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62 SunFDDI/P 1.0 Adapter User’s Guide—May1997
6
Figure 6-10 Dual-Attached Station in Wrap Mode
Optical Bypass Switches
Station wrapping provides effective network recovery in the event of a single
station or cable failure. However, two or more failures in the ring will isolate
portions of the network, as shown in Figure 6-11.
This limitation can be overcome to a certain extent by fitting optical bypass
switches to the dual-attached stations. As their name suggests, these switches
provide an optical connection that bypasses the station in the event of failure,
or if the station needs to be removed from the ring. Optical bypass switches
can only be used to overcome station faults; they have no affect in the event of
a cable fault.
The attenuation in an optical bypass switch is far greater than in a normal
FDDI connection; therefore, the number of optical bypass switches that can be
connected in series in a single ring is limited.
Dual-attached station
(DAS)
Pout
Data to downstream station
MAC
PHY B
PHY A
Sin
Data from upstream station
port B
port A
Primary and secondary rings
wrapped within the MAC l