FIBER DISTRIBUTED DATA INTERFACE (FDDI)

                 FDDI Topology

·         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.