- A network is a group of systems that are connected to allow sharing of resources— such as files or printers—or sharing of services—such as an Internet connection
- There are two aspects of setting up a network: the hardware used to connect the systems together and the software installed on the computers to allow them to communicate.
- A typical network involves having users sit at workstations, running such applications as word processors or spreadsheet programs
- The workstation also is known as a client, which is just a basic computer running a client operating system such as Windows XP or Linux.
- These users typically store their files on a central server so that they can share the files with other users on the network.
- The server is a special computer that contains more disk space and memory than are found on client workstations. The server has special software installed that allows it to function as a server. This special software can provide file and print services (to allow sharing of files and printers), provide web pages to clients, or provide e-mail functionality to the company.
- The term host refers to any computer or device that is connected to a network and sends or receives information on that network. A host can be a server, a workstation, a printer with its own network card, or a device such as a router. We can summarize by saying that any system or device that is connected to the network is known as a host.
WANs, LANs, and MANs
- A local area network (LAN) typically is confined to a single building, such as an office building, your home network, or a college campus.
- A wide area network (WAN) spans multiple geographic locations and is typically made up of multiple LANs.
- The term metropolitan area network (MAN) is not used often anymore; it refers to a network that exists within a single city or metropolitan area.
Types of Networks
- A peer-to-peer network has no dedicated servers; instead, a number of workstations are connected together for the purpose of sharing information or devices. When there is no dedicated server, all workstations are considered equal; any one of them can participate as the client or the server.
- Peer-to-peer networks are designed to satisfy the networking needs of home networks or of small companies that do not want to spend a lot of money on a dedicated server but still want to have the capability to share information or devices.
- Most of the modern operating systems such as Windows already have built-in peer-to-peer networking capabilities,
- The disadvantage of a peer-to-peer network is the lack of centralized administration—with peer-to-peer networks, you need to build user accounts and configure security on each system.
- Server-Based Networks
The server in a server-based network may provide a number of different service :
- File and print servers
- Application servers
- Web servers
- Directory servers
Internet, Intranet, and Extranet
Internet, intranet, and extranet are three terms that describe “Internet-type” applications that are used by an organization, but how do you know if a web application is part of your intranet or part of the Internet?
- Internet : If you wish to expose information to everyone in the world, then you would build an Internet-type application. An Internet-type application uses Internet protocols such as HTTP, FTP, or SMTP and is available to persons anywhere on the Internet. We use the Internet and web applications as ways to extend who the application can reach. For example, I no longer need to go to the bank to transfer funds. Because the bank has built a web site on the Internet, I can do that from the comfort of my own home.
- Intranet : An application is considered to be on the company’s intranet if it is using Internet-type protocols such as HTTP or FTP but the application is available only within the company. The information on a company’s intranet would not be accessible to persons on the Internet because it is not for public use. For example, a few years ago I was sitting with my banking officer going over my account and noticed that the bank had moved all of its customer account information to a web site and that the banking officer was using a web browser to retrieve my account details. Although the application was being used by a web browser, it was still an “internal” application meant only for banking officers.
- Extranet : From time to time, an application that has been built for the company’s intranet and used by internal employees will need to be extended to select business partners or customers. If you extend your intranet out to select business partners or customers, you have created an extranet. An extranet cannot be used by anyone else external to the company except for those selected individuals