This reports whether the associated tunnel is currently in standby or active protection state, telling the admin which of a primary/backup pair is presently carrying live traffic regardless of which one is nominally the primary by role. Since role and state are tracked separately, an admin cross-references both to detect a failover that hasn't yet reverted, which would show primary role paired with standby state. For example, a tunnel with protection role primary but protection state standby(0) confirms the network has already failed over to its backup and traffic engineers should check why the primary hasn't been restored.