R-APS Instance Ring Port Table. Each entry in this table defines a port belonging to a R-APS instance. Only applicable when main ring's control protocol is raps (prvtRapsInstControlProtocol equals 'raps'). Exactly two interfaces must be defined per instance. This includes physical ports (defined in prvtRapsInstRingPortTable) and LAG interfaces (defined in prvtRapsInstRingLagTable). In the case when one physical port and one LAG interface is used, the two port index values must be unique (i.e. prvtRapsInstRingPortIndex must not equal prvtRapsInstRingLagIndex)