Question: What action does the ng-eNB take after receiving an N2 Resume Response message from the AMF that includes a new {NH, NCC} pair?
Option 1: The ng-eNB ignores the new {NH, NCC} pair and continues to use the existing one.
Option 2: The ng-eNB stores the new {NH, NCC} pair and removes any existing unused stored pairs.
Option 3: The ng-eNB sends an error message to the AMF indicating that it cannot accept the new {NH, NCC} pair.
Option 4: The ng-eNB uses the new {NH, NCC} pair immediately for all future suspend/resume or Xn handover procedures.
Explanation: According to the security architecture and procedures for 5G System, when the ng-eNB receives an N2 Resume Response message from the AMF that includes a new {NH, NCC} pair, it stores the new pair and removes any existing unused stored pairs. This ensures that the ng-eNB has the most up-to-date security information for future suspend/resume or Xn handover procedures.