คำหลัก : lan,lan,local area network,internet,intranet
Reference: techweb.com
LAN
(Local Area Network) A communications network that serves users within a confined geographical area. It is made up of servers, workstations, a network operating system and a communications link.
Servers are high-speed machines that hold programs and data shared by network users. The workstations (clients) are the users' personal computers, which perform stand-alone processing and access the network servers as required (see client/server).
Diskless and floppy-only workstations are sometimes used, which retrieve all software and data from the server. Increasingly, "thin client" network computers (NCs) and Windows terminals are also used. A printer can be attached locally to a workstation or to a server and be shared by network users.
Small LANs can allow certain workstations to function as a server, allowing users access to data on another user's machine. These peer-to-peer networks are often simpler to install and manage, but dedicated servers provide better performance and can handle higher transaction volume. Multiple servers are used in large networks.
The controlling software in a LAN is the network operating system (NetWare, UNIX, Windows NT, etc.) that resides in the server. A component part of the software resides in each client and allows the application to read and write data from the server as if it were on the local machine.
The message transfer is managed by a transport protocol such as TCP/IP and IPX. The physical transmission of data is performed by the access method (Ethernet, Token Ring, etc.) which is implemented in the network adapters that are plugged into the machines. The actual communications path is the cable (twisted pair, coax, optical fiber) that interconnects each network adapter. See WAN.
Clients and Servers in a LAN This illustration shows one server for each type of service on a LAN. In practice, several functions can be combined in one machine and, for large volumes, multiple machines can be used to balance the traffic for the same service. For example, a large Internet Web site is often comprised of several computer systems (servers).
The Software in a Network Client This shows the various software components that reside in a user's client workstation in a network.
The Software in a Network Server This shows the network operating system and various system software components in a network server.
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