Masters of the LAN Universe: The IEEE 802 Committee
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The key to the development of the LAN market is the availability of a low-cost interface. The cost to connect equipment to a LAN must be much less than the cost of the equipment alone. This requirement, plus the complexity of the LAN logic, dictates a solution based on the use of chips and very-large-scale integration (VLSI). However, chip manufacturers are reluctant to commit the necessary resources unless there is a high-volume market. A widely accepted LAN standard assures that volume and also enables equipment from a variety of manufacturers to intercommunicate. This is the rationale of the IEEE 802 committee.
The committee issued a set of standards, which were subsequently adopted in 1985 by the American National Standards Institute (ANSI) as American National Standards. These standards were subsequently revised and reissued as international standards by the International Organization for Standardization (ISO) in 1987, with the designation ISO 8802. Since then, the IEEE 802 committee has continued to revise and extend the standards, which are ultimately adopted by ISO.
The Structure of the LAN Standards
Two conclusions were quickly reached by the committee. First, the task of communication across the local network is sufficiently complex that it needs to be broken up into more manageable subtasks. Accordingly, the standards are organized as a three-layer protocol hierarchy. Logical link control (LLC) is responsible for addressing and data-link control. It is independent of the topology, transmission medium, and medium access-control technique chosen, and was issued as a separate standard. Below logical link control are the medium access control (MAC) and physical layers. Because of the interdependence between medium access control, medium, and topology, these layers were organized into standards based on the medium access-control algorithm, with the physical layer specified as part of the medium access-control standard.
Second, no single technical approach will satisfy all requirements. The second conclusion was reluctantly reached when it became apparent that no single standard would satisfy all committee participants. There was support for various topologies, access methods, and transmission media. The response of the committee was to standardize all serious proposals rather than attempt to settle on just one. The current state of standardization is reflected by the various subcommittees in IEEE 802 and the work that each is doing.