In the computer communication system, a communication mechanism is created for the attached host through network interface unit (NIU). As the demand for data communications grows, the need for intelligent NIU also increased. Most NIUs currently used, however, are somewhat dim in the sense that most communication overhead is burdened to main CPU in the host. By modifying the architecture of the whole system, including host and communication subsystem, we can enhance the throughput of system remarkably. It can be achieved by the way of providing some intelligence to the NIU itself. The intelligent NIU now supports for all of the physical, data link, network and transport layers of the ISO/OSI model for communications protocols. This support off loads much of the protocol processing activity from the host, allowing higher throughput and greater CPU availability.