An Introduction to Local Area Networks

1. An Introduction to Local Area Networks An Overview of Peer-to-Peer and Server-Based Models

2. The simplest form of networking occurs when two computers are connected together with a cable to share data. The far-reaching networks that we use today were born from this simple but revolutionary idea.

3. Before the advent of networks: Each computer had to have its own software and hardware installed, greatly increasing the total cost of ownership. Information was shared between computers by “sneaker net”, where the users would carry a floppy disk from one computer to another.

4. Stand-alone computer systems are both expensive and hard to manage because each system must have its own resources: • Floppy disks • Hard disks • CD-ROM drives • Printers • Modems and Faxes • Software

5. When computer systems are networked, they can share: • Software • Data • Printers • Storage systems • Faxes and Modems • Backup systems • Other hardware resources

6. Although networks such as the Internet connect computers throughout the world, most networks are local area networks (LANs). These are networks that are installed by organizations to share resources at one location of the organization.

7. Local area networks generally consist of these resources: • Servers - computers that provide resources to the network • Client computers - computers that access resources from the network • Media - the cabling that connects the network • Shared software applications • Shared data • Shared peripherals - printers, storage devices, communications devices, and other resources

8. There are only two basic types of computer networks. All computer networks are a variation or a combination of these two types: • Peer-to-Peer • Server-based

9. The choice of which network model to deploy is based on many factors: • The number of computers which must be networked • The level of security necessary • The amount of network traffic • The needs of the users • The support staff available • The budget allocated for the network

10. In the peer-to-peer model, each user acts as the administrator for their own workstation. They grant the use of resources to other users by adding the other users to their local database of users and giving the other users permission to use files and hardware resources located on their computer.

11. A peer-to-peer network is typically implemented when: • There are 10 or less users of the network • Security is not an important issue • All of the users are located in the same area • The networking needs of the organization are not expected to grow • There is a limited budget for network support personnel

12. The peer-to-peer model has some advantages: • Low cost – networking is built in to the operating system of the computers • Easy to implement – cabling is generally inexpensive, simple and visible • No stand-alone server to install and configure • Low system administration costs – each user acts as the administrator of their workstation

13. There are also disadvantages to the peer-to-peer model: • Low level of security • Users must be created and permissions must be granted on each computer on the network • Each user must be trained in the administration of their workstation • Low levels of performance – each computer acts as both a workstation and a server • Data is spread out over many different computers making it harder to administer and back up

14. The server-based model is generally used when there are more than 10 users on the network and is always employed for mission-critical applications. In the server-based model, the network has one or more dedicated server computers.

15. Network server computers: • Serve files and applications • Provide hardware resources such as printers, plotters, faxes and modems • Provide centralized storage of programs and applications • Allow for secure, centralized management of user accounts and files

16. There are many types of specialized servers. A typical LAN may be constructed of: • File servers – servers that provide applications and data to the client computers • Applications servers - servers that run applications such as databases – the information is processed on the server and the results are sent to the client • Mail servers – servers that provide electronic mail access and storage • Fax servers – servers that manage multiple fax boards to provide fax capabilities to each user • Communications servers – servers which provide communications with external networks such as the Internet

17. The server-based model has many advantages: • Security – policies may be set by the system administrator and applied to all users of the system. File permissions may be applied to individual files • Sharing resources – hardware and software resources may be shared by all users – management of these resources is centralized on the server • Backup – centralized data storage allows for easier backup of important files • Redundancy – programs and data may be stored on backup servers so that they are available even if the main server fails • Support for a large number of users – may support thousands of users

18. Disadvantages of the server-based model: • More expensive – requires at least one dedicated server and a network operating system • Administration costs - continuing costs for employees to manage the network • Installation – the wiring of the network is more complex using switches, routers, and hubs

19. The peer-to-peer model should be chosen when: • Network security is not an important issue • There are 10 or less users of the network • The budget for the network is limited • The users are all in one small area • The company and the network are unlikely to expand • There is limited technical support available

20. The server-based model should be chosen when: • The network is mission-critical • Network security is a primary consideration • Data redundancy and backup are important • Many types of services are required • There are more than 10 users of the network • The company and the network is likely to expand • The budget is available to provide network support personnel

21. An Introduction to Local Area Networks © Stephen M. May 1998