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LESSON 1:INTRODUCTION TO EVENTS

Lesson objectives• Communication• Overview of networking• Advantages of networking• Disadvantages of network Network types• Accesing the network

OverviewTo understand the full potential of computers we need toexamine the computer network. A computer network consistsof two or more computers and/or other peripheral devices,called resources, linked together to form a communicationsystem that allows users to share information and resources. Incontrast, a stand-alone computer stores all data on its own diskdrives and is physically connected to each of its peripheraldevices. A network is a number of computers connectedtogether to share information and hardware. It facilitatescommunication among devices

Communicationis the systemic process of exchanging information betweenparties, usually via a common system of symbols.“Communications” is the academic discipline which studiescommunication.The Latin root word of “communication” is comunicare,which has three possible meanings1. “to make common”, which is probably derived from either2or32. cum + munus, i.e. having gifts to share in a mutual donation.3. cum + munire, i.e. building together a defense, like the walls of a

city

To be more accurate, a network is actually a system which canconsist of many things, including:1.thecomputers and peripherals2special networking cards inside each computer and peripheral3. the cables and communications lines which link all the computersand peripherals together4. central hardware devices which connect computers and route

data to the right places on the network (hubs, patchpanels,routers).

5. network opreting system software

6. networking software in each computer and peripheral that letsthem “talk” to each other7. an “address” system to identify each part of the network to all

the other parts8. often, a main computer or computers usually called servers or

hostsIt is a system that transmits any combination of voice, videoand/or data between users. The network includes the networkoperating system in the client and server machines, the cablesconnecting them and all supporting hardware in between such asbridges, routers and switchesThe primary advantage of using a network is thatresources, applications, and data can be shared. The following three examples illustrate these advantages. Thefirst example relates to sharing resources. In a school computerlab with thirty stand-alone computers you would need topurchase thirty printers if you wanted each student to printfrom his/her computer. In contrast, if you had thirty networkedcomputers (called workstations) each of them could print overthe network to a single printer.The second example concerns the storage of applications. Asstand-alone machines, each computer would need every programinstalled on the local hard drive (the C: drive). If you wanted tochange the settings or add another application you would need tocarefully repeat the process for each computer and hopefully thelocal hard disks would be large enough. On a network, settingsneed to be changed only once to impact all workstations, andprograms need to be installed only once on a network drive foreveryone’s access.A final example involves the storage of data. In a stand-aloneenvironment students must sit at the same computer to accessfiles stored on their hard drive. If a student comes in duringlunch to work on a report, for example, and someone is alreadyworking at that specific computer, the student cannot access thereport file. In a networked lab students can sit at any workstationand retrieve files from a network drive.Networked computers have many other advantages. Electronicmessages (called e-mail) can be instantly sent over a network.Communication can be improved with information broadcast toall appropriate people with less effort than a phone call ortypewritten memo. Electronic purchases can be made withoutstepping into a mall or using a car. And finally, students can accessencyclopedias and library resources across the globe without everleaving their bedroom. As networks have become a commonthread opening communication between millions of peoplethroughout the world, it is important to understand more abouthow networks function.

Network BasicsWe know the purpose of a network is to connect to anothercomputer to communicate and share resources. Every computer

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on a network needs to have a communication interface thatprovides that connection. Examples of these interfaces are thenetwork card that is plugged inside the computer, or a serialport. Workstations can be physically connected through asystem of cables, phone lines, or data lines. A wirelessconnection of infrared light, microwave, or satellite can also beused.A workstation on a network may also be referred to as a host.These hosts are connected to various specialized computers thatperform specific functions or resource sharing. These specializedcomputers are called servers. A file server refers to the specialcomputer on a network that is used to serve the workstations withtheir applications and data. A print server is used to manage theprinting jobs over the network and send them to the appropriateprinter. A CD-ROM server has many CD-ROMs that it makesavailable to the hosts. Organizations might employ applicationservers that only store and manage specific programs of theorganization such as a large database of information. Other serversinclude remote communication servers, mail servers, web servers,and domain name servers (more on these terms later).Sharing of resources such as printers is an important use of anetwork. Other resources that can be shared over a network includemodems, CD-ROMs, and tape back-ups.

Network Types

Operating SystemJust as a stand-alone computer needs an operating system tocontrol its processing, a network needs an operating systemtoo. There are two types of network operating systems: peer topeer and client-server .A peer is a person of equal standing. For example, a student’s peerwould be another student, while a teacher’s peer would be anotherteacher. In a peer to peer network all workstations have equalfunctionality and all their resources can be shared by any otherworkstation on the network. For example, each workstations’hard disk or CD-ROM drive may be considered a resource that allthe other workstations could access. No single computer managesor controls the peer to peer network; all workstations are equal.Examples of peer to peer network operating systems are Windowsfor Workgroups, Windows95, and Artisoft Lantastic.On a client-server network that relationship between computersis not of equality, but of customer and owner. The client(customer) is the workstation that connects to a server (owner),which in turn provides services. In a client-server network theservers are not usually used as a workstation because they arededicated to the task they perform (serving CD-ROMs, files,applications, etc.). Examples of client-server network operatingsystems are Novell Netware, Banyan Vines, WindowsNT Server, andOS/2 Warp Server.

LocationAnother way to define a network deals with location. Beginningwith the most concise network is the local area networkknown as a LAN. A LAN connects computers and otherresources in a workgroup, department, or building. Anetworked computer lab is an example ofa LAN. Next is aninternetwork. An internetwork is a collection of LANs withina building, group of buildings, or campus area. A computer lab

that is also connected to a library network would be an exampleof an internetwork. Finally, a wide area network, or WAN, isan internetwork that spans geographically remote areas. Becauseof its distance a WAN requires public or privatecommunication links such as phone lines or dedicated lines(such as ISDN) to interconnect each area. An example of aWAN is a connection between two campuses that are milesaway from each other.

Accessing the Network

Logging InPeople using networked computers are called users. Whenmany users have access to data and applications over a networkthere needs to be a system to protect sensitive information andensure that users are given access to resources they need. It isthe Network Manager ’s responsibility to handle these tasks.For example, a Network Manager would add a new user to thesystem and determine to which resources, applications, anddata the user can access (called assigning rights).Networks employ several methods and levels of security in orderto protect the integrity and privacy of all stored information.Assigning rights is one method that restricts users to specificpredetermined data and resources of the network. A secondmethod of securing the network is achieved through the processof gaining access to the network that is called logging in. Althoughthe process of logging in may vary slightly, in general there arethree steps. The information below refers to Novel Netware. Thethree steps of logging in can be compared to what you do whenyou go to a friend’s house.

STEP ONE: Knock on your friend’s door.The file server needs to know that you would like access to it.In order to “knock on the file server’s door” you need to usethe command LOGIN. When you type the word LOGIN andpress ENTER you are telling the computer to begin theprocess of giving you access to its resources. In some operatingsystems such as Windows95 a dialog box appears to help youthrough this log in process.

STEP TWO: Answer the question “Who is it?”Once you have the file server’s attention with the commandLOGIN, it asks you the question “Who are you?” Since itcannot orally ask you this, it displays the phrase Enter your loginname on the bottom of the monitor. Every network user has aunique user name that is also called the login name. Thelogin name is assigned by the Network Manager.

STEP THREE: Verify that you are who you say youareIf you were knocking at your friend’s door he/she mightrecognize your voice or peer through the peep hole to confirmthat you are in fact who you say you are. Since the file servercannot do this, it uses a secret password to confirm who youare. Your unique password is assigned by the NetworkManager and it should be changed frequently. When you typein this password you will notice that as you type nothingappears on the monitor. This is the way the file server keepsyour password secret-it does not display anything on themonitor as you type. If you make a mistake, press theBACKSPACE key until you hear the beeping sound.

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TOtherwise, just press ENTER once finished typing. If you havelogged in correctly, the system will present you with your mainmenu or application as defined by your login name.

RightsUsing the example of visiting a friend described above,depending on how good of a friend you are, you may not beallowed to enter all rooms in the house. The same is true withthe file server. Your rights to files, programs, and resources onthe file server are determined by your login name. For example,students who log in to a networked computer lab should nothave access to teacher’s tests and grades. Students might havethe right to create files in certain folders, but they may berestricted from deleting files or modifying certain ones. A usermight not be able to print on certain networked printers, accessa certain network drive, or start a particular application program.These rights associated with the login name and passwordmake it critical that younot share your password with anyone ifyou want your data to be secure. But remember, just as it iswrong to knock on a door and say you are a person other thanyourself, using someone else’s login name and password arealso wrong and can result in severe consequences.

Logging OutWhen you are ready to leave your friend’s home you wouldalways say good-bye and close the door after yourself. Youwould never think of just walking away and leaving the dooropen, would you? The same is true with the network. Until youofficially say good-bye, a procedure called logging out, you areleaving the door wide for an intruder to steal or modify yourfiles.To logout, close all programs and enter the command LOGOUT.In Windows95 the Shut Down dialog box gives you the option to“Close all programs and log on as a different user.” Once you logout the workstation is no longer linked to the file server usingyour login name and password. Again, remember that if yourealize someone forgot to logout, that does not give you licenseto access that user’s files. Just as we do not walk into a home ifsomeone accidentally left the door open, we do not use someoneelse’s rights because he or she forgot to logout.

Advantages of Networks :

• ·peripherals (eg printers) can be shared• software can be shared• data can be shared• computers may communicate• security - user access may be restricted if needed

Disadvantages of Networks :

• one server breaking down may affect a number of computers• vulnerable to hackers and viruses• cabling and installation may be expensive• a network manager may need to be employed to run the network

Points to Ponder

• A computer network consists of two or more computersand/or other peripheral devices, called resources, linked

together to form a communication system that allows users toshare information and resources

• Communication is the systemic process of exchanginginformation between parties, usually via a common system ofsymbols

• We know the purpose of a network is to connect to anothercomputer to communicate and share resources

• The person who takes care of the network is called a NetworkAdministrator

• A LAN connects computers and other resources in a workgroup,department, or building.

• WAN, is an internetwork that spans geographically remoteareas. Because of its distance a WAN requires public or privatecommunication links such as phone lines or dedicated lines

• When many users have access to data and applications over anetwork there needs to be a system to protect sensitiveinformation and ensure that users are given access to resourcesthey need. It is the Network Manager ’s responsibility to handlethese tasks.

• An internetwork is a collection of LANs within a building,group of buildings, or campus area

Students Activity

1. define computer networks?Why is it necessary?2. How communication is facilitated with networks?3. Define the role of network manager?4. Define various advantages & disadvantages of networks?5. How you can distinguish various types of networks?

Students Activity

1. define computer networks?Why is it necessary?

2. How communication is facilitated with networks?

3. Define the role of network manager?

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4. Define various advantages & disadvantages of networks?

5. How you can distinguish various types of networks?

STUDENTS ACTIVITY