Network Interface Unit (NIU)

Network Interface Unit (NIU) as a component of LAN

The network interface unit is a microprocessor-based device containing hardware and software which supply the intelligence to control access and communication across the network and to perform all communication processing. It is the means by which the workstations are connected functionally and physically to the network.

On most microcomputer, the network interface is a printed circuit board installed in the microcomputer. On some networks, the network interface may be implemented as a stand-alone box, termed a wiring center, or hub, attached between the main network cable and the workstation.

Network interface functions are realized through chips on the interface unit: Network bus drivers, communication controller chips, specialized microprocessors, RAM buffers and ROM code are executed by the workstation itself. For most LANs, the network interface unit for all user workstations is identical. Server interface units may include additional ROM code to implement additional functions. Physical connection to the network is provided through a standard communication or input/output interface.

Through the network interface, data on the medium is available to all attached workstations and peripherals. System users never need to know what it takes to get from one point to another; they simply indicate the desired destination. The network interface unit provides transmission and data control, formats the data into manageable units, translates the data rate and protocols of the attached workstation to the network communication medium and vice versa, and supplies address recognition capabilities. Details of network operation are hidden from users of the attached workstations.

Network Interface can be classified in to the communication interface, containing network oriented functions and the host interface, containing computer specific functions.

The communication interface is the unit which logically interfaces to the network. It performs all transmission related functions. It accepts data from the attached workstations, buffers the data until the communication channel is available and then transmits the data. The communications interface also monitors the channel for messages addressed to its workstation, stores the data and transfers the data to the device.

The host interface supplies the connection between a specific workstation's internal circuitry and the communication interface unit. It fits into the input/output structure of a particular computer and governs all data exchange between the workstation and the communication-oriented portion of the network interface.