Cabletron Systems manual Reliability, BRIM-F6 User’s Guide A-3

Reliability

Ethernet/802.3

Network

Ethernet/802.3

Network

ETHERNET to

FDDI BRIDGE

		File
ETHERNET		Server
		DUAL
to FDDI	FDDI
		ATTACHED
BRIDGE	NETWORK	STATION

DUALATTACHED

CONCENTRATOR

SINGLE ATTACHED

CONCENTRATOR

Single Attached

Stations

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.

BRIM-F6 User’s Guide Page A-3