Question: During an X2 handover in a 3GPP SAE network, what is the primary purpose of the MME sending a new {NH, NCC} pair to the target eNB in the S1 PATH SWITCH REQUEST ACKNOWLEDGE message?
Option 1: To immediately update the encryption keys for the ongoing session with the UE.
Option 2: To provide keying material for potential future handovers from the target eNB.
Option 3: To authenticate the target eNB for the handover procedure.
Option 4: To notify the target eNB of a change in the UE's subscription profile.
Explanation: The correct answer is Option 2 because the path switch message (and thus the new {NH, NCC} pair) is transmitted after the radio link handover. This timing means it can only be used to provide keying material for the next handover procedure from the target eNB, not for the current handover, ensuring key separation after two hops.