Each conceptual row represents a Layer Two Tunneling Protocol
Session.
Entries in this table are created and destroyed by the system.
In release 9.0 and higher, this information
is in the SUBSCRIBER-MGMT-MIB::tmnxSubPppTable.
The corresponding row in that table can be directly retrieved using
the value of the object tmnxL2tpLnsSePppSubPppIndex.