A conceptual row in the protocolDistStatsTable.
The index is composed of the protocolDistControlIndex of the
associated protocolDistControlEntry, followed by the
protocolDirLocalIndex of the associated protocol that this
entry represents. In other words, the index identifies the
protocol distribution an entry is a part of and the
particular protocol that it represents.
An example of the indexing of this entry is
protocolDistStatsPkts.1.18