Description: There are four RRPP node modes for the switch on a RRPP ring, such as master, transit, edge and assistant-edge. Each RRPP ring has a single designated master-node. All other nodes except edge-node and assistant-edge-node on that ring are referred to as transit-nodes. The node mode of edge and assistant-edge should be configured only on sub-ring. When there is a common link between a sub-ring and its major-ring, the node mode of the sub-ring must be edge or assistant-edge, and they must be configured in pairs. If node mode is designated as edge or assistant-edge, several points should be noticed: Major-ring must be created before a sub-ring is created; Major-ring can't be deleted unless all its sub-rings are deleted; The node mode of the switch on major-ring must be transit; Major-ring and sub-ring must have only a common port. This value can't be modified after created.