Content for  TR 29.829  Word version:  17.1.0

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0  Introductionp. 7

In the Rel-16 architecture for 5G SMSoNAS (i.e. SMS over NAS), SMSF and the UDM are not able to expose service-based interfaces to an IP-SM-GW, SMS Router or SMS Center, As a result, SMSoNAS transport to/from the SMSF/UDM (e.g. towards IP-SM-GW, SMS Router, SMS Center, etc.) enabling to send MO / MT SMS is still carried out via legacy MAP or Diameter protocols.
This generates the following main issues:
  • No SBI-based interface is defined for enabling the retrieval of routing information from the UDM for the transfer of short messages (used by SMS-Router, IP-SM-GW, etc.).
  • No SBI-based interface is defined for MO / MT SMS from or to IP-SM-GW/SMS Router or any other NF that may want to send/receive SMS via interactions with SMSF.
  • MAP and/or Diameter have to be supported by the SMSF and the UDM in order to fully support 5G SMSoNAS. It is hence not possible to deploy a pure SBI-based 5GC if SMS has to be supported.
  • In the roaming scenarios, MO and MT SMS cannot benefit from the new inter-PLMN 5GC security framework based on the SEPP and the use of the secured N32 interface, relying instead on legacy MAP and/or Diameter SMS interfaces with all the well-known security vulnerabilities.
This Technical Report aims to study the key issues and requirements for implementing SBA/SBI paradigm and associated enhancements for 5G SMS and potential solutions to resolve the identified issues.

1  Scopep. 8

The present document identifies the SMS transfer in 5G network based on service-based interfaces, which allow SMSF and UDM to only support the SBI based interfaces in 5GC and avoid resorting to legacy MAP and Diameter interfaces within the PLMN and across PLMNs including roaming scenarios, identifies the key issues that are related to support of Service-based interfaces in 5GC, analyses potential solutions to address the key issues.

2  Referencesp. 8

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 23.040: "Technical realization of the Short Message Service (SMS)".
TS 23.501: "System architecture for the 5G System (5GS); Stage 2".
TS 23.502: "Procedures for the 5G System (5GS); Stage 2".
TS 23.632: "User data interworking, coexistence and migration; Stage 2".
TS 29.540: "5G System; SMS Services; Stage 3".
TS 29.503: "5G System; Unified Data Management Services; Stage 3".
TS 24.011: "Point-to-Point (PP) Short Message Service (SMS) support on mobile radio interface".
TS 29.573: "5G System; Public Land Mobile Network (PLMN) Interconnection; Stage 3".
TS 29.510: "5G System; Network Function Repository Services; Stage 3".

3  Definitions of terms, symbols and abbreviationsp. 8

3.1  Termsp. 8

For the purposes of the present document, the terms 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.
alert SC:
service element provided by a GSM/UMTS/EPS/5GS PLMN to inform an SC which has previously initiated unsuccessful short message delivery attempt(s) to a specific MS/UE, that the MS/UE is now recognized by the PLMN to have recovered operation.
Gateway MSC For Short Message Service (SMS GMSC):
function of an MSC capable of receiving a short message from an SC, interrogating an HLR/HSS/UDM for routing information and SMS info, and delivering the short message to the VMSC/SGSN/MME/SMSF of the recipient MS/UE.
Interworking MSC For Short Message Service (SMS IWMSC):
function of an MSC capable of receiving a short message from within the PLMN and submitting it to the recipient SC.
IP-Short-Message-Gateway (IP-SM-GW):
function responsible for protocol interworking between the IP-based UE and the SC.
Service Centre (SC):
function responsible for the relaying and store and forwarding of a short message between an SME and an MS/UE.

3.2  Symbolsp. 9

For the purposes of the present document, the following symbols apply:

3.3  Abbreviationsp. 9

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.
Generic Public Subscription Identifier
Mobile Originated Short Message Service
Mobile Terminated Short Message Service
Number Portability
Network Repository Function
Service Based Architecture
Service Based Interface
Short Message Service
Short Message Mobile Originated
Short Message Mobile Terminated
Short Message Service Function
SMS over NAS
Unified Data Management

4  Overall Requirementsp. 9

In order to remove dependency of legacy MAP and Diameter interfaces from SMSF and UDM for SMS service, following requirements shall be considered during the study:
  • A full SBI based solution for SMS service in 5GC shall be specified;
  • Routing mechanism for SMS delivery shall be based on service-based interfaces between 5GC and legacy SMS nodes (e.g. SMS-Router, IP-SM-GW, etc.);
  • The candidate solutions shall be applicable for roaming and non-roaming scenarios;
  • SMS delivery for MSISDN-less terminals (e.g. CIoT terminals) shall be supported.

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