This index is used as a secondary index to uniquely identify this row. Before creating a row in this table, the 'mplsLdpEntityIndexNext' object should be retrieved. That value should be used for the value of this index when creating a row in this table. NOTE: if a value of zero (0) is retrieved, that indicates that no rows can be created in this table at this time. A secondary index (this object) is meaningful to some but not all, LDP implementations. For example an LDP implementation which uses PPP would use this index to differentiate PPP sub-links. Another way to use this index is to give this the value of ifIndex. However, this is dependant on the implementation.