Open Service Access Internal API

Description

The OSA Internal API is a standardised interface defined by 3GPP that facilitates communication between the OSA framework and service capability servers (SCSs) within the Open Service Access (OSA) architecture. It was introduced in Release 4 as part of the ongoing evolution of OSA, which began in Release 99. The OSA Internal API is distinct from the OSA Interface (also known as the OSA API) that applications use to access the framework; instead, it is an internal interface used by the framework to interact with the SCSs that implement specific service capabilities.

In the OSA architecture, the framework acts as a central point for authentication, authorisation, service discovery, and service invocation. When an application requests a service capability (e.g., call control, messaging, location), the framework authenticates the request and then uses the OSA Internal API to invoke the corresponding service on the appropriate SCS. The SCS then interacts with the underlying network elements to fulfil the request. The OSA Internal API defines the methods, parameters, and data structures that the framework uses to communicate with the SCSs.

The OSA Internal API is typically specified using object-oriented techniques, similar to the OSA Interface. It may be implemented using technologies such as CORBA, Java RMI, or web services. The API ensures that the framework can manage multiple SCSs from different vendors in a consistent manner, providing a standardised way to integrate new service capabilities into the OSA environment.

One of the key roles of the OSA Internal API is to enable the framework to perform its mediation functions. For example, the framework may need to translate between different data formats or protocols used by the application and the SCS. The OSA Internal API provides a common language for these interactions, reducing the complexity of integrating diverse service capabilities. It also supports the dynamic discovery of SCSs, allowing the framework to locate and invoke services as needed.

The OSA Internal API is specified in 3GPP technical specifications such as 23.127 (Virtual Home Environment/Open Service Access) and 23.198 (Open Service Access (OSA); Stage 2). While the OSA Internal API is not directly exposed to external applications, it is a critical component of the OSA architecture, ensuring that the framework can efficiently and securely manage service capability invocations. Its design reflects the principles of modularity, scalability, and interoperability that are central to OSA.

Purpose & Motivation

The OSA Internal API was created to provide a standardised mechanism for the OSA framework to communicate with service capability servers. In the early OSA architecture, the framework needed a consistent way to invoke services on behalf of applications, regardless of the underlying implementation of the SCSs. Without a standardised internal API, each SCS might require a proprietary interface, leading to integration challenges and limiting the ability to mix and match SCSs from different vendors.

The OSA Internal API solves this problem by defining a common set of interfaces and protocols that all SCSs must support. This allows the framework to manage multiple SCSs uniformly, simplifying the addition of new service capabilities and reducing the time and cost of integrating third-party services. It also enables network operators to deploy a multi-vendor OSA environment, fostering competition and innovation.

Furthermore, the OSA Internal API supports the separation of concerns between the framework and the SCSs. The framework handles authentication, authorisation, and service discovery, while the SCSs focus on implementing the service logic and interacting with network elements. This modular design enhances scalability and maintainability, as changes to one component do not necessarily affect the other. The OSA Internal API thus plays a crucial role in the overall OSA ecosystem, enabling the flexible and secure exposure of network capabilities.