Content for  TS 23.003  Word version:  18.3.0

This clause describes the NAI formats used in the 5G System.

The NAI for SUPI shall have the form username@realm as specified in Section 2.2 of RFC 7542. A SUPI containing a network specific identifier shall take the form of a Network Access Identifier (NAI). See clause 5.9.2 of TS 23.501 for the definition and use of the network specific identifier. In SNPN scenarios, the realm part of the NAI may include MCC, MNC and the NID of the SNPN (see clauses 5.30.2.3, 5.30.2.9, 6.3.4, and 6.3.8 of TS 23.501 for the realm part format see Home Network Domain for an SNPN in clause 28.2). See clauses 28.15.2 and 28.16.2 for the NAI format for a SUPI containing a GCI or a GLI.

When the SUPI is defined as a Network Specific Identifier, the SUCI shall take the form of a Network Access Identifier (NAI). In this case, the NAI format of the SUCI shall have the form username@realm as specified in Section 2.2 of RFC 7542, where the realm part shall be identical to the realm part of the Network Specific Identifier. In SNPN scenarios, the realm part of the NAI may include MCC, MNC and the NID of the SNPN (see clauses 5.30.2.3, 5.30.2.9, 6.3.4, and 6.3.8 of TS 23.501 for the realm part format see Home Network Domain for an SNPN in clause 28.2). When the SUPI is defined as an IMSI, the SUCI in NAI format shall have the form username@realm, where the realm part shall be constructed by converting the leading digits of the IMSI, i.e. MNC and MCC, into a domain name, as described in clause 28.2. In SNPN scenarios, the realm part shall additionally include the NID of the SNPN, if available. The resulting realm part of the NAI shall be in the form: The username part of the NAI shall take one of the following forms:

1. for the null-scheme:
   type<supi type>.rid<routing indicator>.schid<protection scheme id>.userid<MSIN or Network Specific Identifier SUPI username>
2. for the Scheme Output for Elliptic Curve Integrated Encryption Scheme Profile A and Profile B:
   type<supi type>.rid<routing indicator>.schid<protection scheme id>.hnkey<home network public key id>.ecckey<ECC ephemeral public key value>.cip<ciphertext value>.mac<MAC tag value>
3. for HPLMN proprietary protection schemes:
   type<supi type>.rid<routing indicator>.schid<protection scheme id>.hnkey<home network public key id>. out<HPLMN defined scheme output>
   See clause 2.2B for the definition and format of the different fields of the SUCI.

EXAMPLES: See clauses 28.15.5 and 28.16.5 for the NAI format for a SUCI containing a GCI or a GLI.

This clause describes the format of the UE identification when UE is performing an emergency registration and IMSI is not available or not authenticated. The Emergency NAI for Limited Service State shall take the form of an NAI, and shall have the form username@realm as specified in Section 2.2 of RFC 7542. The exact format shall be:

• imei<IMEI>@sos.invalid

or if IMEI is not available,

• mac<MAC>@sos.invalid

For example, if the IMEI is 219551288888888, the Emergency NAI for Limited Service State then takes the form of imei219551288888888@sos.invalid. For example, if the MAC address is 44-45-53-54-00-AB, the Emergency NAI for Limited Service State then takes the form of mac4445535400AB@sos.invalid, where the MAC address is represented in hexadecimal format without separators.

The Alternative NAI shall take the form of a NAI, i.e. 'any_username@realm' as specified of RFC 7542. The Alternative NAI shall not be routable from any AAA server. The Alternative NAI shall contain a username part that is not a null string. The realm part of the NAI shall be "unreachable.3gppnetwork.org". The result shall be an NAI in the form of:

While performing the EAP-authentication procedure when a UE attempts to register to 5GCN via a trusted non-3GPP access network in a selected PLMN (see clause 4.12a of TS 23.502), the UE shall derive a NAI from the identity of the selected PLMN in the following format: where:

1. the username part <any_non_null_string> is any non null string; and
2. the <MNC> and <MCC> identify the PLMN (either HPLMN or VPLMN) to which the UE attempts to connect via the trusted non-3GPP access network as described in clause 6.3.12 of TS 23.501.

While performing the EAP-authentication procedure when a UE attempts to register to 5GCN via a trusted non-3GPP access network in a selected SNPN (see clause 5.30.2.13 of TS 23.501), the UE shall derive a NAI from the identity of the selected SNPN in the following format: where:

1. the username part <any_non_null_string> is any non null string; and
2. the <MNC>, <MCC> and <NID> identify the SNPN to which the UE attempts to connect via the trusted non-3GPP access network.

While performing the EAP authentication procedure when a UE attempts to register to 5GCN via a trusted non-3GPP access network in a selected TNGF, the UE shall derive NAI from the identity of the selected TNGF in the following format: "<any_non_mull_string>@tngfid<TNGF ID>.nai.5gc.mnc<MNC>.mcc<MCC>.3gppnetwork.org"; where:

1. The username part <any_non_mull_string> is any non null string; and
2. The <MNC> and <MCC> identify the PLMN (either HPLMN or VPLMN) to which the UE attempts to connect via the trusted non-3GPP access network; and
3. <TNGF ID> identifies the TNGF.

While performing the EAP-authentication procedure when a UE attempts to register to 5GCN via a trusted non-3GPP access network in a selected SNPN and TNGF, the UE shall derive a NAI from the identity of the selected SNPN and TNGF in the following format: "<any_non_null_string>@tngfid<TNGF ID>.nai.5gc.nid<NID>.mnc<MNC>.mcc<MCC>.3gppnetwork.org"; where:

1. the username part <any_non_null_string> is any non null string; and
2. the <MNC>, <MCC> and <NID> identify the SNPN to which the UE attempts to connect via the trusted non-3GPP access network; and
3. <TNGF ID> identifies the TNGF.

The NAI format of the 5G-GUTI shall have the form username@realm as specified in Section 2.2 of RFC 7542. The username part of the NAI shall take the following form: <5G-TMSI>, <AMF Pointer>, <AMF Set Id> and <AMF Region Id> are the hexadecimal strings of the 5G-TMSI, AMF Pointer, AMF Set ID and AMF Region ID. If there are less than 8 significant digits in <5G-TMSI>, "0" digit(s) shall be inserted at the left side to fill the 8 digits coding. If there are less than 2 significant digits in <AMF Pointer> or <AMF Region Id>, "0" digit(s) shall be inserted at the left side to fill the 2 digits coding of the AMF Pointer or AMF Region Id respectively. If there are less than 3 significant digits in <AMF Set Id>, "0" digit(s) shall be inserted at the left side to fill the 3 digits coding. Example: The NAI for an N5CW device in a PLMN (either HPLMN or VPLMN) with MNC=012 and MCC=345, to which the N5CW device attempts to connect via the trusted non-3GPP access, according to clause 28.7.7 is:

"tmsi06666666.­pt12.­set001.­region48@nai.­5gc-nn.­mnc012.­mcc345.­3gppnetwork.­org"

The NAI format for UP-PRUK ID shall have the form username@realm as specified in Section 2.2 of RFC 7542, where:

• the realm part shall be in the form:
  "prose-up.5gc.mnc<MNC>.mcc<MCC>.3gppnetwork.org"
• the username part shall be a non-empty string which is unique in the realm, as specified in TS 33.503.

The maximum length of a UP-PRUK ID in NAI format is 254 octets.

The NAI format for CP-PRUK ID shall have the form username@realm as specified in Section 2.2 of RFC 7542. The realm part shall be in the form: The username part of the NAI shall take one of the following forms: "rid<routing indicator>.pid<CP-PRUK ID*>"

• the <routing indicator> part is the "Routing Indicator" as specified in clause 2.2B.
• the <CP-PRUK ID*> part is the hexadecimal representation of the CP-PRUK ID* specified in clause A.2 of TS 33.503.

The maximum length of a CP-PRUK ID in NAI format is 254 octets.

When the UE decides to use 5G NSWO to connect to the WLAN access network using its 5GS credentials but without registration to 5GS, the NAI format for 5G NSWO in non-roaming scenarios is used. See clause 28.7.9.2 for the NAI format for 5G NSWO in roaming scenarios. In the 5G NSWO use case, the UE shall use a NAI in the following format:

• For PLMNs:
  "<username>@5gc-nswo.mnc<MNC>.mcc<MCC>.3gppnetwork.org"
• For SNPNs:
  "<username>@5gc-nswo.nid<NID>.mnc<MNC>.mcc<MCC>.3gppnetwork.org"

In the above use cases:

1. the username part is defined in clause 28.7.3; and
2. the label '5gc-nswo' in the realm part indicates that the NAI is used for 5G NSWO. For PLMNs, <MNC> and <MCC> identify the PLMN, and for SNPNs, <NID>, <MNC> and <MCC> identify the SNPN, to which the UE attempts to connect via the 5G NSWO as described in clause 4.2.15 of TS 23.501.