LTE: How an UE come to know whether it has to perform periodic TAU or not ?

Question

There are two ways for tracking area update procedure to get triggered from UE to network . One is known as periodic and other one as non-periodic.

Answer 1

During the attach procedure, MME sets the value of Timer T3412 . If MME sets this timer value to "0" then it means network is not expecting periodic TAU request from the UE . It would be event based. In Idle mode, when UE enters into a cell whose tracking area is different from the list of TAI list sent by the MME during the attach procedure , TAU procedure is executed by UE.
Network prefers T3412 timer value as"0" for the M2M devices as per my knowledge.
If someone knows reason other than what I mentioned here then please add.