Overview

Service Management and Exposure has 2 components - Service Manager and CAPIF Core . Service Manager is in the “servicemanager” directory. Capifcore is found in the “capifcore” directory.

This product is a part of NONRTRIC.

Service Manager

Service Manager Overview

Service Manager implements the R1 interface by providing a wrapper for R1 APIs that are produced and/or consumed by rApps. Service Manager also provides a wrapper for the Kong API Gateway.

If an rApp app needs access to a published service, it needs to go through Service Manager. It cannot access the published service directly.

Service Manager and the R1 API

CAPIF stands for Common API Framework and it was developed by 3GPP to enable a unified Northbound API framework across 3GPP network functions, and to ensure that there is a single and harmonized approach for API development. CAPIF (Common API Framework) is defined in 3GPP TS 29.222. Among CAPIF’s key features are the following.

• Register/deregister APIs

• Publishing Service APIs

• Onboarding/offboarding API invoker

• Discovery APIs

• CAPIF events subscription/notification

• Entity authentication/authorization

• Support for 3rd party domains i.e., allow 3rd party API providers to leverage the CAPIF framework

• Support interconnection between two CAPIF providers

Service Manager wraps CAPIF to provide the following Northbound service APIs.

• Register/deregister APIs

• Publishing Service APIs

• Onboarding/offboarding API invoker

• Discovery APIs

If you only need the above APIs, then Service Manager is a plugin-in replacement for CAPIF.

CAPIF APIs wrapped by Service Manager

• CAPIF_API_Provider_Management API: This API enables the API Management Function to communicate with the CAPIF core function to register the API provider domain functions.

• CAPIF_Publish_Service_API API:This API enables the API publishing function to communicate with the CAPIF core function to publish the service API information and manage the published service API information.

• CAPIF_API_Invoker_Management API: This API enables the API invoker to communicate with the CAPIF core function to enroll as a registered user of CAPIF and manage the enrollment information.

• CAPIF_Discover_Service_API API: This API enables the API invoker to communicate with the CAPIF core function to discover the published service API information.

Service Name	Service Operations	Operation Semantics	Consumer(s)
CAPIF_API_Provider_Management_API	Register_API_Provider	POST /registrations	API Management Function
	Update_API_Provider	PUT /registrations/{registrationId}	API Management Function
	Deregister_API_Provider	DELETE /registrations/{registrationId}	API Management Function
CAPIF_Publish_Service_API	Publish_Service_API	POST /{apfId}/service-apis	API Publishing Function, CAPIF core function
	Unpublish_Service_API	DELETE /{apfId/service-apis/{serviceApiId}	API Publishing Function, CAPIF core function
	Update_Service_API	PUT /{apfId/service-apis/{serviceApiId}	API Publishing Function, CAPIF core function
	Get_Service_API	GET /{apfId}/service-apis	API Publishing Function, CAPIF core function
CAPIF_API_Invoker_Management_API	Onboard_API_Invoker	POST /onboardedInvokers	API Invoker
	Offboard_API_Invoker	DELETE /onboardedInvokers/{onboardingId}	API Invoker
	Notify_Onboarding_Completion	Subscribe/Notify	API Invoker
	Update_API_Invoker_Details	PUT /onboardedInvokers/{onboardingId}	API Invoker
	Notify_Update_Completion	Subscribe/Notify	API Invoker
CAPIF_Discover_Service_API	Discover_Service_API	GET /allServiceAPIs	API Invoker, CAPIF core function

Generation of OpenAPI Code

• The R1 APIs are generated from the OpenAPI specifications provided by 3GPP.

• The generate.sh script downloads the specifications from 3GPP, fixes them and then generates the northbound APIs.

• The specifications are downloaded from https://www.3gpp.org/ftp/Specs/archive/29_series.

• CAPIF needs the server implementation while Service Manager needs both server and client implementations. Service Manager needs the client to access CAPIF and the server to provide access to the rApps.

Service Manager Integration with Kong

• Service Manager is a Go implementation of a service that wraps both CAPIF and Kong.

• When publishing a service through Service Manager, we create a Kong service and Kong route.

• The JSON element that we return in the response body is updated to point to the Kong data plane. Therefore, the API interface that we return from Service Discovery has the Kong host and port, and not the original service’s host and port.

• The rApp can only access the Published function through Service Manager. It cannot access the Published function directly.

• We use Kong as a reverse proxy. Instead of calling the Publishing service directly, our Invoker’s API request is proxied through Kong. This gives us the advantages of using a proxied service, such as providing caching and load balancing.

• When service invocations are routed through Kong, in an R1 SME scenario where services are selectively exposed to rApps, the Kong API gateway can be used to enforce R1 SME exposure and access.

• Service exposure is achieved by restricting rApps to have access only to the Kong API gateway, and so only services exposed to the rApps through the API gateway can be accessed.

Service Manager Deployment

• We have a stand-alone deployment and a deployment as part of NONRTRIC.

• We use the NONRTRIC deployment from the Git repo at https://gerrit.o-ran-sc.org/r/admin/repos/it/dep.

• The stand-alone deployment is in this repo at sme/servicemanager/deploy. Please see the Service Manager README.

• The Service Manager configuration is stored in a config file, .env.

• For both the stand-alone and it/dep deployments, .env is volume-mounted into the Docker container from a Kubernetes config map at container run-time.

Postman

A Postman collection has been included in this repo at sme/postman/ServiceManager.postman_collection.json.

CAPIF

Introduction

CAPIF stands for Common API Framework and it was developed by 3GPP to enable a unified Northbound API framework across 3GPP network functions, and to ensure that there is a single and harmonized approach for API development.

Key features in CAPIF includes onboarding and offloading of application functions, service discovery and management, event subscription and notification as well as authorization and authentication.

It was delivered in Rel-15 (Refer to 3GPP TS 23.222 and 3GPP TS 29.222).

Functional entities

The CAPIF consists of an API provider functions, the CAPIF core functions and API Invoker.

CAPIF Core function

The CAPIF core functions support the API invokers to access the service APIs. It consists of the following capabilities:

• Authenticating the API invoker based on the identity and other information required for authentication of the API invoker;

• Supporting mutual authentication with the API invoker;

• Providing authorization for the API invoker prior to accessing the service API;

• Publishing, storing and supporting the discovery of service APIs information;

• Monitoring the service API invocations;

• Onboarding a new API invoker and offboarding an API invoker;

• Supports publishing, discovery of service APIs information with another CAPIF core function in CAPIF interconnection.

API Invoker

The API invoker is the entity which invokes the CAPIF or service APIs, typically provided by a 3rd party application provider.

The API invoker supports the following capabilities:

• Triggering API invoker onboarding/offboarding;

• Supporting the authentication by providing the API invoker identity and other information required for authentication of the API invoker;

• Supporting mutual authentication with CAPIF;

• Obtaining the authorization prior to accessing the service API;

• Discovering service APIs information; and

• Invoking the service APIs.

API Provider functions

The API provider functions consists of:

• API exposing function is the provider of the service APIs and is also the service communication entry point of the service API to the API invokers. Provides access control, logging, charging, provides authentication and authorization support.

• API publishing function is responsible for the capability to publish the service API information of the API provider to the CAPIF core functions in order to enable the discovery of APIs by the API invoker.

• API management function is the entity which registers and maintains registration information of the API provider domain functions on the CAPIF core function.

CAPIF core function APIs

• CAPIF_Discover_Service_API API: This API enables the API invoker to communicate with the CAPIF core function to discover the published service API information.

• CAPIF_Publish_Service_API API: This API enables the API publishing function to communicate with the CAPIF core function to publish the service API information and manage the published service API information.

• CAPIF_Events API: This API enables the API subscribing entity to communicate with the CAPIF core function to subscribe to and unsubscribe from CAPIF events and receive subsequent notification of CAPIF events. This API is used for the subscription to and notifications of those CAPIF events that are not bound to any of the other CAPIF core function APIs.

• CAPIF_API_Invoker_Management API: This API enables the API invoker to communicate with the CAPIF core function to enroll as a registered user of CAPIF and manage the enrollment information.

• CAPIF_Security API:This API enables the API invoker to communicate with the CAPIF core function to authenticate and obtain authorization to access service APIs.

• CAPIF_Monitoring API: This API enables the API management function to communicate with the CAPIF core function to subscribe to and unsubscribe from CAPIF events related to monitoring and receive subsequent notification of CAPIF monitoring events.

• CAPIF_Logging_API_Invocation API: This API enables the API exposing function to communicate with the CAPIF core function to log the information related to service API invocation.

• CAPIF_Auditing API: This API enables the API management function to communicate with the CAPIF core function to retrieve the log information related to service API invocation.

• CAPIF_Access_Control_Policy API: This API enables the API exposing function to obtain the policy to perform access control on the service API invocations.

• CAPIF_Routing_Info API: This API enables the API exposing function to obtain the routing information to forward the API invocation to another API exposing function.

• CAPIF_API_Provider_Management API: This API enables the API Management Function to communicate with the CAPIF core function to register the API provider domain functions as authorized users of the CAPIF functionalities.

The table below lists the CAPIF Core Function APIs.

Service Name	Service Operations	Operation Semantics	Consumer(s)
CAPIF_Discover_Service_API	Discover_Service_API	GET /allServiceAPIs	API Invoker, CAPIF core function
CAPIF_Publish_Service_API	Publish_Service_API	POST /{apfId}/service-apis	API Publishing Function, CAPIF core function
	Unpublish_Service_API	DELETE /{apfId/service-apis/{serviceApiId}	API Publishing Function, CAPIF core function
	Update_Service_API	PUT /{apfId/service-apis/{serviceApiId}	API Publishing Function, CAPIF core function
	Get_Service_API	GET /{apfId}/service-apis	API Publishing Function, CAPIF core function
CAPIF_Events_API	Subscribe_Event	Subscribe/Notify	API Invoker, API Publishing Function, API Management Function, API Exposing Function
	Notify_Event	Subscribe/Notify	API Invoker, API Publishing Function, API Management Function, API Exposing Function
	Unsubscribe_Event	Subscribe/Notify	API Invoker, API Publishing Function, API Management Function, API Exposing Function
CAPIF_API_Invoker_Management_API	Onboard_API_Invoker	POST /onboardedInvokers	API Invoker
	Offboard_API_Invoker	DELETE /onboardedInvokers/{onboardingId}	API Invoker
	Notify_Onboarding_Completion	Subscribe/Notify	API Invoker
	Update_API_Invoker_Details	PUT /onboardedInvokers/{onboardingId}	API Invoker
	Notify_Update_Completion	Subscribe/Notify	API Invoker
CAPIF_Security_API	Obtain_Security_Method	PUT /trustedInvokers/{apiInvokerId}	API Invoker
	Obtain_Authorization	POST /securities/{securityId}/token	API Invoker
	Obtain_API_Invoker_Info	GET /trustedInvokers/{apiInvokerId}	API exposing function
	Revoke_Authorization	DELETE /trustedInvokers/{apiInvokerId}	API exposing function
CAPIF_API_Provider_Management_API	Register_API_Provider	POST /registrations	API Management Function
	Update_API_Provider	PUT /registrations/{registrationId}	API Management Function
	Deregister_API_Provider	DELETE /registrations/{registrationId}	API Management Function
CAPIF_Monitoring_API	Event operations		API Management Function
CAPIF_Logging_API_Invocation_API	Log_API_Invocation	POST /{aefId}/logs	API exposing function
CAPIF_Auditing_API	Query_API_Invocation_Log	GET /apiInvocationLogs	API management function
CAPIF_Access_Control_Policy_API	Obtain_Access_Control_Policy	GET /accessControlPolicyList/{serviceApiId}	API Exposing Function
CAPIF_Routing_Info_API	Obtain_Routing_Info	GET /service-apis/{serviceApiId}	API exposing function

Security in CAPIF

CAPIF establishes security requirements for all the interfaces defined in the specification. There are also security requirements that are applicable to all CAPIF entities, such as:

• CAPIF shall provide mechanisms to hide the topology of the PLMN trust domain from the API invokers accessing the service APIs from outside the PLMN trust domain.

• CAPIF shall provide mechanisms to hide the topology of the 3rd party API provider trust domain from the API invokers accessing the service APIs from outside the 3rd party API provider trust domain.

• CAPIF shall provide authorization mechanism for service APIs from the 3rd party API providers.

• CAPIF shall support a common security mechanism for all API implementations to provide confidentiality and integrity protection.

The image below shows the functional security model for CAPIF architecture. CAPIF-1, CAPIF-2, CAPIF-3, CAPIF-4, CAPIF-5 and CAPIF-7 are interfaces that lie within the PLMN trust domain while the CAPIF-1e , CAPIF-2e, CAPIF-3e, CAPIF-4e, CAPIF-5e and CAPIF-7e interfaces are CAPIF core and AEF access points for API Invokers outside of the PLMN trust domain.

Authentication and authorization are required for both API invokers that lie within the PLMN trust domain and API invokers that lie outside of the PLMN trust domain. For an API invoker that is outside of the PLMN trust domain, the CAPIF core function in coordination with the API exposing function utilizes the CAPIF-1e, CAPIF-2e and the CAPIF-3 interfaces to onboard, authenticate and authorize the API invoker prior to granting access to CAPIF services.

Security procedures for API invoker onboarding

The API invoker and the CAPIF core function shall establish a secure session. With a secure session established, the API Invoker sends an Onboard API Invoker Request message to the CAPIF core function. The Onboard API Invoker Request message carries an onboard credential obtained during pre-provisioning of the onboard enrolment information.

The CAPIF core function shall respond with an Onboard API invoker response message. The response shall include the CAPIF core function assigned API invoker ID, API invoker’s certificate and the API invoker Onboard_Secret (generated by the CAPIF core function provided by keycloak).

Security method negotiation

The API invoker and the CAPIF core function shall negotiate a security method that shall be used by the API invoker and the API exposing function for CAPIF-2e interface authentication and protection.

As a pre-condition the API invoker must be onboarded with the CAPIF core function.

After successful mutual authentication on CAPIF-1e interface, the API invoker may send CAPIF-2/2e security capability information to the CAPIF core function in the Security Method Request message, indicating the list of security methods that it supports for each AEF.

The CAPIF core function shall select a security method to be used over CAPIF-2/2e reference point for each requested AEF, taking into account the information sent by the API invoker and send a Security Method Response message to the API invoker indicating the selected security method for each AEF.

API discovery

After successful authentication between API invoker and CAPIF core function, the CAPIF core function shall decide whether the API invoker is authorized to perform discovery based on API invoker ID and discovery policy.

Postman

A Postman collection has been included in this repo at sme/postman/CAPIF.postman_collection.json.