This is the inverse ifstacktable in that the index scheme is lower.higher as opposed to higher.lower as defined in rfc2233. Comments and information is copied here for clarity. Information on a particular relationship between two sub-layers, specifying that one sub-layer runs on 'top' of the other sub-layer. Each sub-layer corresponds to a conceptual row in the ifTable. Use of this table is solely for management stations to walk the table (getnext) from the lower physical port (ifindex) up the stack.