Question: What happens to a signalling request message if no response is received before the T3-RESPONSE timer expires and the total number of request attempts is less than N3-REQUESTS times?
Option 1: The request is discarded, and an error message is sent to the upper layer.
Option 2: The request is retransmitted, and the T3-RESPONSE timer is restarted.
Option 3: The path list is cleared, and a new Sequence Number is generated for the next request.
Option 4: A duplicate response message is generated to acknowledge the original request.
Explanation: According to the reliable delivery mechanism for signalling messages, if a response to a signalling request message is not received before the T3-RESPONSE timer expires, and the maximum number of retransmissions (N3-REQUESTS) has not been reached, the request message is retransmitted. This ensures that the message is delivered reliably, minimizing loss in transmission. The T3-RESPONSE timer is typically restarted after each retransmission to allow for additional time to receive a response.