Question: What is the primary purpose of the 'notification of a transmission opportunity' service expected by the Radio Link Control (RLC) protocol from the lower layer (Media Access Control, MAC)?
Option 1: To inform RLC about the available buffer size for incoming data
Option 2: To notify RLC of the total size of the RLC PDU(s) that can be transmitted in a given transmission opportunity
Option 3: To request RLC to prioritize data transfer for specific UE (User Equipment)
Option 4: To indicate the current MAC layer's processing delay
Explanation: This service is crucial for efficient data transfer. By knowing the total size of the RLC PDU(s) that can be transmitted in a given transmission opportunity, RLC can optimize packet assembly and minimize potential fragmentation or padding, ensuring effective use of radio resources. This directly impacts the performance and capacity of the wireless network.