This read-only object identifies which entry in the vsiSessionTable, and thus which VSI session, controls a given logical interface, since every logical interface belongs to the domain of a particular VSI slave communicating through one session. An administrator uses this to trace a logical interface back to the specific master-slave session responsible for managing it, useful when a session drops and its interfaces need to be identified. For example, if a VSI session fails, the admin can find all affected logical interfaces by matching vsiLogicalIfSessionIndex to that session's index.