Question: What format should the username part of a Root NAI comply with when using EAP AKA authentication, and how is the Root NAI constructed when it includes an IMSI for this authentication method?
Option 1: Comply with IETF RFC 4187; Constructed as "0<IMSI>@wlan.mnc<MNC>.mcc<MCC>.3gppnetwork.org" (e.g., "0234150999999999@wlan.mnc015.mcc234.3gppnetwork.org" for IMSI 234150999999999)
Option 2: Comply with IETF RFC 4186; Constructed as "1<IMSI>@wlan.mnc<MNC>.mcc<MCC>.3gppnetwork.org"
Option 3: Comply with IETF RFC 4282 only; No specific construction format mentioned for IMSI inclusion
Option 4: Comply with a custom format defined by 3GPP TS 23.003; Constructed without the "0" or "1" prefix (e.g., "234150999999999@wlan.mnc015.mcc234.3gppnetwork.org")
Explanation: For EAP AKA authentication, the username part of the Root NAI must comply with IETF RFC 4187. When the IMSI is included in the username, the Root NAI is specifically formatted to start with "0", followed by the IMSI, and then the domain constructed from the MNC and MCC (e.g., "@wlan.mnc<MNC>.mcc<MCC>.3gppnetwork.org"). This precise format ensures interoperability and correct identification in wireless networks.