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Content for  TS 23.435  Word version:  19.3.0

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9 Procedures and information flows  9.1 General  9.2 Registration  9.3 Slice API configuration and translation  9.3.1 General  9.3.2 Procedure  9.3.2.1 Procedures on slice API configuration  9.3.2.2 Procedure on slice API translation  9.3.3 Information flows  9.3.4 APIs  9.3.4.1 General  9.3.4.2 SS_NSCE_SliceApiConfiguration API  9.3.4.3 SS_NSCE_Slice_ApiInvocation API 
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9  Procedures and information flows  p. 23

9.1  General  p. 23

9.1.1  Common Information Elements  p. 23

9.1.1.1  General |R19|  p. 23

This clause provides descriptions for Information Elements which are commonly used in several procedures.

9.1.1.2  Service requirement  p. 23

The service requirement indicates the VAL application requirements pertaining to the slice(s).
Information element Status Description
VAL service IDMThe identification of the application ID related with the service requirement.
VAL service KPIsOKPIs including application QoS requirements (latency, error rates, throughput, jitter,..).
Network slice related identifier(s)MIdentifier of network slice for which the request applies.
Application layer Service ProfileO The properties of network slice related requirement. If Service Profile is known by the VAL server, it can be provided to the NSCE server. The GST defined by GSMA (see clause 2.2 in [5]) and the performance requirements defined in clause 7 of TS 22.261 are all considered as input for it.
Area of interestOThe service area for which the requirement applies, which can be expressed as a geographical area (e.g. geographical coordinates), or a topological area (e.g. a list of TA).
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9.2  Registration  p. 23

For registration of the VAL server to be a recognized user of the CAPIF, the VAL server triggers the CAPIF Onboarding the API invoker procedure defined in clause 8.1 of TS 23.222. The NSCE server could be deployed with CAPIF core function.
For de-registration of the VAL server, the VAL server triggers the CAPIF Offboarding the API invoker procedure defined in clause 8.2 of TS 23.222.
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9.3  Slice API configuration and translation  p. 23

9.3.1  General  p. 23

This functionality is a service related to the translation of the service API as invoked by the end applications to slice APIs based on the API configuration and application to slice mapping. Slice APIs can be defined as customized/tailored sets of service APIs (which can be either NEF northbound APIs or OAM provided APIs or enabler layer/SEAL provided APIs) and can be mapped to particular slice instances. The slice APIs can be a bundled or combined API comprising of different types of APIs, which will be used to expose the telco (5GS/SEAL)-provided services as needed by the applications of the slice customer. Each slice API may be configured per network slice instance.
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9.3.2  Procedure  p. 24

9.3.2.1  Procedures on slice API configuration  p. 24

9.3.2.1.1  General  p. 24
In the Initial Configuration procedure, the VAL server initially provides an application requirement to enabler server including the service KPIs and the subscribed/preferred slices. Then, the slice enabler configures the mapping of the VAL application to a slice API which is a combination/bundling of northbound APIs (from both management and control plane). In particular, a slice API consists of telco-provided/platform dependent service APIs (e.g., NEF, OAM, SEAL, etc), and provides an abstraction/simplification on top of them. The VAL server-initiated Configuration Update procedure covers the scenario where a trigger event occurs (e.g., QoS degradation, slice load) and the mapping configuration or the slice API configuration needed to be changed. In this scenario, the slice enabler updates the configuration of the API and provides a notification to the VAL server.
These two procedures for the initial configuration and the configuration update are covered in clause 9.3.2.1 and 9.3.2.2 respectively.
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9.3.2.1.2  Initial Configuration  p. 24
Figure 9.3.2.1.2-1 illustrates the procedure of the initial slice API configuration.
Pre-conditions:
  1. The VAL server has registered to receive NSCE services.
Reproduction of 3GPP TS 23.435, Fig. 9.3.2.1.2-1: Initial Slice API configuration
Figure 9.3.2.1.2-1: Initial Slice API configuration
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Step 1.
The VAL server sends a VAL application requirement request to the NSCE server. If CAPIF is used, the NSCE server acts as AEF, and the authorization is obtained from CCF.
Step 2.
The NSCE server maps the VAL application requirement to a slice API which includes a list of APIs which is needed to be consumed as part of this service capability exposure.
The NSCE server may also store the mapping of the slice API to the service API list and per service API information (e.g. data encoding, transport technology, API protocol and versions)
Step 3.
The NSCE server registers to consume the corresponding APIs from the 5GS (NEF and OAM) and SEAL service producers. The NSCE server registers to the following:
  • to consume NEF monitoring events as specified in clause 5 of TS 29.522 e.g., network monitoring, slice status, analytics exposure, etc
  • to consume PM services and KPI monitoring from OAM
  • to consume SEAL services based on TS 23.434
If CAPIF is used, the subscription/registration requests are sent to the corresponding AEFs of the API provider's domain, and the authorization is obtained by CCF. The preferred network slice related identifier received in step 1 is used by the NSCE server in requesting CCF authorization to consume the service provided by 5GS/SEAL.
Step 4.
The NSCE server sends a VAL application requirement response to notify on the result of the request and indicate whether the configuration of slice API is possible or not.
Step 5.
The NSCE server sends the slice API information notification to the VAL server.
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9.3.2.1.3  VAL server-initiated Configuration Update  p. 25
Figure 9.3.2.1.3-1 illustrates the procedure of the slice API configuration updated based on a trigger event.
Pre-conditions:
  1. Initial configuration of the slice API has been completed successfully.
  2. A trigger event, which may result the need of a slice configuration change, is captured by the VAL server (application server relocation to different EDN/DN, UE mobility to different EDN, application change of behaviour).
Reproduction of 3GPP TS 23.435, Fig. 9.3.2.1.3-1: Slice API configuration update
Figure 9.3.2.1.3-1: Slice API configuration update
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Step 1.
The VAL server sends a VAL server-initiated configuration update request to the NSCE server.
Step 2.
The NSCE server processes the trigger event and checks the feasibility of such change and updates the mapping of service APIs to the slice APIs. One criterion for the update of the mapping is, if possible, to avoid changing the slice API configuration, which can be achieved by the re-mapping of the underlying service APIs
Step 3.
The NSCE server updates the subscription/registration to the underlying 5GS and SEAL service producers, if an update on the service APIs (e.g., NEF APIs, SEAL APIs, OAM provided APIs) is needed.
Step 4.
The NSCE server sends a VAL server-initiated configuration update response, containing the new slice API information, if an update has been carried out by the NSCE server.
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9.3.2.2  Procedure on slice API translation  p. 25

This procedure follows the clause 9.3.2.1 and aims to describe how the slice API invocation request is translated to service API invocations after the slice API configuration mapping. In this procedure, the NSCE server initially receives a slice API invocation request from the vertical application. Then, the NSCE server fetches the service APIs to be invoked based on the slice API configuration and performs invocation requests to the corresponding service API providers.
Figure 9.3.2.2-1 illustrates the procedure of the slice API translation based on the initial configuration.
Pre-conditions:
  1. The VAL server has registered to receive NSCE services.
  2. The slice API mapping to the VAL server has been performed based on clause 9.3.2.1.2 step 2 and the slice API information is provided to the VAL server based on clause 9.3.2.1.2 step 5.
Reproduction of 3GPP TS 23.435, Fig. 9.3.2.2-1: Slice API translation
Figure 9.3.2.2-1: Slice API translation
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Step 1.
The VAL server sends a slice API invocation request to the NSCE server
Step 2.
The NSCE server checks that the user is authenticated and authorized to perform the slice API invocation and maps the requested slice API to a service APIs. If CAPIF is used, the NSCE server acts as AEF, and the authorization is obtained from CCF.
Step 3.
The NSCE server generates a trigger for service API invocation requests to all the service APIs within the slice API.
Step 4.
The NSCE server performs the corresponding service API invocation procedures based on CAPIF or via performing requests to the corresponding service API providers, which are mapped to the slice API.
If CAPIF is used, the requests are sent to the corresponding AEFs of the API provider's domain, and the authorization is obtained by CCF. The requested network slice related identifier received in step 1 is used by the NSCE server in requesting CCF authorization to consume the service provided by 5GS/SEAL.
Step 5.
The NSCE server sends a slice API invocation response to the VAL server, based on the result of the service API invocation response(s) of step 4.
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9.3.3  Information flows  p. 26

9.3.3.1  General  p. 26

The following information elements are specified for slice API translation and configuration specified in clause 9.3.2.1 and 9.3.2.2.

9.3.3.2  VAL application requirement request  p. 26

Table 9.3.3.2-1 describes information elements for the VAL application requirement request from the VAL server to the NSCE server.
This request provides the service requirements / KPIs, the capability exposure requirements and a preferred/subscribed slice identification (e.g., S-NSSAI or ENSI).
Information element Status Description
VAL server IDMThe identifier of the VAL server.
List of service requirement(s)M The VAL application requirements pertaining to the slice(s) as defined in Table 9.1.1.1-1.
Time validityOThe time validity of the request.
NOTE:
One of this shall be present.
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9.3.3.3  VAL application requirement response  p. 27

Table 9.3.3.3-1 describes information elements for the VAL application requirement response from the NSCE server to the VAL server.
Information element Status Description
ResultMIndicates the success or failure of the VAL application requirements request.
> CauseO
(see NOTE)		Indicates the cause of failure.
NOTE:
May only be present if the result is failure.
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9.3.3.4  Slice API information notify  p. 27

Table 9.3.3.4-1 describes information elements for the Slice API information notification from the NSCE server to the VAL server. The Slice API information notification is used by NSCE server to send Slice API information to VAL server in the Initial Configuration and Configuration Update procedures.
Information element Status Description
Slice API infoMThe information for the configured slice API.
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9.3.3.5  VAL server-initiated configuration update request  p. 27

Table 9.3.3.5-1 describes information elements of the VAL server-initiated configuration update request sent by the VAL server to the NSCE server.
Information element Status Description
VAL server IDMThe identifier of the VAL server.
Network slice IDOIdentifier of the network slice for which the API configuration update is requested.
Trigger Event DetailsM The trigger event details can be included, providing the cause for the need slice API configuration adaptation. Such trigger event can be:
  • the UE mobility to a different service area (outside the original area of interest),
  • application server migration to different edge/cloud platform,
  • service API unavailability,
  • VAL application QoS requirements change.
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9.3.3.6  VAL server-initiated configuration update response  p. 28

Table 9.3.3.6-1 describes information elements of the VAL server-initiated configuration update response sent by the NSCE server to the VAL server.
Information element Status Description
Configuration changedO
(see NOTE)		Indicates that the slice configuration has been changed.
> Updated slice API informationMThe information for the updated slice API.
Configuration not changedO
(see NOTE)		The trigger event details can be included, providing the cause for the need slice API configuration adaptation. Such trigger event can be
> CauseMIndicates the reason for not changing the slice configuration. The reason may be that no change was needed, failure of changing in 5GS/SEAL or other (e.g. server internal error).
NOTE:
Only one of these IEs is present in the message.
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9.3.3.7  slice API invocation request  p. 28

Table 9.3.3.7-1 describes information elements for the slice API invocation request from the VAL server to the NSCE server.
Information element Status Description
VAL server IDMThe identifier of the VAL server.
Authorization informationOThe authorization information obtained before initiating the slice API invocation request.
Slice API identificationMThe identification information of the slice API for which invocation is requested. The slice API identification is part of the specific slice API invocation request.
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9.3.3.8  slice API invocation response  p. 28

Table 9.3.3.8-1 describes information elements for the slice API invocation response from the NSCE server to the VAL server.
Information element Status Description
ResultMIndicates the success or failure of slice API invocation request.
> CauseO
(see NOTE)		Indicates the cause of failure.
NOTE:
May only be present if the result is failure.
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9.3.4  APIs  p. 28

9.3.4.1  General  p. 28

Table 9.3.4.1-1 illustrates the NSCE APIs for the slice API configuration and translation feature.
API Name API Operations Known Consumer(s) Communication Type
SS_NSCE_SliceApiConfigurationSlice_API_configurationVAL serverRequest /Response
Slice_API_configuration_updateVAL serverRequest /Response
Slice_API_information_notifyVAL serverNotify
SS_NSCE_Slice_ApiInvocationSlice_API_invocationVAL serverRequest /Response
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9.3.4.2  SS_NSCE_SliceApiConfiguration API  p. 29

9.3.4.2.1  General  p. 29
API description:
This API enables the VAL server to communicate with the NSCE server for the initial configuration of the slice API and possible subsequent slice API configuration update(s).
9.3.4.2.2  SS_NSCE_Slice_API_configuration  p. 29
API operation name:
Slice_API_configuration
Description:
Providing for VAL_Application_requirement to the NSCE server.
Known Consumers:
VAL server
Inputs:
See subclause 9.3.3.2
Outputs:
See subclause 9.3.3.3
9.3.4.2.3  SS_NSCE_Slice_API_configuration_update  p. 29
API operation name:
Slice_API_configuration_update
Description:
VAL server providing trigger event information to the NSCE server that may potentially invoke slice API configuration change(s).
Known Consumers:
VAL server
Inputs:
See subclause 9.3.3.5
Outputs:
See subclause 9.3.3.6
9.3.4.2.4  SS_NSCE_Slice_API_information_notify  p. 29
API operation name:
Slice_API_information_notify
Description:
Notifying the slice API information
Known Consumers:
VAL server
Inputs:
See subclause 9.3.3.4
Outputs:
None

9.3.4.3  SS_NSCE_Slice_ApiInvocation API  p. 29

9.3.4.3.1  General  p. 29
API description:
This API enables the VAL server to communicate with the NSCE server for invoking the slice API over NSCE-S.
9.3.4.3.2  SS_NSCE_Slice_API_invocation  p. 30
API operation name:
Slice_API_invocation
Description:
Requesting slice API invocation from NSCE server.
Known Consumers:
VAL server
Inputs:
See subclause 9.3.3.7
Outputs:
See subclause 9.3.3.8

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