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Components
A computer network is multiple computers connected together using a
telecommunication system for the purpose of communicating and sharing resources.
Experts in the field of networking debate whether two computers that are
connected together using some form of communications medium constitute a
network. Therefore, some works state that a network requires three connected
computers. For example, "Telecommunications: Glossary of Telecommunication
Terms" states that a computer network is "A network of data processing nodes
that are interconnected for the purpose of data communication", the term
"network" being defined in the same document as "An interconnection of three or
more communicating entities". A computer connected to a non-computing device
(e.g., networked to a printer via an Ethernet link) may also represent a
computer network, although this article does not address this configuration.
Basic components of computer networks
Computers
Many of the components of an average network are individual computers, which are
generally either workstations (including personal computers) or servers.
Types of workstations
There are many types of workstations that may be incorporated into a particular
network, some of which have high-end displays, multiple CPUs, large amounts of
RAM, large amounts of hard drive storage space, or other enhancements required
for special data processing tasks, graphics, or other resource intensive
applications. (See also network computer).
Types of servers
The following lists some common types of servers and their purpose.
File server
Stores various types of files and distributes them to other clients on the
network.
Print server
Controls and manages one or more printers and accepts print jobs from other
network clients, spooling the print jobs, and performing most or all of the
other functions that a workstation would perform to accomplish a printing task
if the printer were connected directly to the workstation's printer port.
Mail server
Stores, sends, receives, routes, and performs other email related operations for
other clients on the network.
Fax server
Stores, sends, receives, routes, and performs other functions necessary for the
proper transmission, reception, and distribution of faxes.
Telephony server
Performs telephony related functions such as answering calls automatically,
performing the functions of an interactive voice response system, storing and
serving voice mail, routing calls between the Public Switched Telephone Network
(PSTN) and the network or the Internet (e.g., voice over IP (VoIP) gateway),
etc.
Proxy server
Performs some type of function on behalf of other clients on the network to
increase the performance of certain operations (e.g., prefetching and caching
documents or other data that are requested very frequently) or as a security
precaution to isolate network clients from external threats.
Remote Access Server (RAS)
Monitors modem lines or other network communications channels for requests to
connect to the network from a remote location, answers the incoming telephone
call or acknowledges the network request, and performs the necessary security
checks and other procedures necessary to log a user onto the network.
Application server
Performs the data processing or business logic portion of a client application,
accepting instructions for operations to perform from a workstation and serving
the results back to the workstation, while the workstation performs the user
interface or GUI portion of the processing (i.e., the presentation logic) that
is required for the application to work properly.
Web server
Stores HTML documents, images, text files, scripts, and other Web related data
(collectively known as content), and distributes this content to other clients
on the network on request.
Backup server
Has network backup software installed and has large amounts of hard drive
storage or other forms of storage (tape, etc.) available to it to be used for
the purpose of ensuring that data loss does not occur in the network.'''
Printers
Many printers are capable of acting as part of a computer network without any
other device, such as a print server, to act as an intermediary between the
printer and the device that is requesting a print job to be completed.
Thin Clients
Many networks use thin clients instead of workstations either for data entry and
display purposes or in some cases where the application runs entirely on the
server.
Other devices
There are many other types of devices that may be used to build a network, many
of which require an understanding of more advanced computer networking concepts
before they are able to be easily understood (e.g., hubs, routers, bridges,
switches, hardware firewalls, etc.). On home and mobile networks, connecting
consumer electronics devices such as video game consoles is becoming
increasingly common.
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