Question: What action does a receiving node take when a response message initiating a procedure is missing one or more Information Elements (IEs)/IE groups with specified criticality 'Ignore IE and Notify Sender' in UTRAN Iu-BC interface using SABP?
Option 1: Reject the procedure and report the missing IEs/IE groups using the Error Indication procedure.
Option 2: Terminate the procedure without further action, as the criticality is set to ignore.
Option 3: Ignore the missing IEs/IE groups, continue with the procedure based on present IEs/IE groups, and initiate the Error Indication procedure to report the missing IEs/IE groups.
Option 4: Request retransmission of the entire message before proceeding.
Explanation: According to the specified behavior for 'Ignore IE and Notify Sender' criticality in response messages, the receiving node should ignore the missing elements, proceed with the available information, and notify the sender about the missing IEs/IE groups through the Error Indication procedure. This ensures the procedure continues while still acknowledging and reporting the discrepancy.