1. © 2001 by Prentice Hall 2-1 Local Area Networks, 3rd Edition David A. Stamper Part 1: Introduction to Data Communications and Local Area Networks Chapter 2 Introduction to Local Area Networks

2. © 2001 by Prentice Hall 2-2 Chapter Preview Reasons organizations use networks Popular network applications Distinguishing features of LANs Situations in which a LAN can be useful Added management responsibilities when using a LAN LAN selection criteria In this chapter you will study:

3. © 2001 by Prentice Hall 2-3 Why Use LANs? Resource Sharing – The need to share resources is still one of the primary reasons for using a network. – Dedicating resources (disk drives, tape drives, printers, data, application programs, scanners, etc.) to each user is expensive. In a network, some or all of these resources may be shared. Communication – We use data communications networks for communications, but the objects that are communicating are not always people. – A person-to-person communication may be an electronic conversation with the two parties exchanging messages in real time. – An application-to-application dialogue may be the transfer of a file from one node to another.

4. © 2001 by Prentice Hall 2-4 Why Use LANs? (cont.) Management Control – A LAN can help standardize the microcomputer environment. – Application standards can be set up more easily in a network because most application programs—for example, word processors and spreadsheet programs— can be installed on one or more network nodes called servers. – LANs can also help control computer viruses. A diskless workstation, as the name implies, has no local disk drives. This reduces the ways in which a virus can be introduced.

5. © 2001 by Prentice Hall 2-5 Why Use LANs? (cont.) Cost Effectiveness – The ability to share resources has a direct impact on an organization’s expenses. If users can share hardware, less hardware is needed. – The less obvious cost effectiveness comes from the ability of users to communicate and thus improve their productivity. Downsizing – In some companies, LANs have been used to downsize the data processing hardware, software, and personnel requirements.

6. © 2001 by Prentice Hall 2-6 Why Use LANs? (cont.) New Application Software – One of the newer application technologies associated with networks is called groupware —applications oriented toward improving the productivity of a group of people working together. – Groupware automates work functions that require the communication and collaboration of two or more individuals. These tools raise office productivity and make LANs even more cost effective.

7. © 2001 by Prentice Hall 2-7 Application Software: Personal Productivity Applications Word Processing and Desktop Publishing – It is reasonable to assume that future versions will allow several users to pull out sections of a single document; allow one user to update a document and let others concurrently view but not change it; and allow users to work concurrently on the same document and view or edit the document in concert. Spreadsheets – Using spreadsheets on a LAN, users can easily share templates, and multiple users can access, modify, and print completed spreadsheets. – A LAN can provide the setting for widespread sharing. At the same time, the LAN can also provide protection against unauthorized changes to spreadsheets. Applications that allow users to make more effective use of their microcomputers on a LAN include:

8. © 2001 by Prentice Hall 2-8 Application Software: Personal Productivity Applications (cont.) Database Management – A database management system (DBMS) gives you the ability to define, use, and manage data. – With LA-oriented databases, users share the database. This reduces the amount of redundant data storage that occurs when individuals maintain their own databases on stand-alone systems. Presentation Services – Graphics hardware and software can be rather expensive. A LAN allows these expensive resources to be shared, providing a cost- effective way of distributing graphics capabilities. Applications that allow users to make more effective use of their microcomputers on a LAN include:

9. © 2001 by Prentice Hall 2-9 Application Software: Workgroup Applications Electronic Mail – Today’s e-mail systems allow correspondents to exchange communications containing text, graphics, and voice images in batch or real-time mode. For many companies, e-mail has become a primary mode of communications. Electronic Appointment Calendars – One user can consult other users’ appointment calendars to find a time at which each user is available for a meeting. Electronic Filing Cabinets – E-mail and other machine-readable documents can be stored in disk folders that are equivalent to file folders in conventional filing cabinets. Applications that allow users to make more effective use of their microcomputers on a LAN include:

10. © 2001 by Prentice Hall 2-10 Application Software: Workgroup Applications (cont.) File Exchange Utilities – File exchange utilities allow files to be easily copied from one network node to another. Project Management Systems – The introduction of LAN implementations has allowed these systems to be integrated more completely into the workgroup. A manager and team member can agree on the parameters of a task, the team member can update his or her progress, and the manager can monitor the progress. Group Decision Support Systems – Group decision support systems (GDSSs) assist individuals and groups in the decision-making process and help them set objectives. Applications that allow users to make more effective use of their microcomputers on a LAN include:

11. © 2001 by Prentice Hall 2-11 Application Software: Workgroup Applications (cont.) Electronic Meeting Systems – The inclusion of networks allow participants to exchange machine- readable information in the form of graphics, text, audio, and full- motion video. Document Management Systems – Capabilities include indexing documents, finding documents based on keywords contained in the document, controlling document changes, and allowing several users to collaborate on document editing. Applications that allow users to make more effective use of their microcomputers on a LAN include:

12. © 2001 by Prentice Hall 2-12 LAN Characteristics  Transparent Use  Mixed Hardware and Software  Limited Geographical Area  High Speed  Resource Sharing  LAN Media  Communication Protocols  Local Ownership

13. © 2001 by Prentice Hall 2-13 LAN Selection Criteria Cost – For most of us, cost is an overriding constraint, an you must choose the best solution within your budget. Usually, cost is the most inflexible constraint under which you must operate, and in the final analysis the LAN must be a cost-effective solution to your problem. Number of Workstations – Each LAN is physically capable of supporting some maximum number of workstations. If you exceed that maximum number, you must make some provision for extending the maximum number. Type of Workstations – The LAN hardware and software must be compatible with the workstation used and their operating systems.

14. © 2001 by Prentice Hall 2-14 LAN Selection Criteria (cont.) Number of Concurrent Users – As the number of concurrent users goes up, so does the LAN workload. As the LAN workload increases, you have two basic choices: You can allow system responsiveness to decrease, or you can increase the work potential of the system. Type of Use – Many concurrent users may increase the LAN workload. Number and Type of Printers – Some LAN operating systems have limits on the number of network printers supported by a server.

15. © 2001 by Prentice Hall 2-15 LAN Selection Criteria (cont.) Distance and Medium – Attaining high speed over long distances can be very expensive. Thus, each LAN has a maximum distance it can cover. Speed – It is important that you select a LAN capable of meeting your performance goals. Common LAN speeds available for microcomputers are 4, 10, 16, 100, and 1,000 Mbps, and the trend is for increasing speeds. Applications – If an application uses an interface not supported by a particular LAN, then the application probably will not work on that network. Moreover some software is not LAN compatible.

16. © 2001 by Prentice Hall 2-16 LAN Selection Criteria (cont.) Expandability – After installing a LAN, you probably will need to add workstations to it or move workstations from one location to another. The ease of doing this varies among implementations. Device connectivity – Some organizations need to attach special devices to the LAN, for example, a plotter or scanner. LAN interfaces for such devices may not be available on some LANs or on some LAN file servers. Connectivity to Other Networks – A variety of connection capabilities exist, but a given LAN may not support all of them. LAN Software and Hardware – You need to select LAN software and hardware that will be compatible with your existing equipment.

17. © 2001 by Prentice Hall 2-17 LAN Selection Criteria (cont.) Adherence to Established Standards – There are several standards for LAN implementation. Some LANs conform to these standards whereas others do not. There are pros and cons of selecting either a conforming system, or a system that does not conform to standards. Vendor and Support – Your vendors ought to be able to help you in times of problems; provide you with maintenance and support; and supply you with spare parts, hardware and software upgrades, and new equipment. Manageability – During the selection process, you must ensure that your LAN will have the necessary management tools or that third-party tools are available. Third-party tools are those written by someone other than the LAN vendor.

18. © 2001 by Prentice Hall 2-18 LAN Selection Criteria (cont.) Security – Data in a LAN is shared. Sharing should not, however, imply that all users should have unlimited access to all data. The LAN software must have the ability to control access to data.

19. © 2001 by Prentice Hall 2-19 Immediate and Recurring costs of a LAN Equipment upgrades Documentation Installation of cabling System software installation Creating user environments Space required for new equipment LAN management—personnel costs Consumable supplies—toner, paper, etc. Immediate Costs Recurring Costs Training users, operators, administrators Site preparation Hardware installation Installing applications Testing Supplies and spares Hardware and software maintenance Training new users, administrators

20. © 2001 by Prentice Hall 2-20 Basic LAN Management Tasks Add, delete users and groups Set user environment Install/remove printers Maintain printers Add/change/delete hardware Plan and implement changes Make backups Carry out recovery as necessary Plan capacity needs Serve as liaison with other network administrators User/Group Oriented General Set user/group security Solve user problems Setup user/printer environment Manage print jobs Establish connections with other networks Diagnose problems Maintain operating procedures Educate users Monitor the network for problems and to gather statistics for capacity planning Printer Oriented Hardware/Software Oriented