19.2. Clients and servers of local networks

The well-known idea of ​​resource sharing is the basis for the widespread use of local area networks of computers. High bandwidth of local networks provides efficient access from one node of the local network to resources located at other nodes.

The development of this idea leads to a functional allocation of network components: it is reasonable not only to have access to the resources of a remote computer, but also to receive from this computer some service that is specific to resources of this kind and software for which it is not advisable to duplicate in several nodes. So we come to the distinction of workstations and servers of the local network.

The workstation is intended for the immediate work of a user or category of users and has resources that meet the local needs of the user. The specific features of a workstation can be the amount of RAM (not all categories of users need large RAM), the presence and amount of disk memory (diskless workstations using external memory of the disk server are quite popular), processor and monitor characteristics (some users need a powerful processor, others are more interested in the resolution of the monitor, for others, the means of speeding up graphics are required, etc.). If necessary, you can use the resources and / or services provided by the server.

The server of the local network should have the resources corresponding to its functional purpose and network needs. Note that in connection with the orientation towards the open systems approach, it is more correct to speak of logical servers (having in mind a set of resources and software tools that provide services over these resources), which are not necessarily located on different computers. A feature of the logical server in an open system is that if, for reasons of efficiency, the server should be moved to a separate computer, this can be done without the need for any alteration of both the application itself and the applications using it.

Examples of a server are:

• telecommunications server providing communication services of this local network with the outside world;
• a computer server that makes it possible to perform calculations that cannot be performed on workstations;
• a disk server that has extended external memory resources and provides them for use by workstations and, possibly, other servers;
• a file server that supports shared file storage for all workstations;
• the database server is actually a normal DBMS that receives requests over the local network and returns results.

The local network server provides resources (services) to workstations and / or other servers.

It is customary to call a local network client requesting services from some server and a server — a component of the local network that provides services to some clients.