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.

NFProfile

smfInfo

SmfInfo

O

0..1

Specific data for the SMF (DNNs).

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.

Note

The absence of both the smfInfo and smfInfoList attributes in an SMF profile indicates that the SMF can be selected for any S-NSSAI, DNN, TAI, and access type.

SMFInfo

Attribute Name

Data Type

P

Cardinality

Description

sNssaiSmfInfoList

array(sNssaiSmfInfoItem)

M

1..N

List of parameters supported by the SMF per S-NSSAI.

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.

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.

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.

Note

An SMF profile may contain multiple SmfInfo entries, with each entry containing a different list of TAIs and a different priority, to differentiate the priority to select the SMF based on the user location. The priority in SmfInfo has the least precedence, that is. it applies between SMFs or SMF Services with the same priority.

NOTES:

  • SmfInfo in NFProfile is sent if there’s no change in configuration (all tai-groups data being sent without priority).

  • SmfInfoList map is a new element in NFprofile.

  • Each SmfInfoList entry doesn't contain all tai-group-list data. Each element contains entries of the same priority tai-groups per NSSAI.

    Note

    All tai-groups under a slice is expected to be of the same priority.

  • 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.

  • 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.

  • For any tai-group if priority isn’t defined, it’s grouped separately and sent as a SmfInfo entry or different SmfInfoList entry.

  • Key for each SmfInfoList map element is incremental counter string.