Question: In GERAN Iu-mode for CS domain, what action is taken by the BSC if it cannot provide an appropriate RAB corresponding to the GERAN BSC Container IE received in the RAB ASSIGNMENT REQUEST message?
Option 1: The BSC sends a RAB ASSIGNMENT RESPONSE with a cause value 'GERAN Iu-mode Failure' and includes the GERAN Classmark IE.
Option 2: The BSC ignores the GERAN BSC Container IE and attempts to establish a default RAB.
Option 3: The BSC requests additional information from the CS domain via a new RAB ASSIGNMENT REQUEST.
Option 4: The BSC aborts the RAB Assignment procedure without sending a response.
Explanation: This is the correct action for GERAN Iu-mode in the context of RAB Assignment procedures. When the BSC cannot fulfill the RAB request, it reports back with a 'GERAN Iu-mode Failure' cause and includes the GERAN Classmark IE for transparent and efficient error handling.