Question: In RANAP signalling (UTRAN Iu interface), when a receiving node supports a procedure but cannot perform requested functionality marked as "shall" be executed under a certain condition in a Class 1 or Class 3 Elementary Procedure (EP), how shall the receiving node respond?
Option 1: Ignore the request and continue with ongoing procedures.
Option 2: Respond with a success message, assuming an alternative action.
Option 3: Proceed with the execution of the EP without the requested functionality.
Option 4: Respond with a message reporting an unsuccessful outcome, containing an appropriate cause value.
Explanation: According to the specified procedure logic principles for RANAP signalling, if a receiving node supports a procedure (e.g., Class 1 or Class 3 EP) but cannot execute a "shall" functionality as requested, it must respond with a message indicating an unsuccessful outcome. This response includes a cause value explaining why the action could not be performed, ensuring transparency and facilitating appropriate action by the requesting node in UTRAN's Radio Access Network.