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Network Architecture
Network Architecture
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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