Question: What distinguishes the format of a Full Authentication Network Access Identifier (NAI) for EAP-AKA from that of EAP-SIM, in terms of the prefix and realm structure, as per telecom standards?
Option 1: The presence or absence of the "gan" prefix in the realm, with EAP-AKA including it and EAP-SIM omitting it.
Option 2: The leading digit in the NAI; EAP-AKA authentication starts with "0" followed by the IMSI, while EAP-SIM authentication starts with "1" followed by the IMSI.
Option 3: The order of Mobile Country Code (MCC) and Mobile Network Code (MNC) in the realm, which is reversed between EAP-AKA and EAP-SIM.
Option 4: The top-level domain, with EAP-AKA using ".3gppnetwork.org" and EAP-SIM using a different domain.
Explanation: The correct distinction lies in the leading digit of the NAI, which is used to differentiate between EAP-AKA and EAP-SIM authentications. This digit, "0" for EAP-AKA and "1" for EAP-SIM, precedes the IMSI in the Full Authentication NAI format. This unique prefix ensures clear identification of the authentication type within the telecom network, facilitating proper handling of authentication requests.