This chapter provides a framework from which we can go on to describe performance evaluation of local area networks (LANs). It also provides a description of what constitutes a LAN, how it is used, and for what purposes, and gives details of LAN topologies. The chapter examines the basic types of LAN topology: the ring, bus, star, regular interconnects, and hybrid in greater detail. It explains the three basic classes of communications control protocols: contention based, reservation based, and sequential based. Contention-based control protocols are based on the interaction of interface units with each other to acquire the network media for service. The chapter also reviews some of the basic concepts of structure, operations and management. The levels of database management served by LANs include: No support, File transfer, Remote file management, Local data managers, Remote service to local data manager, and Integrated distributed database manager.