Consider a situation where many employees in an organization need to work with the same data. This data can be stored in a central location (server), thus saving disk space on computers and allowing centralized access to shared data. A network is a group of connected computers that allows people to share information.

Roles of Computers in a Network

• Clients:
  
  
  Client computers (users' computers) make requests for services or data on the network from computers referred to as servers.
  
  
  
• Servers:
  
  
  Servers are comptuters that provide services and data to client computers. The servers in a network perform a variety of complex tasks.
  
  
  
• File and Print Servers:
  
  
  File and print servers provide file and printer resources from a centralized location. When a client sends a request for data to the file and print server, the entire database or file is downloaded to the computer making the request.
  
  
  
• Database Servers:
  
  
  Database servers can store large amounts of data in a centralized locations and make this data available to users so that they do not need to download the entire database. With a database server, the entire database stays on the server and only the results of a request are downloaded to the computer making the request.
  
  
  
• Mail Servers:
  
  
  Mail servers operate like database servers in that there are separate server and client applications, with data selectively downloaded from the server to the client. Mail servers manage the e-mail services for the network.
  
  
  
• Fax Servers:
  
  
  Fax servers manage fax traffic into and out of the network by sharing one or more fax modems. This makes a fax service available to anyone on the network without having to install a fax machine on everyone's computer.
  
  
  
• Directory Services Server:
  
  
  Directory services servers provide a central location to store information about the network, including the identity of the users accessing the network and the names of the resources available in the network. This enable network security to be administered centrally.
  
  
  

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Types of Networks

     Based on how the computers in a network are configured and how they access information, network are classified into two types: peer-to-peer and client-server.

• Peer-to-Peer Networks:
  
  
  In a peer-to-peer network, there are no dedicated servers, and there is no hierarchy among the computers. All computers are equal and therefore are known as peers. Peer-to-peer networks are also called workgroups. The term workgroup describes a small group of individuals, typically 10 or fewer, who work together.
  
  
  
• Client-Server Networks:
  
  
  As a network grows, a peer-to-peer network will probably not be able to meet the increased demand on shared resources. A client-server network consists of both servers which provide network tasks, and clients which have a reduced workload due to the servers.
  
  
  

     The scope of a network refers to its geographical size. A network can range in size from just a few computers in one office to thousands of computers linked together over great distances. Network scope is determined by the size of the organization or the distance between users on the network. The scope determines how the network is designed and what physical components are used in its construction.

There are two general types of network scope:

• Local Area Network: A local area network (LAN) connects computers that are located near each other. A corporate network that includes serveral adjacent buildings can also be cosidered a LAN.
  


• Wide Area Network: A wide area network (WAN) connects a number of computers located at a greater distance from one another. A WAN can be made up of a number of interconnected LANs. The Internet for example is really a WAN.