Question: What is the primary impact of the LENGTH parameter on the keystream block generation in 3GPP cryptographic algorithms for a single physical layer frame?
Option 1: It determines both the length and the actual bits of the keystream block.
Option 2: It affects only the length of the keystream block, not altering its actual bits.
Option 3: It sets a fixed maximum size for RLC PDU / MAC SDU across all bearers and transmission directions.
Option 4: It dictates the minimum number of RLC PDUs / MAC SDUs sent in a single physical layer frame.
Explanation: According to 3GPP cryptographic algorithm requirements, the LENGTH parameter influences the variable length of the keystream block generated for a given bearer and transmission direction, without altering the actual bits within the keystream. This ensures flexibility in accommodating varying plaintext block sizes during single physical layer frame transmissions.