How it Works
The SMF uses priority attribute that is added in the smfInfo data type to enable the discovery and selection of SMF. This functionality is based on the relative priorities registered by the target SMFs in different smfInfo entries with different TAI lists.
The following table lists the feature-specific attributes that are part of NFProfile and SMFInfo data types.
smfInfo |
SmfInfo |
O |
0..1 |
Specific data for the SMF (DNNs). |
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smfInfoList |
map(SmfInfo) |
O |
1..N |
Multiple entries of SmfInfo. This attribute provides additional information to the smfInfo. smfInfoList may be present even if the smfInfo is absent. The key of the map will be a (unique) valid JSON string per clause 7 of IETF RFC 8259, with a maximum of 32 characters. |
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Attribute Name |
Data Type |
P |
Cardinality |
Description |
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sNssaiSmfInfoList |
array(sNssaiSmfInfoItem) |
M |
1..N |
List of parameters supported by the SMF per S-NSSAI. |
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taiList |
array(Tai) |
O |
1..N |
The list of TAIs the SMF can serve. It contains the non-3GPP access TAI. The absence of this attribute and the taiRangeList attribute indicate that the SMF can be selected for any TAI in the serving network. |
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taiRangeList |
array(TaiRange) |
O |
1..N |
The range of TAIs the SMF can serve. It contains the non-3GPP access TAI. The absence of this attribute and the taiList attribute indicate that the SMF can be selected for any TAI in the serving network. |
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priority |
integer |
O |
0..1 |
Priority (relative to other NFs of the same type) in the range of 0-65535, to be used for NF selection for a service request matching the attributes of the SmfInfo; lower values indicate a higher priority. See the precedence rules in the description of the priority attribute in NFProfile, if Priority is also present in the nfServiceList parameters or in NFProfile. The NRF overwrites the received priority value when exposing an NFProfile with the Nnrf_NFDiscovery service. |
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NOTES:
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SmfInfo in NFProfile is sent if there’s no change in configuration (all tai-groups data being sent without priority).
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SmfInfoList map is a new element in NFprofile.
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Each SmfInfoList entry doesn't contain all tai-group-list data. Each element contains entries of the same priority tai-groups per NSSAI.
NoteAll tai-groups under a slice is expected to be of the same priority.
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If tai-group-list has tai-groups of different priority configured under a slice, tai-groups are logically grouped based on priority. SmfInfo has data of tai-group of one priority and subsequent priority tai-group(s) data in each of SmfInfoList entry.
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If no tai-group is associated with any slice, then old behaviour prevails. If there’s tai-group association for few slices and few without, then the smfinfolist entries of slices without tai-group have no TAI details.
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For any tai-group if priority isn’t defined, it’s grouped separately and sent as a SmfInfo entry or different SmfInfoList entry.
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Key for each SmfInfoList map element is incremental counter string.