Section: 19.3.9 IMSI-based Emergency NAI
Content: This clause describes the format of the UE identification needed to access the 3GPP EPC from non-3GPP accesses, when UE is performing an emergency attach and IMSI is available. For more information, see clause 4.4.1 of 3GPP TS 24.302[ Access to the 3GPP Evolved Packet Core (EPC) via non-3GPP access networks; Stage 3 ]  [77]. The IMSI-based Emergency NAI shall take the form of an NAI and shall be encoded as the Root NAI as specified in clause 19.3.2, but with the realm name prepended by the "sos" label. The resulting realm part of the IMSI-based Emergency NAI will be in the form: "@sos.nai.epc.mnc<MNC>.mcc<MCC>.3gppnetwork.org" The resulting IMSI-based Emergency NAI will be in the form: "0<IMSI>@sos.nai.epc.mnc<MNC>.mcc<MCC>.3gppnetwork.org" when used for EAP AKA authentication "6<IMSI>@sos.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 IMSI-based Emergency NAI takes the form 0234150999999999@sos.nai.epc.mnc015.mcc234.3gppnetwork.org for EAP AKA authentication and it takes the form 6234150999999999@sos.nai.epc.mnc015.mcc234.3gppnetwork.org for EAP AKA' authentication.