9000

Chapter 3 51

Installing the HP HSC FDDI/9000 Adapter

Connecting the Adapter to the Network

Figure 3-7 Typical Dual Ring with DAS Adapters

During normal operation of a dual ring with no faults, each station

receives and transmits all trafﬁc on the primary ring, while the

secondary ring is idle. If a station is turned off or disconnected from the

ring, neighboring stations detect this as a fault or discontinuity, and

wrap the trafﬁc onto the secondary ring, thus keeping remaining stations

in communication. However, if a second fault occurs during this time, the

ring could become segmented, separating groups of stations into

independent rings. An Optical Bypass Switch (OBS) can be used to

bypass a station that is turned off or disconnected, protecting against

multiple faults on a dual ring. Figure 3-8 shows the connection of the

OBS to a dual ring.

PHY A

PHY B

PHY A

PHY B

PHY A

PHY B