Network systems

All network communications involve the use of hardware and software. The system hardware and software communications support is determined by the hardware being used and the software necessary to run that hardware and interface with the network.

Hardware consists of the physical equipment connected to the physical network. Software consists of the programs and device drivers pertaining to the operation of a particular system. The system hardware consists of adapter cards or other devices that provide a path or interface between the system software and the physical network. An adapter card requires an input/output (I/O) card slot in the system. The adapter card connects the data terminal equipment (DTE) to the data circuit-terminating equipment (DCE); that is, it provides physical local addressing to a DTE port. Other devices, such as modems, can be attached to one of the standard ports on the computer.

An adapter card prepares all inbound and outbound data; performs address searches; provides drivers, receivers, and surge protection; supports different interfaces; and in general relieves the system processor of many communications tasks. Adapter cards support the standards required by the physical network (for example, EIA 232D, Smartmodem, V.25 bis, EIA 422A, X.21, or V.35) and may, at the same time, support software protocols, for example, synchronous data link control (SDLC), high-level data link control (HDLC), and bisynchronous protocols. If the adapter does not contain software support, then this support must be provided by the adapter device driver.