Question: In UTRAN Iu interface (RANAP signalling), what triggers the Source RNC to initiate an Iu Release Request towards the Core Network (CN) with a cause value of "TRELOCoverall expiry"?
Option 1: Expiry of timer T302, indicating a failure in the relocation preparation phase.
Option 2: Failure of the CN to initiate the Iu Release procedure before the expiry of timer TRELOCoverall.
Option 3: Successful completion of the handover procedure, requiring resource release.
Option 4: Receipt of a UE (User Equipment) detach request from the Core Network.
Explanation: This is correct because, according to the specified behavior for abnormal conditions in RANAP signalling, if the CN does not start the Iu Release procedure before the TRELOCoverall timer expires, the Source RNC takes initiative. This ensures resources are released timely even if the expected signal from the CN is delayed or missing, maintaining network efficiency and resource availability.