Application Programming Interface

In Release 15, the primary API introduction was the standardized Northbound API and the 5G service-based interface architecture, which defined new application interfaces for network functions like the AUSF and PCF. The release also focused on specifying detailed API information, security requirements for API invoker onboarding, and consistent API versioning management. Furthermore, it included corrections for application error codes and the presentation of API resources to ensure proper implementation.

• Introduce the Northbound API charging TS 32.240CR0394
• Introduction of 5G service based interface TS 32.240CR0398
• Security requirements for API invoker onboarding and offboarding TS 33.122CR0005
• Correction for the details of service API information TS 23.222CR0013
• Correction for usage of service API identification information TS 23.222CR0014
• Clause W.2 on "Architecture without IMS-level roaming interfaces" to refer to clause Y.9.2 that defines it for the 5GS case. TS 23.228CR1196

+ 17 more changes

In Release 16, the API function was enhanced to formally support multiple third-party API providers and CAPIF (Common API Framework) interconnection. New capabilities included requirements and procedures for API publishing, discovery, and registration involving multiple providers and CCFs (CAPIF Core Functions), along with specific charging and OAM requirements for these third parties. The release also introduced features for API invocation request routing with topology hiding and defined the serving area and domain for service APIs within the interconnected architecture.

• Architecture functional model to support multiple API providers TS 23.222CR0012
• Service API publish and discovery requirements for 3rd party API providers TS 23.222CR0015
• Charging requirements for 3rd party API providers TS 23.222CR0016
• OAM requirements for 3rd party API providers TS 23.222CR0017
• API publish and API discover for CAPIF interconnection TS 23.222CR0035
• Update API invoker API list TS 23.222CR0039

+ 51 more changes

In Release 17, API enhancements focused on expanding service-based interfaces for Network Data Analytics (NWDAF) and edge computing. New service APIs like Nnwdaf_DataManagement and Nnwdaf_MLModelProvision were introduced, along with analytics extensions for user data congestion, NF load, dispersion, and redundant transmission experience. Furthermore, APIs were extended to support edge applications by providing serving area and location information, and to enhance 5G Media Streaming (5GMS) via eMBMS.

• Serving area information for service APIs to support edge applications TS 23.222CR0067
• Support AEF location and API invoker interface for edge application TS 23.222CR0078
• [5MBP3] API Extensions for 5GMS via eMBMS TS 26.347CR0013
• Supporting xMB interface extensions for 5GMS via eMBMS TS 29.116CR0054
• Adding uplink buffering indication for Application Relocation TS 29.508CR0142
• Application Detection triggering for dynamic AM policy changes TS 29.512CR0752

+ 109 more changes

In Release 18, the API function introduced new capabilities including the Eees_EASDiscovery API for Edge Application Server selection support and the Eees_EASInformationProvisioning API definition. Enhancements were made to authorization procedures for API invokers and to service APIs with new information elements for Service KPI publication and status monitoring. Furthermore, updates were specified for bootstrap procedures and the exposure of application detection events.

• API invoker obtaining authorization from resource owner TS 23.222CR0093
• Reducing resource owner consent inquiry in a nested API invocation TS 23.222CR0095
• API invoker clarification TS 23.222CR0100
• New IE(Service KPI) in Service API publish request TS 23.222CR0102
• Service API status monitoring TS 23.222CR0111
• Binding information of DC Application with DC - 23.228 TS 23.228CR1266

+ 214 more changes

In Release 19, key API enhancements focused on the Common API Framework (CAPIF), introducing a split of the API invoker into distinct frontend and backend components and refining access control with finer granularity for service APIs. The release also added new capabilities for slice-based service API exposure and introduced mechanisms for resource owner consent upon service API invocation. Furthermore, it defined a new `Sdd_URLCCTransmissionConnection` API provided by the SDDM-S and supported multiplexing multiple data communication applications over a single SCTP connection.

• Slice-based service API exposure TS 23.222CR0131
• Update to API invoker Roles in CAPIF TS 23.222CR0202
• Finer granularity of access control for service API TS 23.222CR0206
• API invoker onboarding TS 23.222CR0214
• API invoker split into frontend and backend components TS 23.222CR0221
• Enhancement to API invoker Authorization with the Purpose of Data Processing TS 23.222CR0226

+ 214 more changes

In Release 20, the key new development for the API function was the introduction of a standardized **API exposure Reference architecture**. This framework defines a set of Application Programming Interface (API) classes for developing applications and for providing system services to those applications, establishing a structured foundation for application access to network service capability features.

• API exposure Reference architecture TS 23.700CR0003