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DES-7200 Configuration Guide Chapter 5 RERP Configuration
5-5
Figure-3
As shown in Figure-3, two rings are intersected in Region 1. In other words, the two
rings (main-ring and sub-ring) share one link. The two intersected nodes are called
Primary-edge and Secondary-edge respectively. RERP only support one sub-ring in
one shared link. The connection line between Secondary-edge and Primary-edge in
Figure-3 is the shared link. The characteristic of the intersected rings is that the RERP
messages for the sub-ring can be controlled as the datagram in the main-ring that
provides two backup links for the sub-ring. As shown in the Figure, the
Secondary-edge and Primary-edge communicate through two paths. If one path is
Down, no change happens for the sub-ring. While if the two paths are both Down,
Secondary-edge is able to detect the failure rapidly and notify the Master in the
sub-ring in time, enabling the rapid switchover of the sub-ring, rather than switchover
untill the hello failure for the sub-ring. Besides, when the link between the
Secondary-edge and the Primary-edge is recovered, Secondary-edge will discover
and notify the Master in the sub-ring of blocking the secondary port and loop
prevention. That fast processing depends on the new edge health detection
mechanism between the Secondary-edge and the Primary-edge. The Secondary-edge
and Primary-edge inter-detect each other in both directions of the main-ring, and the
Secondary-edge is responsible for notifying the Master in the sub-ring. This ring