Several protocol controllers for the IEEE 802 local area networks are surveyed and some characteristics for classifying them are given. Some case studies from these controllers are given as illustrations. Two new developments-the protocol engine and the programmable protocol engine-are also described. The protocol engine, currently under development, implements a new protocol called XTP which performs the functions of both the network and transport layers. The programmable protocol engine can implement several connection-oriented protocols by changing contents of a programmable random access memory.
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