Question: How does an MME differentiate between a GUMMEI mapped from P-TMSI/RAI and a native GUMMEI in PLMNs deployed with the mechanism described?
Option 1: Based on the value of the least significant bit of the MME Group ID.
Option 2: Based on the value of the most significant bit of the LAC.
Option 3: Based on the presence or absence of a specific flag in the GUTI.
Option 4: Based on the value of the most significant bit of the MME Group ID, where "0" indicates a mapped GUMMEI and "1" indicates a native GUMMEI.
Explanation: According to the specification, an MME differentiates between a GUMMEI mapped from P-TMSI/RAI and a native GUMMEI based on the value of the most significant bit (MSB) of the MME Group ID. If the MSB is set to "0", the GUMMEI is mapped from P-TMSI/RAI, and if the MSB is set to "1", the GUMMEI is a native one. This allows the MME to correctly identify the type of GUMMEI being used in the network.