Cabletron Systems manual Appendix a Basic Fddi Networks, BRIM-F6 User’s Guide A-1

APPENDIX A

BASIC FDDI NETWORKS

This Appendix covers basic Fiber Distributed Data Interface (FDDI) network concepts relating to FDDI network design and installation.

ANSI Standard X3T9.5 provides greater detail on FDDI access methods. Reference this standard whenever you need more complete information. Specific areas presented here include:

•Basic FDDI Concepts

•FDDI Devices

•Design and Installation Considerations.

A.1 Basic FDDI Concepts

An FDDI network provides a high-speed (100 Mbit/sec.), fiber optic network capable of reliable data transmission. The fiber optic media provides increased bandwidth, immunity from electrical noise, security, and permits the use of longer cable segments. These features make FDDI a viable alternative in LAN backbone applications, or as a back-end or front-end network between processors.

A.2 FDDI Media Access Protocol

The FDDI standard X3T9.5 describes the media access and token passing protocol for FDDI networks. Each station on an FDDI ring has a unique station address, differentiating it from all other stations. A special frame, called a token, controls transmission.

Only one station, the station holding the token, can transmit at any given time. This token circulates around the ring from station to station. Each station receives the token from the station preceding it on the ring, retains it while transmitting data (frames) and then passes (transmits) the token on to the next active station on the ring.

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