Chapter 2

Introduction to Local Area Networks

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In this chapter we will be introducing Local Area Networks.  We will talk about why we use LAN's, some characteristics of a LAN's, as well as what needs to be considered when selecting a LAN.

Why Use LAN's

  • Resource Sharing - One of the main reasons LAN's were developed was to share resources.  It is a lot cheaper to have 10 computers shared one printer then it is to have each computer have it's own printer.  There are many ways to share a printer among users.

    • One method is having one computer hooked to a printer.  Whenever anyone else wants to print they would put their file on a floppy disk and carry it to the computer with the printer.  This is also called sneaker net.

    • Another method is a data switch box.  With this configuration you can have 2 to 4 computers and one printer hooked to a switch box.  You would then manually turn a switch to the computer that needs to print.  Newer switch boxes can automatically switch for you.

    • A third is too hook the printer to the network so other workstations can print to it.  There are many ways to configure this setup.  This is covered in more detail in Chapter 7.

  • Communication - In a telephone system communication usually consists of two people talking.  In a Network, communication can involve people talking via e-mail or an instant messaging program, it can also include communication between applications and between users and applications.

  • Management Control - You can control what the user sees and the applications that they use.  Also, backups and databases can be maintained from a centralized location.  This can prevent from having many departments maintaining a user database.  If two departments had different user databases and one department changed a users password, the password in the other database would not match.  If you had a network virus program you would be able to keep clients updated and scan for infected computers.  (More about viruses in Chapter 10)

  • Cost Effectiveness - When resources are shared money is saved.  Also since communication between employees increases so does productivity.  And when you move to a network their is a reduction of paper work which also saves the company money.

  • Downsizing- Moving from a large mainframe to smaller LAN can save money.  You would no longer need to pay high priced specialists to work on it, and the maintenance costs on a LAN are lower.

  • New Application Software - Workgroup applications allow for increased productivity and are a main reason for using a LAN.  Below is a list of common workgroup applications.

Application Software

In this section we will summarize the different types of applications used on a LAN.

  • Personal Productivity Applications - I have listed the associated Microsoft applications for each.

    • Personal Productivity Software
    • Word Processing and Desktop Publishing - Microsoft Word and Microsoft Publisher
    • Spreadsheets - Microsoft Excel
    • Database Management (DBMS = DataBase Management System) - Microsoft Access
    • Presentation Services - Microsoft PowerPoint
  • Workgroup Applications - These are networked applications
    • E-Mail - Not a lot needs to be said about e-mail.  This has become one of the primary means of communication worldwide.
    • Electronic Appointment Calendars - A networked calendar that will allow multiple people to view and update a single calendar.
    • Electronic File Cabinets - A location where files can be stored and retrieved by all.  Usually a shared location would have security setup to prevent accidentally deletion or viewing.  More on this in Chapter 10
    • File Exchange Utilities - A program that will let you exchange files with another user.  An FTP program would be an example.  Almost all e-mail program provide this function as well.
    • Project Management Systems - A network program that will allow you to keep track of the status of a project.  Usually supporting a time table, a task list with status updates, as well as other project tracking related tasks.  Multiple people would be able to view and update this information.
    • Group Decision Support Systems - "In a GDSS environment, there is usually a big room with something like 40 seats, which means that 40 people can be at the meeting at any one time. There are not only 40 seats but also 40 microcomputers. This enables every participant to have the use of one microcomputer during the course of the meeting. The reason why each participant needs a microcomputer depends on how GDSS works.

      In the GDSS, with special computer software, the facilitator of each meeting will first make the agenda of the meeting, which will be projected onto a big screen that everyone can see. Then the participants will type simultaneously in their ideas of the topic of discussion on the individual microcomputers next to them. Then the computer will sort the ideas, and then the participants will then vote or comment on which ideas they like or they dislike. In the course of the whole meeting, GDSS stores, categorizes and prints out all the ideas, comments and vote tallies, so that each of the meeting participants will get a summary of the meeting when it ends." - Source

    • Electronic Meeting System - A way to video conference with the addition of text, and graphics.  This can be cost effective if it uses an existing WAN connection.
    • Document Management Systems - Helps organize and control access to documents.

Characteristics of LAN's

  • Transparent Use - The user should not realize he/she is accessing data on a remote computer.  For example, if a computer has a network share mapped to a drive letter, when that user accesses the drive it should appear to the user as if the drive is local.

  • Mixed Hardware and Software -  You should be able to have different types of computers share information.  If the graphics department uses Macintosh's and the accountants use PC's they should be able to talk and exchange data.

  • Limited Geographical Area - A LAN is usually on one site.

  • High Speed - A LAN should be high speed.  Typically 10Mbps or higher.  Speeds can be 4, 10, 16, 100, 1000, 2000 Mbps.  1000 Mbps = 1 Gbps

  • Resource Sharing - Printers, Hard Drives, Data etc.... can be shared.

  • LAN Media - The type of media that is used on a LAN is large part of the network and is covered in Chapter 3.

  • Media Access Control Protocols - The method a node uses to gain access to the network is different on a LAN then it is on a WAN.  We will be discussing MAC protocols in Chapter 4.

  • Local Ownership - In a LAN the cable that connects the nodes together is owned by the company.  You do not have to rent the cable from anyone.

LAN Selection Criteria

  • Cost - Is the cost of the network within you budget.  You may not want to run fiber to each desktop because it is a lot cheaper to run CAT V and the speed of fiber isn't needed and would be wasted on each user.  These wire types haven't been discussed in the course yet.  They will be covered in Chapter 3

    • Immediate Costs - The things you will need to buy right away.  For example, new computers, or upgrades for current computers. 

    • Recurring Costs - Costs that repeat, such as network managers salaries, Internet fees, maintenance agreements etc...

  • Number of Workstations - The number of workstations that you will need on a network will be a factor in the type of network you have.  For example, if you have 3 computers on a network a workgroup may be a good solution.  If you have more then 10 Microsoft recommends that you move to a domain environment.  More on this in Chapter 7.

  • Type of Workstations - If you have all Macintosh computers you may choose a different network setup then if you have all PC's.

  • Number of Concurrent Users - As you add more users to your network there will be more traffic.  If you are going to have a lot of users on at once you are going to want to pick a LAN that will accommodate the traffic.

  • Type of Use -  If you have a lot of users on at once and each user is doing very little work on the network you would choose one type of network.  If you have the same number that is continuously updating a database on the network you will need a network that will handle that amount of traffic.

  • Number and Type of Printers - Some server software will only support a limited number of printers.  You will also want to make sure there are drivers for the server software you pick.

  • Distance and Medium - You want to make sure you have the right type of medium.  You may have to choose Fiber to solve distance problems or Shielded twisted pair to solve interference issues.

  • Speed - The speed that is quoted by the vendor is not always the actual speed that the device transmits at continually. 

  • Applications - Will the software you have or want to run work on the LAN you are installing.

  • Expandability - Will you be able to add to the network you are creating?

  • Device Connectivity - Will all of your devices connect to the network?

  • Connectivity to Other Networks - Will you be able to connect to another LAN / WAN / Internet?

  • LAN Software and Hardware - Will this work on your existing equipment?

  • Adherence to Established Standards - There are a lot of standards in local area networks.  You will want to make sure that the network you choose will follow these standards.  But sometimes that isn't possible.  Suppose you want to take advantage of a new feature that hasn't become a standard.  You may have to use a vendors solution.  A lot of times you will find that a lot of vendors will use the same solution which eventually become a standard.

  • Vendor and Support - You want to purchase your supplies from a good vendor that will support what they sell you.  You have to ask if they are it for the sale or there for the support as well.

  • Manageability - Managing a LAN is a time consuming thing, even if it is a small network.  You will want to make sure the server software you choose has tools that will allow you to manage it easily.

  • Security - On a LAN security is an issue.  You will want to make sure you can setup security in your server software.  More on this in Chapter 7.

More Information


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