Question: Upon receiving a message with a 'Procedure Code IE' marked as 'Ignore IE and Notify Sender' that is not comprehended by the UTRAN Iu interface's RANAP, how should the receiving node respond?
Option 1: The receiving node shall reject the procedure using the Error Indication procedure without notifying the sender.
Option 2: The receiving node shall ignore the procedure and initiate the Error Indication procedure to notify the sender.
Option 3: The receiving node shall acknowledge the procedure but not execute it, without initiating any error procedures.
Option 4: The receiving node shall terminate the connection to prevent further incomprehensible messages.
Explanation: According to the specified behavior for 'Ignore IE and Notify Sender' criticality, when a receiving node encounters an incomprehensible Procedure Code IE marked as such, it is mandated to ignore the procedure itself but also to notify the sender of the issue. This is achieved by initiating the Error Indication procedure, which serves as the mechanism for notification in this context.