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Reliability
BRIM-F6 User’s Guide Page A-3
Figure A-1. Typical FDDI Physical Installation
A.3 Reliability
FDDI networks employ a ring topology and are inherently vulnerable to
the frailties of each ring segment and failures of individual stations. The
ring of trees topology reduces the risk of a single node bringing the entire
network down.
A redundant data path, within the main ring trunk cabling, further reduces
this vulnerability. In theory, to achieve the circular data flow, the ring
topology requires media that allows only one-way traffic. In practice, an
FDDI ring uses media that provides two fiber optic ring paths, a primary
ring and a secondary ring. The secondary ring restores the continuity of
the ring in the event a node fails node or a trunk segments (a trunk cable
breaks). Figure A-2 illustrates how the open ends of the primary ring
wrap into the secondary ring, restoring continuity by creating a new ring.
Ethernet/802.3
Network
FDDI
NETWORK
Ethernet/802.3
Network
DUAL ATTACHED
CONCENTRATOR
ETHERNET to
FDDI BRIDGE
ETHERNET
to FDDI
BRIDGE
SINGLE ATTACHED
CONCENTRATOR
Single Attached
Stations
File
Server
DUAL
ATTACHED
STATION
BRIM-F Book Page 3 Monday, January 29, 1996 9:26 AM