A computer network is a grouping of two or more computers to share data, applications, and networked peripherals such as printers.
Employees at all but the tiniest companies depend on the network to conduct their daily tasks. Local area networks (LANs) link computers in the same building via wires, while wide area networks (WANs) connect geographically dispersed computers by radio wave or telephone line (Frame Relay WANs use the latter). Many companies are also implementing wireless LANs (WLANs) to give employees and customers the flexibility of working in conference rooms and common areas without being tethered to a desk.
Much like buildings, networks must be designed before they can be built. The network design specifies the network infrastructure, including:
Network topology. The topology is a layout that dictates how the computers will be connected. Common network topologies include a star, a bus, and a ring.
Network protocol. This is the format the data takes as it passes over the network connection. The protocol determines how the computer sends and receives messages and what type of data compression is used. Ethernet is one of the most popular protocols, supporting data-transfer rates of up to 10 megabits per second.
Network architecture. The network architecture can take one of several forms, including peer-to-peer (in which each computer or node on the network has equal capabilities) and client/server (in which one node, the server, is more powerful and manages network functions for the client, or PC, devices).
The network architect must utilize the right mix of technology to provide adequate network bandwidth for the network users' needs. Network bandwidth is the amount of data that can be transmitted on a network in a particular amount of time. Video- and graphic-intensive applications require higher bandwidth than simple text-based programs. Bandwidth management software helps identify and alleviate network bottlenecks. Network administrators also use load balancing to allocate network bandwidth to compute-intensive applications so they won't bring down overall network performance.
Many companies are choosing to install fiber-optic cables to transmit data on their network as fiber optic technology is capable of much higher data throughput than conventional metal cables.
Another critical network feature is fault tolerance, which is the network's ability to recover from an unexpected failure. Since a company's revenue and reputation often ride on its network, many companies employ multiple layers of fault tolerance. These range from a backup power source in case of an electrical power outage to mirroring the data from one server onto another server that will automatically take over ("fail over") in case of failure. Network clusters are also used to prevent unexpected data loss.
With the network design and installation complete, the focus shifts to network management and maintenance. Network administrators must ensure the network operates reliably, that its performance or speed is adequate, and that it is secure from unwanted intrusion. With the advice of internal or external security professionals, network administrators use techniques and technology, including firewalls and user authentication, to ensure data stored on a computer on the network cannot be read without proper authorization.