Although Station 3 is no longer on the ring, network operation continues for the remaining stations. Ring Recovery Configuration Figure 9-5 shows how FDDI compensates for a wiring failure. Stations 3 and 4 wrap the ring within themselves when wiring between them fails. As FDDI networks grow, the possibility of multiple ring failures grows. When two ring failures occur, the ring will be wrapped in both cases, effectively segmenting the ring into two separate rings that cannot communicate with each other.
Subsequent failures cause additional ring segmentation.
Optical bypass switches can be used to prevent ring segmentation by eliminating failed stations from the ring. This is shown in Figure 9-6 . In dual-homing situations, the critical device is attached to two concentrators. When this occurs, the passive link is automatically activated. It consists of signaling patterns that differentiate it from the rest of the frame.