- 100mbps
- normally implemented over fiber optic (fast-Ethernet, UTP)
- dual redundancy built in by use of primary and secondary ring
- automatic bypassing and isolation of faulty nodes
Fiber Distributed Data Interface
FDDI is based on two counter rotating 100-Mbit/sec token-passing rings. The
rings consist of point to point wiring between nodes which repeat the data as it
is received.
The primary ring is used for data transmission; the secondary is used for
data transmission or to back up the primary ring in the event of a link or
station failure. FDDI supports a sustained transfer rate of about 80Mbps, a
maximum of 1000 connections (500 nodes) and a total distance of 200 kilometers
end to end. There is a maximum distance of 2 kilometers between active nodes.
FDDI Station Types
There are two main types of stations, class A which attach directly to dual
rings; or class B which attach to a station acting as a concentrator.
A concentrator is a specialized workstation that attaches to the ring and has
multiple ports that allow attachment of other devices in a physical star
configuration. These may be cascaded.
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