The value of tmnxEthRingSubRingType specifies whether this Ethernet
Ring is a sub-ring or not. A value of 'none (0)' specifies that the
Ethernet Ring is not a sub-ring. A value 'virtualLink (1)' specifies
that the Ethernet Ring is a sub-ring with R-APS virtual channel, while
the value 'nonVirtualLink (2)' specifies that the Ethernet Ring is a
sub-ring without R-APS virtual channel.
This object MUST be set to a value other than 'none (0)' for
tmnxEthRingSubRingInterconnectId and tmnxEthRingSubRingPropTopChange to
be modified away from their default values.