AA (Normative)  Support of SBA in IMS |R16|  Word‑p. 337

AA.1  General

AA.1.0  Overview

This Annex AA describes support for SBA for IMS nodes. This Annex is intended to be used in conjunction with 5GC.

AA.1.1  Architectural Support

Figure AA.1.1-1 shows the architecture to support SBA interactions between IMS entities.

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Figure AA.1.1-1: System Architecture to support SBA in IMS

Figure AA.1.1-2 shows the architecture using the reference point representation.

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Figure AA.1.1-2: System Architecture to support SBA in IMS in reference point representation

AA.1.2  Reference point to support SBA in IMS

Following reference points are realized by service-based interfaces in IMS:

N5:

Reference point between the PCF and an AF.

N70:

Reference point between an SBI capable I/S-CSCF and an SBI capable HSS.

N71:

Reference point between an SBI capable IMS AS and an SBI capable HSS.

AA.1.3  Service based interface to support SBA in IMS

Npcf:

Service-based interface exhibited by PCF.

Nhss:

Service-based interface exhibited by an SBI capable HSS.

These SBI services provide equivalent functionality to the Diameter Rx and Cx/Sh reference points.

To support co-existence of IMS nodes supporting SBA services and IMS nodes not supporting SBA services SBI enabled IMS nodes may support both SBI and non-SBI interfaces.

AA.2  IMS SBA Services  Word‑p. 338

AA.2.1  HSS Services

AA.2.1.1  General

The following table shows the services exposed by an SBI capable HSS.

Table AA.2.1.1-1: IMS Services provided by an SBI capable HSS

Service	Service Operations	Operation Semantics	Example Consumer(s)
imsSubscriber Data Management (_ImsSDM)	Get	Request/Response	S-CSCF, I-CSCF, AS
	Subscribe	Subscribe/Notify	S-CSCF, AS
	Unsubscribe	Subscribe/Notify	S-CSCF, AS
	Notification	Subscribe/Notify	S-CSCF, AS
	Update	Request/Response	AS
imsUE Context Management (_ImsUECM)	Registration	Request/Response	S-CSCF
	DeregistrationNotification	Subscribe/Notify	S-CSCF
	Deregistration	Request/Response	S-CSCF
	Authorize	Request/Response	I-CSCF
	Update	Request/Response	S-CSCF
	RestorationInfoGet	Request/Response	S-CSCF
	RestorationInfoUpdate	Request/Response	S-CSCF
ImsUE Authentication	Get	Request/Response	S-CSCF

AA.2.1.2  Nhss_ImsUEContextManagement (ImsUECM) service

AA.2.1.2.1  Nhss_ImsUECM_Registration service operation

Service operation name:

Nhss_ImsUECM_Registration

Description:

This service operation registers the serving S-CSCF assigned to an IMS User. If authentication is not to be performed, this operation also sets the registration state. The S-CSCF is implicitly subscribed to be notified when it is deregistered in HSS. This notification is done by means of Nhss_ImsUECM_DeregistrationNotification operation.

Inputs, Required:

Public Identity, S-CSCF name, Registration Type (e.g. Initial Registration, Unregistered).

Inputs, Optional:

Private Identity.

Outputs, Required:

Result indication.

Outputs, Optional:

List of registered Private Identities sharing the same Public Identity which is being registered, S-CSCF Restoration indication.

AA.2.1.2.2  Nhss_ImsUECM_Deregistration service operation

Service operation name:

Nhss_ImsUECM_Deregistration

Description:

This service operation deregisters the S-CSCF allocated to a public identity.

Inputs, Required:

S-CSCF name, Deregistration Type.

Inputs, Optional:

User Identity (Private Identity and/or Public Identity), P-CSCF Restoration indication, Session Priority.

Outputs, Required:

Result indication.

Outputs, Optional:

None.

AA.2.1.2.3  Nhss_ImsUECM_DeregistrationNotification service operation  Word‑p. 339

Service operation name:

Nhss_ImsUECM_DeregistrationNotification

Description:

This service operation enables HSS to inform a S-CSCF which has previously registered in HSS of a Public Identity deregistration. This notification corresponds to an implicit subscription.

Inputs, Required:

Private Identity, Reason for Deregistration.

Inputs, Optional:

Public Identity, Associated Private Identities.

Outputs, Required:

Result indication.

Outputs, Optional:

Associated Private Identities, Identities with Emergency Registration.

AA.2.1.2.4  Nhss_ImsUECM_Authorize service operation

Service operation name:

Nhss_ImsUECM_Authorize

Description:

This service operation is used by the I-CSCF to request authorization from HSS for:

• The registration of a Public Identity by a UE in a P-CSCF network identifier according to the IMS User's subscription and operator limitations/restrictions.
• The reception of a terminating request based on the user state and IMS user's subscription (e.g. IMS User's barring status).

If the IMS User is authorized, the HSS may provide the address of the S-CSCF assigned to the Public Identity if any.

Additionally, this service operation is used to authorize in HSS a S-CSCF reselection (e.g. after I-CSCF detection if a S-CSCF failure).

Inputs, Required:

Public Identity, Authorization Type.

Inputs, Optional:

Private User Identity, P-CSCF network identifier.

Outputs, Required:

Result indication.

Outputs, Optional:

S-CSCF name.

AA.2.1.2.5  Nhss_ImsUECM_Update service operation

Service operation name:

Nhss_ImsUECM_Update

Description:

This service operation updates the registration state of a Public Identity or Private Identity in HSS i.e. to update the registration state from Not Registered or Unregistered to Registered state.

Inputs, Required:

Public Identity, S-CSCF name.

Inputs, Optional:

Private Identity.

Outputs, Required:

Result indication.

Outputs, Optional:

None.

AA.2.1.2.6  Nhss_ImsUECM_RestorationInfoGet service operation  Word‑p. 340

Service operation name:

Nhss_ImsUECM_RestorationInfoGet

Description:

This service operation is used between the S-CSCF and the HSS to retrieve information from HSS to support the S-CSCF procedures.

Inputs, Required:

Public Identity.

Inputs, Optional:

Private Identity.

Outputs, Required:

Result Indication.

Outputs, Optional:

Restoration data.

AA.2.1.2.7  Nhss_ImsUECM_RestorationInfoUpdate service operation

Service operation name:

Nhss_ImsUECM_RestorationInfoUpdate

Description:

This service operation is used between the S-CSCF and the HSS to update information in HSS to support the S-CSCF Restoration procedures.

Inputs, Required:

Private Identity, Public Identity, Restoration data.

Inputs, Optional:

None.

Outputs, Required:

Result indication.

Outputs, Optional:

None.

AA.2.1.3  Nhss_ImsSubscriberDataManagement (ImsSDM) service

AA.2.1.3.1  General

IMS Subscriber data types used in the Nhss_ImsSDM Service are defined in Table AA.2.1.3.1-1 below.

Table AA.2.1.3.1-1: IMS Subscriber data types

IMS Subscriber data	Description
Service Profile Data	This may include e.g. service parameters, the S-CSCF allocated to a public identity or the list of S-CSCFs and their capabilities, Application Server address, triggers, information on subscribed media, profile parameters (e.g. barring indicator, etc.) as defined in TS 29.228. Service Profile Data is consumed by CSCF.
Repository Data	Data that is understood syntactically but not semantically by the HSS (unstructured Data). It is data that an AS may store in the HSS to support its service logic. One example is data that an AS stores in the HSS, using it as a repository. Service Indication identifies the set of service related transparent data associated to a Public Identity. Repository Data is consumed by IMS-AS.
Non-Transparent Data	Data that is understood both syntactically and semantically by the HSS e.g. location information. Non-Transparent Data is structured using data references as defined in TS 29.328. Non-Transparent Data is consumed by IMS-AS.

At least a mandatory key is required for each IMS Subscriber Data Type to identify the corresponding data as defined in Table AA.2.1.3.1-2 below.

Table AA.2.1.3.1-2: IMS Subscriber data types keys

IMS Subscriber Data Types	Data Key	Data Sub Key
Service Profile Data	Public Identity
Repository Data	Public Identity	Service Indication
Non-Transparent Data	See NOTE 1

AA.2.1.3.2  Nhss_ImsSDM_Get service operation  Word‑p. 341

Service operation name:

Nhss_ImsSDM_Get

Description:

This service operation enables the NF consumer to fetch the service profile data, repository data, and non-transparent data references for an IMS User.

The HSS shall check that the requested NF consumer is authorized to fetch the requested data. In the case that the requested data is Repository data, the HSS may also authorize based on service indication.

Inputs, Required:

NF Type, IMS Subscriber data type(s), Key for each IMS Subscriber data type(s).

Inputs, Optional:

Application Service Identity.

Outputs, Required:

Result indication.

Outputs, Optional:

Requested Data.

AA.2.1.3.3  Nhss_ImsSDM_Subscribe service operation

Service operation name:

Nhss_ImsSDM_Subscribe

Description:

The NF consumer subscribes for updates to requested data. HSS shall check that the requested NF consumer is authorized to subscribe to requested updates.

Inputs, Required:

NF Type, IMS Subscriber data type(s), Key for each IMS Subscriber data type(s).

Inputs, Optional:

Application Server Identity.

Outputs, Required:

When the subscription is accepted: Subscription Correlation ID.

Outputs, Optional:

None.

AA.2.1.3.4  Nhss_ImsSDM_Unsubscribe service operation

Service operation name:

Nhss_ImsSDM_Unsubscribe

Description:

The NF consumer unsubscribes for updates to Requested data.

Inputs, Required:

Subscription Correlation ID.

Inputs, Optional:

None.

Outputs, Required:

Result.

Outputs, Optional:

None.

AA.2.1.3.5  Nhss_ImsSDM_Notification service operation

Service operation name:

Nhss_ImsSDM_Notification

Description:

This service operation enables HSS to notify a NF of any changes to what the NF subscribed to.

Inputs, Required:

IMS Subscriber data type(s), Key for each IMS Subscriber data type(s).

Inputs, Optional:

None.

Outputs, Required:

Result indication.

Outputs, Optional:

None.

AA.2.1.3.6  Nhss_ImsSDM_Update service operation  Word‑p. 342

Service operation name:

Nhss_ImsSDM_Update

Description:

The NF consumer updates HSS subscription data if authorized to do so.

Inputs, Required:

NF Type, IMS Subscriber data type(s), Key for each IMS Subscriber data type(s).

Inputs, Optional:

Application Service Identity.

Outputs, Required:

Result.

Outputs, Optional:

None.

AA.2.1.4  Nhss_ImsUEAuthentication service

AA.2.1.4.1  Nhss_ImsUEAuthenticate_Get service operation

Service operation name:

Nhss_ImsUEAuthenticate_Get

Description:

This service operation is used between the S-CSCF and the HSS to exchange information to support the authentication between the end user and the home IMS network.

Inputs, Required:

Private User Identity, Public User Identity, Authentication Data (Authentication Scheme).

Inputs, Optional:

Authentication Data (Authentication Context, Authorization Information).

Outputs, Required:

Result Indication.

Outputs, Optional:

User Identity, Authentication Data (e.g. AV).

AA.2.2  Mapping of Cx and Sh operations and terminology to HSS SBI services

AA.2.2.1  General

This clause gives mappings from Cx and Sh operations to HSS SBI services and service operations.

AA.2.2.2  Mapping of Cx messages to HSS SBI services

The following table defines the mapping between stage 2 Cx messages and HSS SBI services and service operations:

Table AA.2.2.2-1: Cx messages to HSS SBI services and service operations mapping

Cx message	Source	Destination	HSS SBI service operation name
Cx-Query	I-CSCF	HSS	Nhss_ImsUECM_Authorize
Cx-Select-Pull	I-CSCF	HSS	Nhss_ImsSDM_Get (see NOTE 1)
Cx-Put	S-CSCF	HSS	Nhss_ImsUECM_Registration (see NOTE 2) Nhss_ImsUECM_Deregistration (see NOTE 3) Nhss_ImsUECM_Update (see NOTE 4) Nhss_ImsUECM_RestorationInfoUpdate (see NOTE 5)
Cx-Pull	S-CSCF	HSS	Nhss_ImsSDM_Get (see NOTE 6) Nhss_ImsSDM_Subscribe (see NOTE 6) Nhss_ImsSDM_Unsubscribe Nhss_ImsUECM_RestorationInfoGet (see NOTE 7)
Cx-Location-Query	I-CSCF	HSS	Nhss_ImsUECM_Authorize Nhss_ImsSDM_Get (see NOTE 8)
Cx-AuthDataReq	S-CSCF	HSS	Nhss_ImsUECM_Registration (see NOTE 9) Nhss_ImsUEAuthenticate_Get
Cx-Deregister	HSS	S-CSCF	Nhss_ImsUECM_DeregistrationNotification
Cx-Update_Subscr_Data	HSS	S-CSCF	Nhss_ImsSDM_Notification

AA.2.2.3  Mapping of Sh messages to HSS SBI services  Word‑p. 343

The following table defines the mapping between stage 2 Sh messages and HSS SBI services and service operations:

Table AA.2.2.3-1: Sh messages to HSS SBI services and service operations mapping

Sh message	Source	Destination	HSS SBI service operation name
Sh-Pull	AS	HSS	Nhss_ImsSDM_Get
Sh-Update	AS	HSS	Nhss_ImsSDM_Update
Sh-Subs-Notif	AS	HSS	Nhss_ImsSDM_Subscribe Nhss_ImsSDM_Unsubscribe Nhss_ImsSDM_Get
Sh-Notif	HSS	AS	Nhss_ImsSDM_Notification

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