Section: 28.3.2.2.6 FQDN for SNPN N3IWF
Content: 28.3.2.2.6.1 SNPN Identifier based N3IWF FQDN and Visited Country FQDN for SNPN N3IWF The SNPN Identifier based N3IWF FQDN is used by a UE to access SNPN service in its subscribed SNPN via PLMN or directly via an untrusted non-3GPP access, as specified in clause 6.3.6.2a of 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [119]. The N3IWF FQDN is composed of seven labels. The last three labels shall be "pub.3gppnetwork.org". The third label and fourth labels together shall identify the SNPN (the country where it is located along with the SNPN ID). The first two labels shall be "n3iwf.5gc". Hence, the SNPN Identifier based N3IWF FQDN shall be constructed as follows: "n3iwf.5gc.snpnid<SNPNID>.mcc<MCC>.pub.3gppnetwork.org". The <MCC> coding used in this FQDN shall be: - <MCC> = 3 digits The <SNPNID> coding used in this FQDN shall be: - <SNPNID> = PLMN ID || NID where, PLMN ID = MCC || MNC NOTE 1: The MCC used in the SNPNID is not necessarily the same (e.g. it can be 999 reserved for internal use) as the one used in coding the <MCC>. NOTE 2: Locally assigned NIDs are not supported, since a DNS cannot be properly configured for multiple SNPNs using the same locally assigned NID. As an example, SNPN Identifier based N3IWF FQDN for MCC 098, SNPN MCC 999, MNC 305, and NID 456789ABCDE is coded in the DNS as: "n3iwf.5gc.snpnid999305456789ABCDE.mcc098.pub.3gppnetwork.org" The Visited Country FQDN for SNPN N3IWF, used by a UE in the visited country to determine whether the visited country mandates the selection of an N3IWF in this country for the SNPN identified by the SNPN Identifier provided by the UE, shall be constructed as described below. The Visited Country FQDN for SNPN N3IWF shall contain a MCC that uniquely identifies the country in which the UE is located, and the SNPN Identifier. The Visited Country FQDN for SNPN N3IWF is composed of eight labels. The last three labels shall be "pub.3gppnetwork.org". The fifth label shall be "visited-country". The fourth label shall uniquely identify the MCC of the visited country. The third label shall be the SNPN Identifier as specified in clause 12.7. The first and second labels shall be "n3iwf.5gc". The Visited Country FQDN for SNPN N3IWF shall be constructed as follows: "n3iwf.5gc.snpnid<SNPNID>.mcc<MCC>.visited-country.pub.3gppnetwork.org" The <MCC> coding used in this FQDN shall be: - <MCC> = 3 digits The <SNPNID> coding used in this FQDN shall be: - <SNPNID> = MCC || MNC || NID NOTE 1: The MCC used in the SNPNID is not necessarily the same (e.g. it can be 999 reserved for internal use) as the one used in coding the <MCC>. NOTE 2: Locally assigned NIDs are not supported, since a DNS cannot be properly configured for multiple SNPNs using the same locally assigned NID. As an example, the Visited Country FQDN for SNPN N3IWF for MCC 345, SNPN MCC 999, MNC 123, and NID 456789ABCDE is coded in the DNS as: "n3iwf.5gc.snpnid999123456789ABCDE.mcc345.visited-country.pub.3gppnetwork.org". NOTE 3: The identity (i.e. the corresponding DNS record) of an SNPN's N3IWF in the visited country can be any FQDN and is not required to include the SNPN identifier. 28.3.2.2.6.2 Visited Country FQDN for SNPN N3IWF supporting Onboarding SNPN N3IWF supporting Onboarding is specified in clause 5.30.2.12 of 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [119]. If an SNPN for onboarding has been selected, Visited Country FQDN for SNPN N3IWF indicates that the SNPN identified by the SNPN in the DNS response shall support onboarding. Visited Country FQDN for SNPN N3IWF supporting Onboarding is composed of eight labels. The last four labels shall be " visited-country.pub.3gppnetwork.org". The fourth label shall uniquely identify the MCC of the visited country. The second and third labels shall be "n3iwf.snpn-5gc". The first label shall be "onboarding". The resultant Visited Country FQDN for SNPN N3IWF supporting Onboarding shall be constructed as follows: "onboarding.n3iwf.snpn-5gc.mcc<MCC>.visited-country.pub.3gppnetwork.org" As an example, the Visited Country FQDN for SNPN N3IWF, which also supports Onboarding for MCC 345 is coded in the DNS as: "onboarding.n3iwf.snpn-5gc.mcc345.visited-country.pub.3gppnetwork.org". 28.3.2.2.6.3 Visited Country Emergency SNPN FQDN The Visited Country Emergency SNPN FQDN, used by a UE to determine whether the visited country mandates the selection of an SNPN N3IWF for emergency service in this country, shall be constructed as described below. The Visited Country Emergency SNPN FQDN shall contain a MCC that uniquely identifies the country in which the UE is located. The Visited Country Emergency SNPN FQDN is composed of eight labels. The last three labels shall be "pub.3gppnetwork.org". The fifth label shall be "visited-country". The forth label shall uniquely identify the MCC of the visited country. The second and third labels shall be "n3iwf.snpn-5gc". The first label shall be "sos"". The resulting Visited Country Emergency SNPN FQDN shall be constructed as follows: "sos.n3iwf.snpn-5gc.mcc<MCC>.visited-country.pub.3gppnetwork.org". As an example, the Visited Country Emergency SNPN FQDN for MCC 345 is coded in the DNS as: "sos.n3iwf.snpn-5gc.mcc345.visited-country.pub.3gppnetwork.org". 28.3.2.2.6.4 Replacement field used in DNS-based Discovery of regulatory requirements for emergency services in SNPN If the visited country mandates the selection of an SNPN N3IWF for emergency services in this country, the NAPTR record(s) associated to the Visited Country Emergency SNPN FQDN shall be provisioned with the replacement field containing the identity of the SNPN(s) in the visited country which may be used for N3IWF selection. The replacement field shall take the form of an SNPN Identifier based N3IWF FQDN as specified in clause 28.3.2.2.6.1 with the addition of the label "sos" before the labels "n3iwf.5gc" as "sos.n3iwf.5gc.snpnid<SNPNID>.mcc<MCC>.pub.3gppnetwork.org". As an example, the NAPTR records associated to the Visited Country Emergency SNPN FQDN for MCC 345, and for a) SNPN MCC 999, MNC 012, and NID 345678ABCDE; b) SNPN MCC 345, MNC 013, and NID 345678BCDEF; and c) SNPN MCC 999, MNC 014, and NID 234567CDEFG, are provisioned in the DNS as: sos.n3iwf.snpn-5gc.mcc345.visited-country.pub.3gppnetwork.org ; IN NAPTR order pref. flag service regexp replacement IN NAPTR 100 999 "" "" sos.n3iwf.5gc.snpnid999012345678ABCDE.mcc345.pub.3gppnetwork.org IN NAPTR 100 999 "" "" sos.n3iwf.5gc.snpnid345013345678BCDEF.mcc345.pub.3gppnetwork.org IN NAPTR 100 999 "" "" sos.n3iwf.5gc.snpnid999014234567CDEFG.mcc345.pub.3gppnetwork.org NOTE: The SNPN ID in the NAPTR records do not contain the NID using self-assignment model since a DNS cannot be properly configured for multiple SNPNs using the same self-assigned NID.