5.2.16 NSSF Services
23.5023GPPProcedures for the 5G System (5GS)Release 18TS
5.2.16.1 General
The following table illustrates the NSSF Services.
Table 5.2.16.1-1: NF Services provided by NSSF
|
Service Name |
Service Operations |
Operation Semantics |
Example Consumer(s) |
|
Nnssf_NSSelection |
Get |
Request/Response |
AMF, NSSF in a different PLMN, SMF, NWDAF |
|
Nnssf_NSSAIAvailability |
Update |
Request/Response |
AMF |
|
Subscribe |
Subscribe/Notify |
AMF |
|
|
Unsubscribe |
AMF |
||
|
Notify |
AMF |
||
|
Delete |
Request/Response |
AMF |
NOTE: The SMF uses the Nnssf_NSSelection_Get service operation during EPS interworking.
5.2.16.2 Nnssf_NSSelection service
5.2.16.2.1 Nnssf_NSSelection_Get service operation
Service operation name: Nnssf_NSSelection_Get
Description: This service operation enables Network Slice selection in both the Serving PLMN and HPLMN. It also enables the NSSF to provide to the AMF the Allowed NSSAI and the Configured NSSAI for the Serving PLMN. It allows also to provide the NSAG information which is applicable (clause 5.15.14 of TS 23.501 [2]).
It may be invoked during Registration procedure, during inter-PLMN mobility procedure, during PDU Session Establishment procedure or during UE Configuration Update procedure. When invoked during Registration procedure it may possibly trigger AMF re-allocation. When invoked during PDU Session Establishment procedure it may be invoked in the VPLMN or in the HPLMN; if invoked in the VPLMN it returns the hNRF selected by the hNSSF and, if applicable, the value of the HPLMN NSI ID. When invoked during UE Configuration Update procedure or inter-PLMN mobility procedure it may be invoked in the Serving PLMN.
NOTE 1: The list of events, which trigger invoking of the Nnssf_NSSelection_Get service operation, is not exhaustive.
NOTE 2: The NSSF can determine the serving network and Access Type from the TAI, as described in TS 29.571 [70].
Inputs, Required: None.
Inputs, Conditional Required:
If this service operation is invoked during Registration procedure for Network Slice selection or UE Configuration Update procedure, then the following inputs are required:
– Subscribed S-NSSAI(s) with the indication if marked as default S-NSSAI, PLMN ID of the SUPI, TAI, NF type of the NF service consumer, Requester ID.
If this service operation is invoked to derive the S-NSSAI for the serving PLMN (as described in clause 4.11.1.3.3), the following inputs are required:
– S-NSSAIs for the HPLMN associated with established PDN connection, PLMN ID of the SUPI, NF type of the NF service consumer, Requester ID.
If this service operation is invoked by target AMF during inter-PLMN mobility procedure, the following inputs are required:
– S-NSSAIs for the HPLMN, PLMN ID of the SUPI, TAI.
If this service operation is invoked during PDN Connection Establishment in the Serving PLMN in EPS by a SMF+PGW-C, the following inputs are required:
– Subscribed S-NSSAIs for the UE, PLMN ID of the SUPI, NF type of the NF service consumer, Requester ID.
If this service operation is invoked during PDU Session Establishment procedure in the Serving PLMN then the following inputs are required:
– S-NSSAI, non-roaming/LBO roaming/HR roaming indication, PLMN ID of the SUPI, TAI, NF type of the NF service consumer, Requester ID.
Inputs, Optional:
If this service operation is invoked during Registration procedure for Network Slice selection or UE Configuration Update procedure, then the following inputs are provided if available:
– Requested NSSAI, Mapping Of Requested NSSAI, Default Configured NSSAI Indication, NSSRG Information, UE support of subscription-based restrictions to simultaneous registration of network slice feature Indication, UDM indication to provide all subscribed S-NSSAIs for UEs not indicating support of subscription-based restrictions to simultaneous registration of network slices, Allowed NSSAI for current Access Type, Allowed NSSAI for the other Access Type and the corresponding Mapping Of Allowed NSSAIs for current Access Type and other Access Type, Rejected S-NSSAI(s) for RA, UE support of NSAG Information.
If this service operation is invoked during PDU Session Establishment procedure, then the following input is optional:
– HPLMN S-NSSAI that maps to the S-NSSAI from the Allowed NSSAI of the Serving PLMN.
Outputs, Conditional Required:
If this service operation is invoked during Registration procedure for Network Slice selection or UE Configuration Update procedure, then one or more of the following outputs are required:
– Allowed NSSAI, Configured NSSAI; Target AMF Set or, based on configuration, the list of candidate AMF(s).
If this service operation is invoked during inter-PLMN mobility procedure, then one or more of the following outputs are required:
– Allowed NSSAI.
If this service operation is invoked to derive the S-NSSAI for the serving PLMN (as described in clause 4.11.1.3.3), the following output is required:
– S-NSSAIs for the HPLMN associated with established PDN connection, Mapping of S-NSSAIs associated with established PDN connection in the Serving PLMN.
If this service operation is invoked during PDN Connection Establishment in the Serving PLMN in EPS by a SMF+PGW-C, the following outputs are required:
– Subscribed S-NSSAIs for the UE, Mapping of S-NSSAIs associated with the subscribed S-NSSAIs for the UE in the Serving PLMN.
If this service operation is invoked during PDU Session Establishment procedure, then the following outputs are required:
– The NRF to be used to select NFs/services within the selected Network Slice instance.
Outputs, conditional Optional:
If this service operation is invoked during UE Registration procedure or UE Configuration Update procedure, then one or more of the following outputs are optional:
– Mapping Of Allowed NSSAI, Mapping Of Configured NSSAI, NSI ID(s) associated with the Network Slice instances of the Allowed NSSAI, NRF(s) to be used to select NFs/services within the selected Network Slice instance(s) and NRF to be used to determine the list of candidate AMF(s) from the AMF Set, rejected S-NSSAI with cause of rejection, Target NSSAI, the NSAG information (defined in clause 5.15.14 of TS 23.501 [2]).
If this service operation is invoked during inter-PLMN mobility procedure, then the following output is optional:
– Mapping Of Allowed NSSAI.
If this service operation is invoked during PDU Session Establishment procedure, then the following output is optional:
– NSI ID associated with the S-NSSAI provided in the input.
5.2.16.3 Nnssf_NSSAIAvailability service
5.2.16.3.1 General
Service description: This service enables to update the AMFs and the NSSF on the availability of S-NSSAIs and NSAGs on a per TA basis.
NOTE: The NSSF can determine the serving network and Access Type from the TAI, as described in TS 29.571 [70].
5.2.16.3.2 Nnssf_NSSAIAvailability_Update service operation
Service operation name: Nnssf_NSSAIAvailability_Update
Description: This service operation enables the AMF to update the NSSF with the S-NSSAIs the AMF supports per TA and get the availability of the S-NSSAIs and optionally NSI IDs per TA for the S-NSSAIs the AMF supports.
Inputs, Required: Supported S-NSSAIs per TAI.
The supported S-NSSAIs per TAI, is a list of TAIs and for each TAI the S-NSSAIs supported by the AMF.
Inputs, Optional: Supported NSAGs per TAI..
The supported NSAGs per TAI, is a list of TAIs and for each TAI the NSAGs and the associated S-NSSAIs supported by the AMF.
Outputs, Required: A list of TAIs and, for each TAI, the S-NSSAIs and optionally NSI IDs supported by the AMF and 5G-AN and authorized by the NSSF for the TAI.
Outputs, Conditional Required: A list of TAIs and, for each TAI, the NSAGs authorized by the NSSF for the TAI.
The authorized NSAGs per TAI, is a list of TAIs and for each TAI the NSAGs and the associated S-NSSAIs.
Outputs, Optional: For each TAI, a list of S-NSSAIs restricted per PLMN for the TAI.
5.2.16.3.3 Nnssf_NSSAIAvailability_Notify service operation
Service operation name: Nnssf_NSSAIAvailability_Notify
Description: This service operation enables the NSSF to update a NF Service Consumer (e.g. AMF) with any S-NSSAIs restricted per TA and, if needed, subsequently lift any restriction per TA.
Inputs, Required: SubscriptionId, a list of TAIs and the S-NSSAIs for which the status is changed (restricted/unrestricted) per each TAI.
Inputs, Optional: NSI IDs in the S-NSSAI for which the status is changed (restricted/unrestricted) per each TAI.
Outputs, Required: None.
Outputs, Optional: None.
5.2.16.3.4 Nnssf_NSSAIAvailability_Subscribe service operation
Service operation name: Nnssf_NSSAIAvailability_Subscribe
Description: This service operation enables a NF Service Consumer (e.g. AMF) to subscribe to a notification of any changes in status of the NSSAI availability information (e.g. S-NSSAIs and optionally NSI IDs available per TA and the restricted S-NSSAI(s) and optionally NSI IDs per PLMN in that TA in the serving PLMN of the UE) upon this is updated by another AMF.
Inputs, Required: Callback URI of the NF Service Consumer, list of TAIs supported by the NF service consumer, event to be subscribed.
Inputs, Optional: Expiry time.
Outputs, Required: SubscriptionID,
Outputs, Conditional Required: Expiry time (if present in the request, may be included in the response based on operator’s policy and taking into account the expiry time present in the request (i.e. should be less than or equal to that value); if not present in the request, may be included in the response based on operator’s policy. Whatever the case, if not included in the response, this means that the subscription is valid without an expiry time).
Outputs, Optional: A list of TAIs and, for each TAI, the S-NSSAIs and optionally NSI IDs supported by the AMF and 5G-AN and authorized by the NSSF for the TAI and a list of S-NSSAIs and optionally NSI IDs restricted per PLMN for the TAI.
5.2.16.3.5 Nnssf_NSSAIAvailability_Unsubscribe service operation
Service operation name: Nnssf_NSSAIAvailability_Unsubscribe
Description: This service operation enables a NF Service Consumer (e.g. AMF) to unsubscribe to a notification of any previously subscribed changes to the NSSAI availability information.
Inputs, Required: SubscriptionId.
Inputs, Optional: None.
Outputs, Required: None.
Outputs, Optional: None.
5.2.16.3.6 Nnssf_NSSAIAvailability_Delete service operation
Service operation name: Nnssf_NSSAIAvailability_Delete
Description: This service operation enables a NF service consumer (e.g. AMF) to delete the NSSAI availability information stored for the NF service consumer in the NSSF.
Inputs, Required: NfId.
Inputs, Optional: None.
Outputs, Required: None.
Outputs, Optional: None.