Question: What is the purpose of the Alternative-APN AVP (AVP code 905) in the Gmb interface?
Option 1: To indicate the UE's preferred APN for the MBMS PDP Context.
Option 2: To inform the BM-SC to use a different APN for the MBMS PDP Context than the one used in the Join message.
Option 3: To specify the default APN for all UEs in the network.
Option 4: To request the UE to use a specific APN for non-MBMS services.
Explanation: The Alternative-APN AVP is used by the BM-SC to indicate that the UE must use a different APN for the MBMS PDP Context than the one used in the Join message. This allows the network to dynamically change the APN used for MBMS services, if necessary.