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C-12
BASIC FDDI NETWORKS
An optical bypass switch is a device that can be inserted between a
station and the FDDI ring connections that lets you remove the
station from the ring without disturbing ring continuity. They are
usually electrically actuated and provide passive optical switching of
both the primary and secondary ring cables. Figure C-9 shows the
data paths through the switch in both the bypass and operational
(non-bypassed) states.
BYPASS STATE
Station Power Off
OPERATIONAL STATE
Station Power On
FDDI Dual
Optical Bypass
Switch
FDDI Dual
Optical Bypass
Switch
FDDI
Ring
FDDI
Ring
Station
Station
Figure C-9. Optical Bypass Switch
A concentrator is a hub. It provides connections to the dual ring for
single attached stations and controls their access to the ring. Each
main ring connection port can be optically bypassed when the
attached station is disabled or when the branch cable is disconnected.