Section: 19.3.2 Root NAI
Content: The Root NAI shall take the form of an NAI, and shall have the form username@realm as specified in clause 2.1 of IETF RFC 4282 [53]. When the username part is the IMSI, the realm part of Root NAI shall be built according to the following steps: 1. Convert the leading digits of the IMSI, i.e. MNC and MCC, into a domain name, as described in clause 19.2. 2. Prefix domain name with the label of "nai". The resulting realm part of the Root NAI will be in the form: "@nai.epc.mnc<MNC>.mcc<MCC>.3gppnetwork.org" When including the IMSI, the Root NAI is prepended with a specific leading digit when used for EAP authentication (see 3GPP TS 29.273[ Evolved Packet System (EPS); 3GPP EPS AAA interfaces ]  [78]) in order to differentiate between EAP authentication method. The leading digit is: - "0" when used in EAP-AKA, as specified in IETF RFC 4187 [50] - "6" when used in EAP-AKA', as specified in IETF RFC 5448 [82]. The resulting Root NAI will be in the form: "0<IMSI>@nai.epc.mnc<MNC>.mcc<MCC>.3gppnetwork.org" when used for EAP AKA authentication "6<IMSI>@nai.epc.mnc<MNC>.mcc<MCC>.3gppnetwork.org" when used for EAP AKA' authentication For example, if the IMSI is 234150999999999 (MCC = 234, MNC = 15), the Root NAI takes the form 0234150999999999@nai.epc.mnc015.mcc234.3gppnetwork.org for EAP AKA authentication and the Root NAI takes the form 6234150999999999@nai.epc.mnc015.mcc234.3gppnetwork.org for EAP AKA' authentication. The NAI sent in the Mobile Node Identifier field in PMIPv6 shall not include the digit prepended in front of the IMSI based username that is described above.