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Content for  TR 23.973  Word version:  17.0.0

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0  Introductionp. 5

During the network migration to 5GC, it is possible for operators to deploy separate HSS and UDM/UDR in e.g. multi-vendor scenario. This document describes the scenarios of separate UDM and HSS with separate repositories and with a common repository, and provides the corresponding solutions for these scenarios.

1  Scopep. 5

This Technical Report describes scenarios for co-existence of subscription data pertaining to legacy system (EPS) with data pertaining to the 5G system, when the HSS+UDM defined in Rel-15 is separated and both UDM and HSS are independent, and provides solutions to support this deployment where necessary.
This technical report includes:
  • diverse scenarios related to the storage of subscription data including, but not limited to, those of common repository for subscription data from EPS and 5GS, as well as separate repositories for EPS and 5GS subscription data; and
  • the solutions supporting relevant procedures in TS 23.502 (for e.g. authentication, mobility, handover and procedures for IMS and SMS handling in interworking between 5G system and EPS),
Provisioning aspects are out of the scope of this document.
Direct interactions between the EPS UDR and the 5GS UDR are out of the scope of this document.

2  Referencesp. 6

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
TR 21.905: "Vocabulary for 3GPP Specifications".
TS 23.502: "Procedures for the 5G System".
TS 23.335: "User Data Convergence (UDC); Technical realization and information flows; Stage 2".
TS 29.335: "User Data Convergence (UDC); User data repository access protocol over the Ud interface; Stage 3".
TS 23.002: "Network architecture".
TS 23.501: "System Architecture for the 5G System".
TS 23.228: "IP Multimedia Subsystem".
TS 23.380: "IMS Restoration Procedures".
TS 29.505: "5G System; Usage of the Unified Data Repository services for Subscription Data".
TS 29.228: "IP Multimedia (IM) Subsystem Cx and Dx Interfaces; Signalling flows and message contents".
TS 29.328: "IP Multimedia (IM) Subsystem Sh interface; Signalling flows and message contents".
TS 33.501: "Security architecture and procedures for 5G System".
TS 33.401: "System Architecture Evolution (SAE) - Security architecture".
TS 23.794: "Study on Enhanced IMS to 5GC Integration".
TS 23.060: "General Packet Radio Service (GPRS); Service description; Stage 2".
TS 23.401: "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access".
TS 24.229: "IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3".
TS 29.214: "Policy and charging control over Rx reference point".
TS 23.632: "User data interworking, coexistence and migration; Stage 2".
TS 29.563: "5G System (5GS); Home Subscriber Server (HSS) services for interworking with Unified Data Management (UDM); Stage 3".
TS 23.040: "Technical realization of the Short Message Service (SMS)".
TS 23.204: "Support of SMS over generic 3GPP IP access; Stage 2".
TS 29.272: "Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol".

3  Definitions and abbreviationsp. 7

3.1  Definitionsp. 7

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.
5G Repository:
Repository hosting subscription data for 5G UEs.
term used to identify the Unified Data Repository defined in TS 23.501, clause 4.2.5).
term used to identify the User Data Repository defined in TS 23.335, clause 4.2.3).

3.2  Abbreviationsp. 7

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
5G Core
5G System
5G Unified Data Repository
Home Subscriber Server Front End
Enhanced Packet core System
EPS User Data Repository
Evolved Universal mobile telecommunications system Terrestrial Radio Access Network
Unified Data Management

4  Architectural Assumptions and Principlesp. 8

4.1  Architectural Assumptionsp. 8

The 5GS data storage architecture defined in TS 23.501, for structured data, is used as the baseline network architecture.
The User Data Convergence concept specified in TS 23.335, is used for reference to EPS/legacy system architecture for data storage, when layered architecture is deployed (i.e. application front-end decoupled from data repository using the standard interface Ud defined in TS 29.335).
The Home Subscriber Server (HSS) architecture specified in clause 4.1.1 of TS 23.002, is used for reference to EPS/legacy system architecture for data storage, when non-layered HSS architecture is deployed (i.e. monolithic deployment where user data are stored within the entity itself (or in an external entity via non-standard interfaces)).

4.2  Architectural Principlesp. 8

In the UDC concept used for reference, HSS FE and EPS UDR defined in TS 23.335 are assumed to interact for any data required by the study: no standardization will be considered for the interface between HSS FE and EPS UDR.

5  Deployment Scenariosp. 8

This document supports the following deployment scenarios:
Scenario 1:
the HSS FE and` UDM are separately deployed and the user data of 5GC, EPC, CS and IMS domains are also stored separately in different repositories (i.e. EPS UDR storing user data for EPC, CS and IMS domains, and 5GC UDR storing user data for 5GS domain). It is assumed that the HSS is deployed using the UDC architecture in TS 23.335.
Scenario 2:
a common repository (acting as EPS UDR and 5GS UDR) is shared between separate HSS and UDM, in which both the user data for 5GC, EPC, CS and IMS domains are stored. It is also assumed that the HSS is deployed using the UDC architecture in TS 23.335.

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