• Terms
• Configurations
• Strategies
• Network Types

Terms

• Node - any device connected to a network such as a computer, printer or data storage device.
    
• Client - a node that requests and uses resources available from other nodes.   Example a web browser that request web pages from web servers.
    
• Server - a node that provide services and resources to other nodes.  Examples are Print Servers, File Servers, Web Servers, and Database Servers. 
    
• Network Operating System - the operating system of the network that allow resources and information to be shared.  Examples are Novell Netware and Microsoft Windows NT.
    
• Distributed Processing - a network architecture that distribute processing power to multiple computers on the network.  This architecture is commonly used by decentralized organizations.
    
• Host Computer -  a large centralized computer that host all or most of the applications used by a centralized organization.  For example an airline reservation system require a centralized host computer that maintains a database containing the status of each flight and each seat.
    

Configurations

A network can be arranged or configured in several different ways.  This arrangement is called the network's topology.  The four principal networks topologies are:

• Star Network
  
  • All communications pass through the central computer.
  • The central computer can be a host computer or a file server.
  • Control is maintained by polling.
  • Can be used to provide a time sharing system.
  • Commonly used to link microcomputers to a mainframe.
      
     
• Bus Network
   
  
  • Each device on the network handles its own communications control.
  • The is no host computers.
  • All communications travel along a common connection cable called a bus.
  • Commonly used for sharing data stored on different microcomputers.
  • Not as efficient as the star network but is less expensive.
      
      
• Ring Network
   
  • Each device is connected to two other devices, forming a ring.
  • There is no central file server or computer.
  • Messages are passed around a ring until they reach their destination.
  • Often used to link mainframes, especially over wide geographical areas.
  • Useful in decentralized organizations.
      
      
• Hierarchical Network
   
  • Consists of several computers linked to a central host computer (similar to star networks).
  • Other computers are also hosts to other, smaller computers.
  • Allows various computers to share databases, processing power, and different output devices.
  • Useful in centralized organizations.

Strategies

Every network has a strategy, or way of coordinating the sharing of information and resources.  The most common network strategies are:  

• Terminal Network Systems
  • Processing power is centralized in one large computer, usually a mainframe.  With connecting nodes (usually display terminals or microcomputers) acting as terminals that only display information from the centralized computer.  A special terminal emulation software can be used by a microcomputer to make it look to the central computer as a display terminal.
  • Star and Hierarchical networks are typical configurations.
  • Commonly used in airline reservation systems.


  
   
  
• Client/Server Network Systems
  • Clients request services.
  • Severs  provide services.
  • Servers are usually powerful computers that provides access to centralized resources such as databases, application software, and hardware.

 

  
   
  
   
• Peer-to-Peer Network Systems
  • Nodes can act as both servers and clients.
  • Bus network is a typical configuration.
  • Network is inexpensive and easy to install.
  • Work well for small systems with less than ten nodes.
  

  
   

Network Types

Communication networks differ in geographical size.  Three important types are:

• Local Area Networks
  • Typically links computers using a bus network
  • Allow users to share hardware, software, and data
  • Network bridge devices may be used to link LANs to other networks with the same configuration.
  • Network gateway devices may be used to link LANs to other networks, even if their configurations are different.
      
• Metropolitan Area Networks
  • Used to link networks located in different office buildings in a city.
  • Cellular phones systems expands the network by linking portable computers using car and portable phones. 
      
• Wide Area Networks
  • Typically use microwave relays and satellites to reach users over long distances.
  • The widest of all WANs is the Internet, which spans the entire globe.
     

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