Question: What is the primary consideration for an MME to allocate a periodic RAU/TAU timer value to a UE during Attach and TAU procedures?
Option 1: The subscribed periodic RAU/TAU timer value received from the HSS, if available.
Option 2: The VPLMN operator policy, regardless of other factors.
Option 3: The low access priority indication from the UE, if present.
Option 4: The Start of Unavailability Period and/or Unavailability Period Duration, if using a RAN that provides discontinuous coverage.
Explanation: According to the text, if an MME receives a subscribed periodic RAU/TAU timer value from the HSS, it allocates this value to the UE as the periodic TAU timer. This indicates that the subscribed value takes precedence over other factors in determining the allocated timer value.