Hitachi US7070447-001 manual HiSpeed FDDI Uplink, 2. FDDI Uplink Module installed in an HS150

Draft Level—Hitachi Confidential

HiSpeed Switch Troubleshooting Guide

In a normal ring operation, an FDDI station captures a free token and transmits completely unless the token holding timer (THT) expires. As the frame traverses the ring, every station examines the frame and checks for errors. When the destination station receives the frame, it copies the frame into its buffer, sets the error, AR, and FC indicators and places the frame back onto the ring. Finally, the frame is returned to the sending station where it is stripped off the ring and the token is released.

Station Management (SMT) unique to FDDI, detects, isolates, and recovers network faults on the ring. The HiSpeed switch participates in the ring recovery process as a function of SMT. Built-in timers are used by all stations to ensure timely transmission of data across the ring. Beacon frames indicate that a logical problem has occurred and the fault domain is identified. Given its error detection and recovery mechanisms, FDDI is considered to be highly reliable and is widely employed as a backbone for local and campus area networks.

HiSpeed FDDI Uplink

LEDs Port B Port A

Optical Bypass

Connector

Figure 12-2. FDDI Uplink Module installed in an HS150

12-2 US7070447-001, Rev 01