This object contains an appropriate value to be used
for mplsXCIndex when creating entries in the
mplsXCTable. The value 0 indicates that no
unassigned entries are available. To obtain the
value of mplsXCIndex for a new entry in the
mplsXCTable, the manager issues a management
protocol retrieval operation to obtain the current
value of mplsXCIndex. After each retrieval
operation, the agent should modify the value to
reflect the next unassigned index. After a manager
retrieves a value the agent will determine through
its local policy when this index value will be made
available for reuse.