Components of a Network
Computer Science Revision
A switch is a telecommunication device that receives a message from any device connected to it and then transmits the message only to the device for which the message was meant. This makes the switch a more intelligent device than a hub (which receives a message and then transmits it to all the other devices on its network). The network switch plays an integral part in most modern ethernet local area networks (LANs). Mid-to-large sized LANs contain a number of linked managed switches. Small office/Home office (SOHO) applications typically use a single switch, or an all-purpose converged device such as a residential gateway to access small office/home broadband services such as DSL or cable internet. In most of these cases, the end-user device contains a router and components that interface to the particular physical broadband technology. User devices may also include a telephone interface forVoIP.
An Ethernet switch operates at the data link layer of the OSI model to create a separate collision demain for each switch port. With 4 computers (e.g., A, B, C, and D) on 4 switch ports, any pair (e.g. A and B) can transfer data back and forth while the other pair (e.g. C and D) also do so simultaneously, and the two conversations will not interfere with one another. In full duplex mode, these pairs can also overlap (e.g. A transmits to B, simultaneously B to C, and so on). In the case of a repeater hub they would all share the bandwidth and run in half duplex, resulting in collisions, which would then necessitate retransmissions.
In most common use, a server is a physical computer dedicated to run one or more services (as a host), to serve the needs of the users of other computers on a network. Depending on the computing service that it offers it could be a database server, file server, mail server, print server, web server ,gaming server, or some other kind of server.
In the context of client server achitecture, a server is a computer program running to serve the requests of other programs, the "clients". Therefore, the server performs some computational task on behalf of "clients." The clients either run on the same computer, or they connect through the network.