Content for &nbsp; TS 23.435 &nbsp; Word version:&nbsp; 19.3.0

VAL server sends VAL server policy provisioning request to NSCE server. The request contains the policy, VAL server ID, Default policy indication, and S-NSSAI. Optionally, the request contains the indicator of policy harmonization.

The VAL server can request the NSCE server to mark the provisioned policy as the default policy using the Default policy indication. The default policy should serve as a VAL server policy for the slices provisioned without any policy. Either the policy or default policy indication can be provided by the VAL server.

The VAL server policy is in form of a policy profile which contains list of trigger events associated with the parameters and expected actions. It contains priority and scheduling information with pre-emption capability for the policies. The scheduling information schedules the policy by defining the schedule (start and end time) for the policy. The pre-emption capability provides another, already successfully provisioned policy to pre-empt the scheduled policy in the scheduled period.

The supported policies are:

Based on monitored performance metric from OAM, when the max number of PDU sessions or max number of UE is reached, trigger the slice modification with expected parameters.
Based on monitored Network Slice load from NSACF, when the number of PDU sessions or number of UE exceeds the threshold, trigger the slice modification with expected parameters.
Based on monitored Network Slice load predictions from NWDAF, when Network Slice load predictions (Predicted Number of PDU Session establishments at the Network Slice) exceeds the threshold with high confidence, trigger the slice modification with expected parameters.
Based on the monitored the time period, when getting to a certain time period (e.g. summer vacation, spring festival etc.), trigger the slice modification with expected parameters.
Based on the monitored time period, when getting to a certain time period, trigger the slice modification based on the expected QoS per UE. QoS is mapped/calculated by NSCE to specific parameters of the slice such as the dLThptPerUE, uLThptPerUE, dLThptPerSliceSubnet, uLThptPerSliceSubnet, delayTolerance, dLLatency, uLLatency.

The NSCE server checks whether the policy is conflict with the MNO policies or NSPP. One criterion is to translate the network slice parameters in the service profile to see whether it is conflict with that in the VAL provided policy. If policy harmonization is not requested and policies conflict then the request could be rejected. The NSCE server also checks the validity of the policy (policy is valid for the specified time period or until the specified threshold count of trigger events is achieved) to avoid a ping-pong effect of slice modification. If the policy is invalid, the request could be rejected.

Figure 9.5.2.1.2-1: VAL server policy update

If the policy harmonization is requested, the NSCE server can harmonize the policy as per clause 9.5.2.1.4 and this may result in the changes to the current VAL server policy under provisioning.

Step 4.

NSCE server sends the VAL server policy provisioning response to the VAL server to indicate whether the request is successful or not. If it is successful, policy ID is provided to VAL server.

9.5.2.1.2 VAL server policy Update p. 37

Figure 9.5.2.1.2-1 illustrates the VAL server policy update procedure.

Pre-conditions:

The NSCE server has information about the existing slice/slice profile/slice services that the VAL server is using.
The VAL server has created policies in NSCE server using the procedure defined in clause 9.5.2.1.1.

Reproduction of 3GPP TS 23.435, Fig. 9.5.2.1.2-1: VAL server policy update

VAL server sends VAL server policy update request to NSCE server. The request shall contain the policy ID and policy modification details for updating the policy in the NSCE server. The request can update the existing default policy or specify a new default policy for the mentioned slice in the request. The policy update procedure can update the scheduling and pre-emption information for the policy.

The NSCE server checks whether the policy is conflict with the MNO policies or NSPP.

Figure 9.5.2.1.3-1: VAL server policy delete

If authorized, the NSCE server can harmonize the policy as per clause 9.5.2.1.4 and this may result in the changes to the current VAL server policy under update process.

Step 4.

If the VAL server is authorized to update the VAL server policy, the NSCE server checks the modification with existing policies to avoid conflict and provides the response to the VAL server.

9.5.2.1.3 VAL server policy Delete p. 38

Figure 9.5.2.1.3-1 illustrates the VAL server policy delete procedure.

Pre-conditions:

The NSCE server has information about the existing slice/slice profile/slice services that the VAL server is using.
The VAL server has created one or more policies in NSCE server using the procedure defined in clause 9.5.2.1.1.

Reproduction of 3GPP TS 23.435, Fig. 9.5.2.1.3-1: VAL server policy delete

VAL server sends VAL server policy delete request to NSCE server. The request contains the policy ID, and optionally default policy indication. The default policy indicates the update of the default policy in the case of a delete request for the default policy. The policy delete procedure can be used to delete one or more policies.

Figure 9.5.2.1.4-1: Policy harmonization

If the VAL server is authorized to delete the VAL server policy, the NSCE server deletes the policy. In the case of a default policy delete request, the NSCE server first updates the default policy with the policy mentioned in the delete request and then deletes the old default policy. The NSCE server reports the outcome of the deletion of the requested policy with policy ID and priority for the new default policy.

9.5.2.1.4 Policy harmonization p. 39

Policy harmonization is to make sure the VAL server Policy (from VAL Provider/ slice customer/ASP) is compatible with the MNO policies and NSCE service provider policy for the same service or slice. The policy harmonization could be requested through the policy provisioning/update service.

Figure 9.5.2.1.4-1 illustrates the procedure for policy harmonization.

Pre-conditions:

The NSCE service provider policy (NSPP) and MNO policy is available at the NSCE Server.
The VAL server is authorized to receive NSCE services.

Reproduction of 3GPP TS 23.435, Fig. 9.5.2.1.4-1: Policy harmonization

When receiving the policy provisioning, or policy update request, and the result of policy check turn out the policy is conflict, the policy harmonization is triggered.

The NSCE server determines parameters harmonizing the policy, if previously authorized.

Figure 9.5.2.1.5-1: VAL server policy usage reporting data

NSCE server sends the VAL server a notification providing parameters values that allow the policies to be harmonized. Then the VAL server would decide whether to accept the provided optional parameters values. If they are accepted, the VAL server may invoke VAL server policy provisioning/ VAL server policy update procedure defined in clause 9.5.2.1.1, 9.5.2.1.2 with harmonized parameters values.

9.5.2.1.5 VAL server policy Usage Reporting data p. 39

Figure 9.5.2.1.5-1 illustrates the VAL server policy usage reporting data procedure.

Pre-conditions:

The NSCE server has information about the existing slice/slice profile/slice services which VAL server is using.
The VAL server has created one or more policies using in the NSCE server the procedure defined in clause 9.5.2.1.1.

Reproduction of 3GPP TS 23.435, Fig. 9.5.2.1.5-1: VAL server policy usage reporting data

VAL server sends VAL server policy usage reporting data subscribe request to NSCE server. The request contains the policy ID, reporting interval, and the required duration of the data.

The NSCE server responds with a VAL server policy usage reporting data subscribe response message indicating the success or failure of the subscription.

Figure 9.5.2.2-1: Network slice optimization based on VAL server policy

The NSCE server reports the policy reporting data containing the number of times the policy has been used and the duration for which the policy was active in the requested duration and details of the preemption of policies. The reporting interval enables the periodic reporting of the requested report.

9.5.2.2 Network slice optimization based on VAL server policy p. 40

Figure 9.5.2.2-1 illustrates the procedure of network slice optimization based on VAL server policy.

Pre-conditions:

The NSCE server is authorized to get network slice management data notification from OAM, and/or NWDAF via NEF.
The VAL server is authorized to the NSCE server for network slice optimization.
There is enough network capacity when the expected action is to expand the network slice.
The VAL server policy has been pre-configured on the VAL server.
The VAL server policy has been provided to the NSCE server as specified in clause 9.5.2.1.

Reproduction of 3GPP TS 23.435, Fig. 9.5.2.2-1: Network slice optimization based on VAL server policy

VAL server sends network slice optimization subscription request to NSCE server. The request contains the policy ID indicating the different policies. Optionally the request contains the Secondary policy ID indicating the fallback policy to be used for the failed network slice optimization. The NSCE server retries the network slice optimization using a Secondary policy in the case of a failed optimization.

The NSCE server translates the trigger event to service API(s) with necessary parameters, and subscribe to the related service if needed.

To get the monitored performance metric from OAM, the notifyThresholdCrossing as defined in clause 11.3.1.3 of TS 28.532 which is filled in with corresponding S-NSSAI in objectInstance could be used.
To obtain the Network Slice load predictions from NWDAF, the NSCE server subscribes to the NWDAF prediction by invoking Nnef_AnalyticsExposure_Subscribe or Nnef_AnalyticsExposure_Fetch as defined in clauses 6.1.1.2 and 6.1.1.2 of TS 23.288.
To monitor the Network Slice load (e.g. the number of UEs or the number of PDU Sessions) from NSACF, the NSCE server subscribes to the NSACF by using the Nnef_EventExposure_Subscribe Request or Nnsacf_SliceEventExposure_Subscribe_Request as defined in clause 4.15.3.2.10 of TS 23.502, and the APIs defined in clause 6.2 of TS 29.536 can be utilized.
To monitor the time period, the NSCE server setup the timer.

Figure 9.5.2.3-1: Network slice optimization report retrieval

NSCE server sends the network slice optimization subscription response to the VAL server to confirm the subscription of network slice optimization.

Step 4.

Upon receiving the notification which indicating the trigger event is met, i.e., the monitored information reaches the threshold or specific time period is arrived, the NSCE server performs the expected action by triggering the slice modification as specified in the VAL server policy. The network slice modification could be triggered by consuming the Network Slice Provisioning service with the modifyMOIAttributes operation as specified in TS 28.531. The OAM responds back to NSCE server that the requested slice modification was successful or not. The slice modification requests contain the parameters need to be updated to fit the requirement of network slice (e.g., scale in or scale out the network slice capability), including at least one of the following, uLThptPerSlice, dLThptPerSlice, dLThptPerUE, uLThptPerUE, dLThptPerSliceSubnet, uLThptPerSliceSubnet, delayTolerance, dLLatency, uLLatency, maximum number of UEs, maximum number of PDU session as specified in TS 28.541.

Step 5.

The NSCE server provides a network slice optimization notification to the VAL server. The successful response optionally includes the Optimization time and the Enforced policy ID. The optimization time indicates the time the NSCE server has taken to optimize the slice. The Enforced policy ID indicates which secondary policy is used by the NSCE server for slice optimization in the case of a failed attempt for network slice optimization.

9.5.2.3 Network slice optimization report retrieval p. 41

Figure 9.5.2.3-1 illustrates the Network slice optimization report retrieval procedure.

Pre-conditions:

The NSCE server has information about the existing slice/slice profile/slice services that the VAL server is using.
The VAL server has the created policies using the procedure defined in clause 9.5.2.1.1.
The VAL server has subscribed for the network slice optimization using the procedure defined in clause 9.5.2.2.

Reproduction of 3GPP TS 23.435, Fig. 9.5.2.3-1: Network slice optimization report retrieval

The VAL server sends a Network slice optimization report request to the NSCE server. The request shall contain the subscription ID, optimization result window, and optional elements like optimization result filters, sorting rules, and result size. The VAL server creates a filter using the optimization result filter for the NSCE server requesting filtered successful or failed responses. The VAL server can create additional sorting rules for the NSCE server to request sorted results based on optimization time or policy ID or slice optimization event time in ascending or descending order. The result size indicates the number of results or responses for the report.