A value that identifies a set of RTT data. The value of this
object is influenced by the etsysIpSlaCollectionType.
If the collection type is 'summary', the value of this object is
one. There is only one RTT summary per data collection.
If the collection type is 'distribution' the value of this
object represents the distribution index. There is an
associated entry in the etsysIpSlaDistDataTable.
If the collection type is 'history', the value of this object
is in the range of one to etsysIpSlaConfigHistoryBuckets.