A conceptual row in the protocolDirTable.
An example of the indexing of this entry is
protocolDirLocalIndex.8.0.0.0.1.0.0.8.0.2.0.0, which is the
encoding of a length of 8, followed by 8 subids encoding the
protocolDirID of 1.2048, followed by a length of 2 and the
2 subids encoding zero-valued parameters.
Note that some combinations of index values may result in an
index that exceeds 128 sub-identifiers in length, which exceeds
the maximum for the SNMP protocol. Implementations should take
care to avoid such combinations.