Section: 28.12 NF Set Identifier (NF Set ID)
Content: A NF Set Identifier is a globally unique identifier of a set of equivalent and interchangeable CP NFs from a given network that provide distribution, redundancy and scalability (see clause 5.21.3 of 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [119]). An NF Set Identifier shall be constructed from the MCC, MNC, NID (for SNPN), NF type and a Set ID. A NF Set Identifier shall be formatted as the following string: set<Set ID>.<nftype>set.5gc.mnc<MNC>.mcc<MCC> for a NF Set in a PLMN, or set<Set ID>.<nftype>set.5gc.nid<NID>.mnc<MNC>.mcc<MCC> for a NF Set in a SNPN. where: - the <MCC> and <MNC> shall identify the PLMN of the NF Set and shall be encoded as follows: - <MCC> = 3 digits - <MNC> = 3 digits If there are only 2 significant digits in the MNC, one "0" digit shall be inserted at the left side to fill the 3 digits coding of MNC. - the Network Identifier (NID) shall be encoded as hexadecimal digits as specified in clause 12.7. - the <NFType> shall identify the NF type of the NFs within the NF set and shall be encoded as a value of Table 6.1.6.3.3-1 of 3GPP TS 29.510[ 5G System; Network function repository services; Stage 3 ]  [130] but with lower case characters; - the Set ID shall be a NF type specific Set ID within the PLMN, chosen by the operator, that shall consist of alphabetic characters (A-Z and a-z), digits (0-9) and/or the hyphen (-) and that shall end with either an alphabetic character or a digit; - the case of alphabetic characters is not significant (i.e. two NF Set IDs with the same characters but using different lower and upper cases identify the same NF Set). For an AMF set, the Set ID shall be set to "<AMF Set ID>-region<AMF Region ID>", with the AMF Region ID and AMF Set ID encoded as defined in 3GPP TS 29.571[ 5G System; Common Data Types for Service Based Interfaces; Stage 3 ]  [129]. EXAMPLE 1: setxyz.smfset.5gc.mnc012.mcc345 EXAMPLE 2: set12.pcfset.5gc.mnc012.mcc345 EXAMPLE 3: set001-region48.amfset.5gc.mnc012.mcc345 (for AMF Region 48 (hexadecimal) and AMF Set 1) EXAMPLE 4: setxyz.smfset.5gc.nid000007ed9d5.mnc012.mcc345 for a SNPN with the NID 000007ed9d5 (hexadecimal). NOTE 1: If needed, an FQDN can be derived from a given NF Set ID by appending the ".3gppnetwork.org" domain to the NF Set ID, see e.g. SMF Set FQDN in clause 28.3.2.9. For NFs whose NF type contains an underscore and for which an FQDN needs to be derived, the underscore is replaced by an hyphen in the corresponding label of the FQDN. As an exception, the AMF Set FQDN defined in clause 28.3.2.7 is not derived by merely appending the ".3gppnetwork.org" domain to the NF Set ID of an AMF set defined in this clause. NF Instances of an NF Set are equivalent and share the same MCC, MNC, NID (for SNPN), NF type and NF Set ID. In earlier versions of this specification, the Set ID of an AMF Set was defined to be set to the string "<AMF Set ID>.region<AMF Region ID>". For backward compatibility with AMF implementations complying with these earlier versions of the specifications, AMF peers' implementations shall: - support receiving such a former encoding of an AMF Set ID in 3GPP custom HTTP headers (e.g. 3gpp-Sbi-Binding header or 3gpp-Sbi-Producer header) and shall interpret it the same as if they receive these headers with the AMF Set format defined in the current version of the specification; and - use the amf-region-id and the amf-set-id query parameters when they need to discover the AMF profiles of the AMF set registered at the NRF, when receiving a binding header with such a former encoding of the AMF Set ID. NOTE 2: The NF Set ID format for an AMF set defined in earlier versions of the specification cannot be encoded in JSON attributes defined with the NfSetId data type of 3GPP TS 29.571[ 5G System; Common Data Types for Service Based Interfaces; Stage 3 ]  [129] which does not allow to encode a period ".". Accordingly, any such attribute encodes the Set ID of an AMF set as defined above (i.e. <AMF Set ID>-region<AMF Region ID>").