This is a three-dimensional table whose entries are indices into the assocTable. For each MTA in the applTable, there is a two-dimensional sub-table. This two-dimensional sub-table has a row for each channel in the corresponding MTA. For each channel, there is an entry for each active network connection which that channel has currently underway. The value of the entry is the index into the assocTable (as indexed by the entry’s value and the applIndex index of the MTA being looked at). This indicated entry in the assocTable is a network connection held by the channel.
In simple terms, the mtaGroupAssociationTable table correlates the network connections shown in the assocTable with the responsible channels in the mtaGroupTable.
Below is an example of data from mtaGroupAssociationTable (mib-188.8.131.52).
mtaGroupAssociationTable: mtaGroupAssociationIndex.1.3.1 = 1 1 mtaGroupAssociationIndex.1.3.2 = 2 mtaGroupAssociationIndex.1.3.3 = 3 mtaGroupAssociationIndex.1.3.4 = 4 mtaGroupAssociationIndex.1.3.5 = 5 mtaGroupAssociationIndex.1.3.6 = 6 mtaGroupAssociationIndex.1.3.7 = 7
In the .x.y.z suffix, x is the application index, applIndex, and indicates which application in the applTable is being reported on. In this case, the MTA. The y indicates which channel of the mtaGroupTable is being reported on. In this example, 3 indicates the tcp_local channel. The z serves to enumerate the associations open to or from the channel.
The value here is an index into the assocTable. Specifically, x and this value become, respectively, the values of the applIndex and assocIndex indices into the assocTable. Or, put differently, this is saying that (ignoring the applIndex) the first row of the assocTable describes a network connection controlled by the tcp_local channel.