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Key Concepts 89
Key Concepts
Before you implement FDDI in your system, review the following FDDI
standards, key concepts, and key terms.
Related Standards The industry guideline for FDDI technology is divided into four major
standards:
■
Physical Medium Dependent (PMD) — Specifies the characteristics
of the fiber-optic medium, the connectors that attach stations to the
fiber-optic medium, the transmission wavelength, the power
requirements for transmitters, and the methods for optically bypassing
inactive stations.
■
Physical (PHY) — S
pecifies data encoding and decoding, clock speed
and clocking scheme, data framing, and the control symbols used in
the network.
■
Media Access Control (MAC) — S pecifies access to the medium,
token passing, addressing, data checking, frame generation and
reception, error detection and recovery, and the bandwidth allocation
among the stations.
■
Station Management (SMT) — S pecifies the FDDI station and ring
configurations, initialization and maintenance of station-to-station
connections, and the control required for the proper operation of
stations in an FDDI ring.
These four standards are always described in relation to the Open
Systems Interconnection (OSI) Reference Model. This model was
established by the International Standards Organization (ISO) to
standardize digital data communications. Each FDDI station is made up of
logical entities that conform to the four standards. These entities
represent the active services or management elements within OSI.