stored on one computer can be obtained by people usingother computers, often thousands of kilometres away. The power ofone computer is not restricted to one room, but can be madeavailable anywhere.

Networks have changed the way we live and work. In mostworkplaces they are a necessity. There are a number of advantagesin establishing a network:• Sharing peripheral devices: Networks enable users to share

peripheral devices such as printers, hard disks and Internetaccess. It is common to find a small number of high-qualitynetwork printers shared by a large group of users on a network.Sharing peripheral devices reduces costs and allows morepeople to access the equipment.

• Sharing applications: Networks enable users to share applications.Networks that share applications usually require a site licence ora network licence. These licences allow the software to be usedon the same site or for a certain number of users. Networklicences cost less than purchasing multiple copies of the software.It also takes less time to install or update the network software.

• Sharing data: Networks provide a very fast method for sharingand transferring files. Many networks have a file server to storedata. Data stored on a file server can be accessed from anycomputer on the network. Users can instantly send a file toanother user on a network. Users can also access their files fromdifferent locations. Sharing data increases efficiency andproductivity (see Figure 13.1).

• Security of information: Networks secure files by restrictingaccess to authorised users. The entire network is backed up on aregular basis. It is not dependent on users backing up their files.Firewalls are used to protect data on the network from hackers.

• Improved communication: Networks enable users to worktogether in ways that otherwise would not be possible. Emailand messaging systems make it easy to communicate and share

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28913 Network ing systems

ideas. There is also a range ofsoftware designed for groupsof users on a network. Oneexample of this software isproject managementsoftware. It is a tool toefficiently plan, manage andcommunicate informationabout a large project.

On the other hand, establishing anetwork has some disadvantages:• Expensive to install: The

initial costs of networkinstallation is very costly. Servers, network devices, cables andnetwork software are expensive. A technician is usually requiredfor installation and this adds to the cost. However, generallyover time a network will save money.

• Administrative time: Maintenance of a network requiresconsiderable time and expertise. A person called a networkadministrator needs to be employed to manage the network.This is an added expense.

• Server failure: When the server ‘goes down’ the entire networkdoes not operate. Users do not have access to files andapplications. Loss of productivity can be significant.

• Damaged equipment: In some networks a broken cable can stopthe entire network. A faulty network interface card will preventusers of that computer accessing the network.

• Maintaining security: Networks are targets for hackers andviruses. The files stored on a network can be accessed, stolenand edited more easily than files stored on an individualcomputer. A virus that enters the network can spread to everycomputer on the network. Appropriate procedures need to beimplemented to maintain security.

ProtocolsA protocol (pronounced ‘PROH-tuh-cahl’) is a set of rules thatgoverns the transfer of data between computers. A protocol defineshow a link is established, how data is transmitted and how errorsare detected and corrected. When the same protocols are used,different types of computers and devices can communicate witheach other. There are numerous protocols that have been developedfor specific technology (see Figure 13.2) including:

Figure 13.1 Accessing data from a network



• TCP/IP (Transmission ControlProtocol/Internet Protocol) is astandard for data transmission anderror detection across the Internet.The TCP standards inform thereceiving computer what is inside thedata packet and the IP standard tellsthe computer where and how to sendthe data packet.

• IPX/SPX (Internetwork PacketExchange/ Sequenced PacketExchange) is a standard used for datatransmission in local area networks(LAN) that use the Novell NetWareoperating system.

• NetBEUI (NetBios Extended UserInterface, pronounced ‘net-booey’) isa standard used for data transmissionin local area networks that useWindows NT and LAN manager.

• AppleTalk is a set of local area network standards for AppleMacintosh computers. It is built into all Apple computers andApple laser printers.

Figure 13.2 Network protocols



Exercise 13.11 Copy and complete the following sentences:

a Networks enable users to share _______ devices.b Files and applications on a network are _______ to authorised

users.c _______ of a network requires considerable time and expertise.d TCP/IP is a standard for data transmission and error detection

across the _______.2 True or false?

a The Internet is a connected set of networks.b Sharing data on a network is a major disadvantage.c Networks are inexpensive to install.d Networks are targets for hackers and viruses.

3 What am I?a A number of computers and their peripheral devices connected

in some way.b A set of rules that governs the transfer of data between

computers.c A standard used for data transmission in the local area

networks that use Novell NetWare.4 a What is the role of a network?

b List five advantages in establishing a network.c How do networks improve communication?d What are the consequences if the server of a network goes

down?e Why is a virus a concern on a network?f List four protocols commonly used on a network.

Development5 A business is planning to establish

a local area network to improveefficiency and productivity.What would be some of thebenefits of networking?Installing a network isexpensive. What costs areinvolved in establishing anetwork?

6 Network protocols areoften developed inconjunction withimprovements in technology.Do research into two protocolsthat are commonly used on anetwork. Prepare a report thatsummarises your investigation.



13. 2 Data transmissionData transmission on a network involves serial transmission. Ittransfers data by sending one bit at a time through a single line.All data on a network is transferred using a data transmissionmode, a data transmission rate and a data transmission medium.

Data transmission modesThe data transmission mode describes the direction of data flow.It is either simplex, half duplex or full duplex (see Figure 13.3).• Simplex mode allows transmission in one direction only, from

the sender to the receiver. An example of simplex mode is theradio, television or a school broadcast system. Remote sensorssend information to a computer using simplex mode.

• Half duplex mode allows transmission in both directions but notat the same time. This means the sender and the receiver taketurns. An example of half duplex mode is an intercom orwalkie-talkie. Disk drives and printers transfer informationusing half duplex mode.

• Full duplex mode allows transmission in both directions at thesame time. Most communications systems use full duplexmode, such as the telephone or email. A computer uses fullduplex for most of its communication.

Data transmission ratesData transmission rate is the speed of data transfer. It is measuredby the number of bits per second or its baud rate.• Bits per second (bps)—the number of bits transmitted in one

second. Common units of measurement for transmission speedare kilobits (Kbps), megabits (Mbps), gigabits (Gbps) or terabits(Tbps) per second. Bits per second is also called the bit rate.

Simplex modeHalf duplex mode

Full duplex mode

one way

one at a timeboth ways

both wayssimultaneous

Figure 13.3 Transmission mode



• Baud rate—the maximum number of electrical signalstransmitted in one second. It is different to bits per second as anelectrical signal can contain more than one bit of data. Forexample, a 2400 baud might transmit at 4800 bps. Here oneelectrical signal is roughly equal to two bits.

The speed of data transmission is determined by the device and the bandwidth. The bandwidth is the quantity of information thatcan be sent through a transmission medium. The transmissionmedium is the pathway for transferring data between the devices.A transmission medium with a high bandwidth can transfer moredata in the same amount of time. The transmission medium iseither a wire transmission or a wireless transmission.

Data transmission—wireWire transmission transfers the data through wires and cables. Thesecables must be protected from damage, they take up space and canbe difficult to install. However, wire transmission can carry largeamounts of data with little interference from other signals. Wiretransmission includes twisted-pair cable, coaxial cable or opticalfibre cable (see Figure 13.4).• Twisted-pair cable consists of pairs of insulated copper wires,

twisted to form a spiral. Twisting reduces the amount ofinterference from other cabling. Unshielded twisted-pair (UTP)is used on a network. There are two common standards forUTP called 10Base-T (10 Mbps Ethernet) and 100Base-T (100Mbps Fast Ethernet). UTP is preferred as it is cheap and easy toinstall. It is suitable for a maximum distance of 100 metres.

• Coaxial cable (coax, pronounced ‘co-axe’) has a single copperwire surrounded by an insulator, grounded shielding and anouter insulator. The shielding allows data to be transmitted with

Baud rate wasnamed after theFrench inventor J. M. Emile Baudot(1845–1903). It wasused to measurethe speed ofMorse codetransmission.

Twisted-pair

Conductor

Insulator

Coaxial cable

Outer insulation

Grounded shielding

Insulation

Inner conductor

Optical fibre cable

Covering

Cladding

Glass optical fibre

Figure 13.4 Wire transmission

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little distortion. It is more dependable than UTP, however, it ismore expensive and less flexible. The most common standardfor coaxial cabling is 10Base2 (10 Mbps Ethernet). It is suitablefor a maximum distance of 200 metres.

• Optical fibre cable is a very thin fibre of clear glass or plastic thatcarries light waves. Optical fibre cable is becoming the standardfor wire transmission. Optical fibre cables are free fromelectromagnetic and radio interference, very secure, light andtransmit data at high speeds without errors. Optical fibre cablescan, in theory, transmit data in excess of 10 Tbps. However, theyare more expensive than other types of wire transmission.Optical fibre is suitable for long distances.

Data transmission—wirelessWireless transmission moves the data through air and space. It doesnot need a fixed physical connection between the source and thedestination. Wireless networks allow devices to communicate usingradio waves, microwave and satellite:• Radio waves are used to transfer data by connecting a small

radio transmitter to each device (see Figure 13.5). Thetransmitter sends and receives data through the air using radiowaves. The most common wireless networking standards are802.11b (11 Mbps) and 802.11g (54 Mbps). The major problemwith radio waves is their lack of security. The signals can beintercepted by anyone.

• Microwave is a high frequency radio signal sent through spacein a straight line from one antenna to another. It has been used

for several decades to transmitboth voice and data. Antennaeare placed on tall buildings ormountain tops to continuetransmission over longdistances. Even though it isreasonably error free, weatherconditions or objects such astrees and buildings willobstruct the signal and affectthe transmission. Microwavetransmission is commonlyused with satellites for longdistance transmission.Figure 13.5 Wireless PC Card



• Satellites are specialised receivers and transmitters that arelaunched by rocket and placed in orbit around the earth.A signal is sent from one ground station to the satellite, whichreceives and re-transmits the signal to another ground station.Each ground station uses a satellite dish to send and receive thesignals. Satellites can transmit large amounts of data over longdistances and at great speeds. There are hundreds of satellitescurrently in operation. They are used for weather forecasting,television broadcasts, radio communications and Internetcommunications.

Wireless networks have become popular for small networks inhomes and small businesses. The main reason for their popularityis that they do not require cables. Installing cabling requires aspecialist. In addition, there could be problems obtaining accessunder the floor or over the ceilings in some buildings. Wirelessnetworks are installed without digging or drilling. However,wireless transmission transfers data at slower speeds and hasproblems in maintaining signal quality compared to wiretransmission.

Exercise 13.21 Explain the difference between:

a simplex mode and half duplex modeb bits per second and baud ratec twisted-pair cable and coaxial cable.

2 What am I?a Transmission mode that allows transmission in both directions

at the same time.b A very thin fibre of clear glass or plastic that uses light waves.c Transmission media that moves data through air and space.d A high frequency radio signal sent through space in a straight

line from one antenna to another.3 Copy and complete the following by replacing the letter in brackets

with a suitable term:Wire transmission transfers data through wires and (a). It can carrylarge amounts of data with little (b) from other signals. Wiretransmission includes (c) cable, coaxial cable and (d) cable.

4 a List four common units of measurements for transmission speed.b What is the bandwidth?c What are the reasons for choosing UTP for wire transmission?d What are the advantages of optical fibre cables?e What are the major problems with radio waves?f Why have wireless networks become popular?

Interactive



Development5 Investigate the latest standards for wire transmission. Construct a

table that compares each standard in terms of cost, distance andspeed. Which standard of wire transmission would you prefer? Givereasons for your answer.

6 Eddie has three computers at home. He would like these computersto share files, applications and peripherals. Eddie is not sure whichdata transmission medium would be most appropriate. What advicewould you give Eddie? Give reasons to explain your answer.

13. 3 Network basicsA network is a number of computers and their peripheral devicesconnected together in some way. Each device on a network is calleda node. There are networks of all shapes and sizes using wire orwireless transmission.

Types of networksNetworks are classified as local area networks, wide area networksor as virtual private networks.• A local area network (LAN) is a network on one site, such as

within a building or group of buildings. A LAN is often acollection of computers and peripheral devices. LANs enableusers to share resources and communicate with each other moreeffectively. These tasks are completed using a network operatingsystem (NOS). The physical arrangement of the devices on aLAN is called the network topology. There are many possiblenetwork topologies, such as star, bus and ring.

• A wide area network (WAN) is a network that covers a very largearea. It is often made up of a collection of LANs (see Figure 13.6).A WAN may use a private leased line, the normal telephonenetwork or a combination of both. A private leased line isdedicated to the network. It offers higher transmission speeds andmore accurate transfer of data than those available through thePublic Switched Telephone Network (PSTN). PSTN links arerelatively cheap if computers do not require constant connection.However, the link is not guaranteed and can be interrupted.

• A virtual private network (VPN) is a private network carryingencrypted data across the Internet. It uses the PSTN and theInternet to create an organisation’s network. A VPN aims toprovide an organisation with the same capabilities as a LAN butat a much lower cost. It uses encryption and other security



measures to ensure onlyauthorised users haveaccess to the VPN.Encryption is the processof coding data anddecryption the process ofchanging it back. Data iscoded, transmitted andthen converted back to itsoriginal form. Encryptionis used to prevent datafrom being interceptedduring transmission andto maintain the privacy of the VPN.

Components of networksThere are a range of components for networks such as servers,workstations, hubs, switches, routers, bridges, gateways, repeatersand network interface cards.• A server is a computer that provides resources to other

computers on the network. The server provides access to files,applications or peripheral devices. There are different types ofservers, such as the following:— A file server is a controlling computer in a network that

stores the programs and data shared by users. The filesstored on this server can be retrieved by authorised users.

— A print server is a computer in a network that controls oneor more printers. Print servers have printers attached tothem and are accessed by authorised users. If the printer isbusy the data to be printed is stored in the print server andplaced at the end of a queue. A print server can be used withor without a file server.

— A mail server is a computer in a network that provides emailfacilities. It stores incoming mail for distribution to usersand forwards outgoing mail to appropriate devices. Somemail servers can be accessed from the Internet.

— A web server is a computer in a network that stores anddistributes web pages. When a network user accesses a webpage from the Internet it is stored in the web server.Websites are downloaded and stored on web servers. Whenyou browse the Internet you are travelling from one webserver to another.

Satellite

Local areanetwork (LAN)

Local areanetwork (LAN)

Figure 13.6 WANs are often made up of LANs



• A workstation is a personal computer on a network. It hasmemory, storage and processing capabilities. Workstations canoperate independently of the network. They access a server forfiles and applications but process the data themselves.

• A hub is a central connecting device in a network. Each node isconnected directly to the hub. Most hubs were initially dumb.They receive a data packet from one node and send that datapacket to all nodes on the network. This created a lot ofunnecessary network traffic, as most of the nodes will ignorethe data because it is not addressed to them. A better type ofhub is called a switch.

• A switch is an intelligent hub that only sends data to a specificnode (see Figure 13.7). The switch looks at the address of thedata packet and sends it to that address. A switch reduces thevolume of traffic on a network compared to a hub.

• A router is a very intelligent hub thatdirects (routes) data packets to and fromother networks. It makes its decision onits current understanding of thenetworks. A router maintains a table ofthe available routes and their conditions.It uses this table to determine the bestroute for a given data packet. Routersare often used to connect to the Internet.

• A bridge is a device to link two similar networks. It oftenconnects networks that use the same protocol such as Ethernet.A bridge examines each data packet on a network and forwardsany data packets addressed to a connected network.

• A gateway is a link between two different types of networks. Itconverts different protocols and transfers data between the twonetworks. For example, a gateway could be used to convert aTCP/IP packet to an IPX packet. A gateway acts as the doorbetween the networks. All the data must pass through thegateway to reach the other network. Gateways are notnecessarily separate devices but rather are often pieces ofsoftware running on servers or in routers.

• A repeater is used to rebuild a fading signal to its originalstrength and shape before transmitting it onwards. For example,the data sent along a UTP cable becomes unreadable after about100 metres. A repeater would be installed every 100 metres torebuild the signal. A repeater ensures that the data is received asit was sent.

Figure 13.7 Switch

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• A network interface card(NIC, pronounced ‘nick’) is an expansion card thatallows a device to beconnected to a network (see Figure 13.8). NICs areinstalled into servers,workstations and some otherdevices. Each device musthave a driver tocommunicate on thenetwork. A NIC is usuallygiven a unique address sothat it can be identified on the network. Most NICs require anetwork cable connection and have connectors on the card fordifferent types of cables.

Client–server and peer-to-peer networksA client–server network is a network that uses one or more computersas servers and all the remaining computers as clients. Each server is apowerful computer that contains resources to be shared with clients.Most organisations use the client–server network for their LAN. Aclient–server network involves using a network operating system(NOS). A NOS allows the server to complete requests from clientsfor resources. The majority of the NOS is installed on the server buteach client has NOS client software. The NOS client software is usedto send requests to the server.

A peer-to-peer network is a network where there is no centralserver but each computer is both a server and a client. It is a simplenetwork that usually connects less than ten computers. A peer-to-peer network is used in homes and small offices to share files,peripheral devices and one Internet connection. In a peer-to-peernetwork each computer is considered a peer because it is equal andshares resources with others without a server. Each user determineswhich resources on their computer are to be shared. Operatingsystems such as Windows XP and Mac OS have the software tooperate a peer-to-peer network. A P2P is an Internet peer-to-peernetwork on which users connect directly to each other’s hard disksand exchange files over the Internet.

Figure 13.8 Network interface card



Exercise 13.31 What am I?

a A private network carrying encrypted data across the Internet.b A controlling computer in a network that stores the programs

and data shared by users.c A link between two different types of networks.d A network with no central server but each computer is both a

server and a client.2 Copy and complete the following sentences:

a A _______ is a network on one site such as within a building orgroup of buildings.

b A workstation is a _______ on a network.c A _______ is a very intelligent hub that directs data packets to

and from other networks.d A NIC is an _______ that allows a device to be connected to a

network.3 True or false?

a A WAN is often made up of a collection of LANs.b Each node is connected directly to a hub.c A bridge is used to rebuild a fading signal to its original

strength and shape before transmitting it onwards.d Most networks use a peer-to-peer network for their LAN.

4 a Describe a VPN.b List four different types of servers.c Why is a switch a better type of hub?d How does a gateway work?e Why is a NIC given a unique address?f Where are peer-to-peer networks used?

Development5 Investigate a LAN either at your

school or in the local community.Draw a plan that shows thearrangement of devices on thenetwork. Identify all componentsof the network. What types ofdata transmission media are usedon the network?

6 VPNs have been used by someorganisations to save money.However, there are risks inestablishing a VPN. Do research intoVPNs. Outline the advantages anddisadvantages of a VPN.

7 Hubs, switches and routers are used as central connecting devices.Do research to find more information on these devices. Write areport that summarises your investigation.



The word ‘bus’was used todescribe a bustopology as itperforms a similartask to a bus onthe road. The bustravels along aroad (bus cable)and picks up/dropsoff passengers(data) at bus stops(nodes).

13. 4 Network topologiesNetwork topology is the physical arrangement of the devices on aLAN. The type of network topology is not determined by the shapebut by how each node is connected to other nodes. There are manypossible network topologies (see Figure 13.9):• A star topology has a central node with each device connected

directly to it. The central node is usually a hub, switch or router.The central node receives messages and sends them to thedestination device. Star topology requires extra cabling as eachdevice needs a cable to the central node, not the nearest device.If one device or cable is broken the network can still operate.However, if the central node fails then the network fails.

• A bus topology is an arrangement where all the nodes areattached to a cable called the bus. Each device has a uniqueidentity and can only recognise those signals intended for it.Nodes check the bus, and retrieve their messages as data travelsalong the bus. Each node is considered to be connected to everyother node and can communicate directly along the network toany device. Bus topology is one of the easiest and cheapest to setup. It can still operate if one node fails and nodes are easilyadded. However, a faulty bus will stop the network and datacollisions can occur on the bus.

• A ring topology is an arrangement where all nodes are attachedin the shape of a closed loop. Each device in the ring has aunique address. Data flow is in one direction, moving fromnode to node until it arrives at its destination. Ring topology isdependent on the ring—if it is faulty the network will stop.

Ring topologyBus topology Star topology

Figure 13.9 Network topologies



Network access methodsThere are a number of ways of dealing with multiple users wantingto access the network at the same time. The two most commonaccess methods are discussed below:• Ethernet is the most common standard used in star or bus

topologies. It allows data to be transmitted in both directions atthe same time. Unfortunately this causes data collisions anderrors. To overcome this problem Ethernet uses a method calledCarrier Sense Multiple Access/Collision Detection (CSMA/CD).In CSMA/CD all nodes have the ability to sense signals on thenetwork. When a node wishes to transmit, it ‘listens’ for signals.When there is no signal it transmits. However, occasionally acollision will occur if two nodes listen for signals at the same.When a collision is detected the node stops transmitting and re-transmits at another time. The most common Ethernetstandards are Fast Ethernet (100 Mbps) and Gigabit Ethernet (1 Gbps).

• Token ring is the standard used on the ring topology. The tokenring operates by continually passing special data packets calledtokens between nodes. Workstations with data to send capture afree token and attach data along with addressing information. Abusy token with data cannot be used by other nodes. When thedata arrives at the destination, the data is replaced with anacknowledgement and sent back to the original sending node.

Security of informationA network aims to share resources and provide communication forusers. It provides an opportunity for hackers to access data.Network security requires careful planning and needs constantreview to ensure procedures are appropriate. Security ofinformation involves storage, backup and data security.

Networks are required to store huge quantities of data. Storageinvolves using magnetic disk and magnetic tape. Magnetic diskstorage is used when immediate access to data is required. It usesdirect access. This form of access allows data to be found directlywithout accessing all the previous data. Magnetic tape is used as abackup medium. It can store large quantities of data inexpensively.Magnetic tape uses sequential access. This form of access starts atthe beginning of the tape and reads all of the data until therequired item is found.

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Network users are encouraged to store important files on theserver. However, a server is exposed to many risks such as a crash,theft or circuitry failure. Regular backups of data stored on theserver are essential. A backup is another copy of the data that couldbe used to rebuild the system. Backups are sent to a warehousestorage facility through the Internet or secured offsite. If the systemgoes down the recovery process rebuilds the system. The success ofbackup and recovery depends on implementing appropriateprocedures.

Data security is a series of safeguards to protect data. There is arange of security techniques that apply to networks:• User identification is the ability to identify the user to the

network and to confirm their identity. A user is identified byentering a user ID and confirms their identity by entering avalid password. A password is secret words or numbers that aretyped on the keyboard to gain access to the system.

• Logon security involves protecting user ID and passwords fromunauthorised access. The password file should be encrypted andsecured.

• Access controls restrict users or a group of users to those filesand resources they need to perform their job (see Figure 13.10).When connecting to a network a certain level of access isgranted. This is done during a process of logging on.

• Data encryption is used to preventdata from being intercepted duringtransmission. Encryption is theprocess of coding data anddecryption the process of changing itback. It is the most effective way toachieve data security during thetransmission of data. Data is coded,transmitted, and then converted backto its original form.

• Firewalls are used on a network tocheck all incoming data for thepurpose of verification andauthentication. A firewall aims toprotect the network from hackerstrying to access sensitive information.Large networks have more than onefirewall because barriers need to beplaced at all critical points. Figure 13.10 Access controls for a network



• Anti-virus software is used to scan the network for a range ofwell-known viruses. Data infected by a virus is often costly torepair or impossible to replace. There is no guarantee that anti-virus programs will stop every virus, as new viruses are alwaysappearing. However, if the network uses the latest virusdefinition files and regularly uses the anti-virus programproblems will be minimised.

Exercise 13.41 Explain the difference between:

a a star topology and a ring topologyb Ethernet and token ring.

2 Copy and complete the following sentences:a Network topology is the physical _______ of devices on a LAN.b The central node in a _______ topology is usually a hub, switch

or router.c Logon security involves protecting _______ and passwords from

unauthorised access.d _______ is used to prevent data from being intercepted during

transmission.3 Copy and complete the following by replacing the letter in brackets

with a suitable term:Bus (a) is an arrangement where all the nodes are attached to acable called a (b). It can still operate if one (c) fails and nodes areeasily added. However, data (d) can occur on the bus.

4 a How do devices in a bus topology access data?b What is CSMA/CD?c Describe the storage devices used on a network.d Why is it essential to perform regular backups of data stored on

a server?e What is user identification?f When are access controls granted?

Development5 A LAN is to be constructed with eight nodes in a star topology. The

central node is a switch. Use graphics software to show thisarrangement. Illustrate how a star network transfers data.

6 A LAN is to be constructed with a file server, printer and fiveworkstations in a bus topology. Use graphics software to show thisarrangement. Illustrate how a bus network transfers data.ICT 13.1



13. 5 Network operatingsystemsA network operating system (NOS) is an operating system tosupport computers connected on a LAN. Some common examplesof network operating systems are Novell’s Netware, AppleShare andMicrosoft’s Windows XP Server (see Figure 13.11). Most of thenetwork operating system is installed on the server but each clienthas NOS client software. The NOS client software is used to sendrequests to the server. The NOS performs a range of different tasks.

Network operating system tasksNetwork operating systems control the flow of data between thedevices on the network and the requests for data. The networkoperating system organises messages from nodes until the networkis ready to process the message. The tasks performed by a networkoperating system and the administrator of the network include:• Administration—adds, removes and organises users. Groups of

users are often given the same permissions and rights.Permissions and rights allow access to particular files andresources.

• File management—gives users access to the remote hard diskson the server. It provides a file system and the ability to managea network directory. Drives and directories are mapped forusers.

• Applications—handles requests from users to share applications.The NOS is used to install software. It is easier for networkadministrators to comply with software copyright laws using anetwork. Access to the application files is restricted.

Figure 13.11 Novell Netware

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• Resource management—allows network devices such as printersand modems to be shared. It assigns users to printers and ordersprint jobs. The NOS is able to track the use of resources. Thisassists with budgeting.

• Security—monitors and restricts access to network resources. Itis often much easier to secure data on a network compared tosecuring data on a large number of computers. Anti-virussoftware is used to protect the network from viruses. Regularbackups are implemented for data stored on the network.

Most networks are connected to the Internet. A NOS must be ableto manage the flow of data between a LAN and the Internet.Security of the data on the network is an important issue. MostNOS provide a firewall to protect the network. Firewalls are used tocheck all incoming data for the purpose of verification andauthentication. A hacker who attempts to enter the networkthrough the Internet will be blocked by the firewall.

Logon and logoff proceduresWhen connecting to a network a certain level of access is granted.This is done during a process of logging on. Logon is the procedureused to get access to the network. The user is identified by means ofa user ID and a password. The user ID usually conforms to alimited length such as eight characters, and the password mustcontain at least one digit. The password is an important securitymeasure and must not be readily available or easily guessed byothers (such as using a nickname). The network must also keeppasswords secure. The password file should be protected fromunauthorised access and encrypted. Network systems may requireusers to frequently change their passwords as a security measure.

After logging on the user is given access toonly those features authorised by the networkadministrator. The logon procedure usuallyallows the user two or three attempts to enter

the correct name and password. Mistakescan occur in typing or in the datatransmission. The correct procedure of logging off should always be carriedout. This ensures all data is correctly

saved and programs are closed in thecorrect manner. Logging off also reduces

the risk of unauthorised persons accessingthe network.

Maintaining areliable backupand recovery planfor data on anetwork is thesingle mostimportant dailytask for a networkadministrator.



Project: Simple networkAngela Kocoski wanted to link two PCs together so that they couldshare files and peripherals. She required an easy and inexpensive wayto create this network. Angela solved the problem using the fourstages in project development.

• Define and analyse the problem: Angela discussed the project witha salesperson at the local computer store. She browsed the Internetto gather alternative solutions. Angela wrote a project plan.

• Design possible solutions: Angela decided to use a Fast Ethernetstarter kit. It contained all the equipment needed to create thenetwork for less that $200. Angela investigated three starter kitsand decided to purchased the Netgear Fast Ethernet starter kit.

• Produce the solution: The kit contained two NICs, a switch and twocables for connecting each NIC to the switch. Angela followed themanual to install the NICs into the motherboard of each computerand for connecting each cable. After completing the installationAngela started up her computers and transferred her first file.

• Evaluate the solution: Angela is pleased with her simple network.There have been no problems with the equipment and the speedof transmission is more than adequate.

Tasks1 Research the Internet to find current solutions for creating a simple

network. Describe these solutions.

2 Do you think a wireless network would be a better solution forAngela? Give reasons for your answer.

Figure 13.12 Netgear

ICT 13.2



Exercise 13.51 True or false?

a A NOS is an operating system to support computers connectedon a WAN.

b Most of the NOS is installed on the server.c File management is a NOS task that adds, removes and

organises users.d It is easier to secure data on a large number of computers than

data on a network.2 Copy and complete the following by replacing the letter in brackets

with a suitable term:A NOS must be able to manage the flow of data between a (a) andthe Internet. Most NOS provide a (b) to protect the network. A (c)who attempts to enter the network through the (d) will be blockedby the firewall.

3 Unjumble these words:a wfalirelb aoprdssw

4 a Describe the administrative tasks performed by the NOS andthe administrator of a network.

b Why do administrators find it easier to comply with softwarecopyright laws?

c How does the NOS manage resources?

d What is the purpose of anti-virus software?

e Describe the logon procedure.

f What is a password?



Development5 ‘A NOS provides a file system and the ability to map drives and

directories for users.’ Explain this statement. What are theadvantages of restricting access for users?

6 Efficient networks are dependent on the network administrator.Research newspapers and the Internet to find information aboutthe role of a network administrator and employmentopportunities. Write a brief report that summarises the result ofyour investigation.



Part A: Multiple choice questionsSelect the alternative (a), (b), (c) or (d)that best answers each question.

1 Which of the following is not anadvantage in establishing a network?a Administrative timeb Sharing datac Communicationd Sharing peripherals

2 What is the standard for datatransmission and error detection overthe Internet?a IPX/SPXb NetBEUIc TCP/IPd Internet protocol

3 Which of the following describesdata transmission in both directionsbut not at the same time?a Simplex modeb Half simplex modec Full duplex moded Half duplex mode

4 Which of the following is themaximum number of electricalsignals transmitted in one second?a Baud rateb Bits per secondc Signals per secondd Bit rate

5 Which of the following describes anetwork on one site such as within abuilding or group of buildings?a WANb VPNc NICd LAN

6 Which of the following is a bridge?a Expansion card that allows a

device to be connected to anetwork

b Device to link two similarnetworks

c Link between two different typesof networks

d Central connecting device on anetwork

7 Which of the following is anintelligent hub that only sends a datapacket to a specific device?a Repeaterb Gatewayc Routerd Switch

8 Which of the following is a networktopology that has a central nodewith each device connected directlyto it?a Ring topologyb Star topologyc Bus topologyd Central topology

9 Which of the following is a networkaccess method used in star or bustopologies?a Token ringb Logonc Encryptiond Ethernet

10 Which of the following is notperformed using the NOS?a Arrangement of nodes on a LANb Adding and removing usersc Installing softwared Mapping drives and directories

for users



Part B: Match the termFor each of the following statements (1 to 10), select from the list of terms (a to j)the one that most closely fits the statement.

Statements

1 A number of computers and theirperipheral devices connected in some way.

2 Set of rules that govern the transferof data between computers.

3 The number of bits transmitted inone second.

4 The maximum number of electricalsignals transmitted in one second.

5 A network that uses one or morecomputers as servers and all theremaining computers as clients.

6 A network where there is no centralserver but each computer is both aserver and a client.

7 A computer that provides resourcesto other computers on the network.

8 The physical arrangement of deviceson a LAN.

9 A network topology where all thenodes are attached in the shape of aclosed loop.

10 An operating system to supportcomputers connected on a LAN.

Termsa Baud rateb bpsc Client serverd Networke Network topology

f NOSg Peer-to-peerh Protocoli Ringj Server

Part C: Extended response questionsWrite at least one paragraph for each of the following:

1 Networks are a necessity in mostworkplaces. What are thedisadvantages in establishing anetwork?

2 There are three types of wiretransmission. Briefly describe eachtype of wire transmission.

3 Explain the difference between:a a local area network and a wide

area networkb a client–server network and a

peer-to-peer network.

4 Many LANs are linked together.Describe three components of anetwork that link LANs together.

5 Define the following types ofnetwork topologies. Briefly state theadvantages and disadvantages ofeach topology:a star topologyb bus topology.

6 What is a NOS? Outline the tasksperformed by a NOS and theadministrator of the network.

e Tester



Project: Avon High SchoolAvon High School is a new school whose first enrolment will be next year. Theschool expects a future enrolment of 1000 students with approximately seventystaff. The school needs a local area network to operate throughout the school.Staff and students require access to this network and the Internet. Design anetwork to solve this problem. Create a building plan for Avon High School. Thesolution requires details on the type of network, components of the network,network operating system, data transmission media, proposed location of theequipment and security. The network should be designed using the latest networkinfrastructure. Standards and costs need to be outlined. This is a group project tobe developed using the four stages in project development.

Project 6.1

Project 6.2

Project 6.3


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