Application Type

Description

Application type is a concept defined in 3GPP specifications 23.335 and 29.335, which pertain to the Service Layer architecture, particularly the Service Capability Exposure Function (SCEF) and related entities. The application type identifies the specific application or service that a Functional Entity (FE) is handling. For example, an HLR (Home Location Register) may handle a particular application, and its application type is derived from the name indicated by the FE. This allows the network to route requests to the appropriate FE based on the application type, ensuring that the correct service logic is applied.

In the Service Layer architecture, FEs are logical entities that provide specific functions. Each FE is associated with an application type, which is used for discovery and selection. When a service request is received, the network determines the required application type and selects an FE that supports it. The application type is typically represented as a string or an identifier that is unique within the service layer. It is derived from the name indicated by the FE, which may be a fully qualified domain name (FQDN) or a similar naming convention.

The application type is crucial for enabling service differentiation and efficient resource allocation. It allows the network to direct requests to the correct FE without hardcoding specific addresses. This is particularly important in virtualized and cloud-based environments where FEs can be instantiated dynamically. The application type also facilitates load balancing and failover, as multiple FEs can support the same application type.

Key components include the FE, the application type identifier, and the service layer discovery mechanisms. The FE registers its application type with a discovery service, which can then be queried by other entities. The application type is used in the Service Layer to route requests, such as in the SCEF or the Service Capability Server (SCS). It is also used in the context of the 5G Service Based Architecture (SBA), where Network Function (NF) types and service names play a similar role.

The definition of application type has remained unchanged across all releases from Rel-9 to Rel-19, indicating its stability and foundational role. It is a simple yet powerful concept that enables the service layer to be flexible and scalable. By abstracting the application from the physical FE, it allows the network to evolve without disrupting services.

Purpose & Motivation

The Application Type concept was introduced to address the need for dynamic service discovery and selection in the Service Layer. Before its introduction, network entities were often statically configured with addresses of specific servers, which was inflexible and difficult to manage in evolving networks. The application type provides a level of indirection, allowing the network to identify the required service without knowing the exact location of the FE.

It solves the problem of scalability and flexibility in service deployment. As networks move towards virtualization and cloud-native architectures, the ability to dynamically discover and select FEs based on application type becomes essential. It also enables multi-tenancy, where different applications can be hosted on the same infrastructure but remain logically separated by their application types.

The concept was motivated by the need to support a wide range of services, from traditional telephony to IoT and M2M, each with different requirements. By using application types, the network can apply appropriate policies, QoS, and security measures. It also simplifies the integration of third-party applications, as they can register their application types and be discovered by the network.