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C-4
BASIC FDDI NETWORKS
CONCENTRATOR 3
WRAP
CONCENTRATOR 2
CONCENTRATOR 1
CONCENTRATOR 4
PRIMARY
RING
SECONDARY
RING
A B
A
B
A
B
A
B
Figure C-2. Wrapping a Broken Ring
ANSI Standard X3T9.5
The X3T9.5 standard is divided into five sections: Station
Management (SMT), Media Access Control (MAC), two Physical
Layer Medium Dependent (PMD) standards (one for multimode fiber
and another, SMF-PMD, for single mode fiber) and a Physical Layer
Protocol (PHY). Each section defines a unique entity of the FDDI
station architecture and its operation.
Note: Single mode operation is very similar to multimode operation.
Since the principle difference is the characteristics of the optic
transceivers and fiber optic medium, only the multimode PMD is
discussed here.
The entities described by X3T9.5 perform many of the functions
required in the lower layers of the OSI network model Data Link and
Physical Layers (Figure C-3).