Vertical Application Layer Server

Description

The VAL (Vertical Application Layer) server is a fundamental architectural component in 3GPP's framework for supporting vertical industry services, such as those in factories, ports, hospitals, and smart cities. It represents the server-side application function that delivers a specific VAL service to VAL users. In essence, the VAL server hosts the business logic and service-specific capabilities that enable vertical applications to leverage 3GPP network services. It is not a single monolithic entity but a generic term that can refer to various server functions tailored to different vertical domains (e.g., a video surveillance server, an AR/VR server, or a industrial control server). The VAL server communicates with the VAL client residing in the UE (User Equipment) and with the underlying 3GPP network functions to request and utilize network capabilities such as QoS, mobility, and location services.

Architecturally, the VAL server resides in the Application Layer, logically outside the 3GPP core network but connected via the VAL service provider's domain. It interacts with the 5G Core Network through the VAL service capabilities, often exposed via the Service Enabler Architecture for Verticals (SEAL) or similar enablers. For example, the VAL server may request specific QoS treatment from the 5G Core via the Policy Control Function (PCF) or use the Network Exposure Function (NEF) to access network APIs. The server also manages the lifecycle of VAL services, including session establishment, user authentication, and data processing. The 3GPP specification TS 23.434 defines the VAL service architecture and the roles of the VAL server and client, while TS 29.549 specifies the API interactions between the VAL server and the 3GPP core network.

How it works: When a VAL user (e.g., an operator of a factory robot) initiates a service, the VAL client in the UE communicates with the VAL server to establish a session. The VAL server authenticates the user, determines the required service parameters, and negotiates with the 3GPP network for appropriate resources. For instance, for a low-latency video stream, the VAL server may request a QoS flow with specific 5QI (5G QoS Identifier) from the PCF. The VAL server then processes data, performs any necessary application-level functions, and sends control commands or data back to the client. The server may also interact with other application servers or databases within the vertical domain.

Key components of the VAL server include the service logic, which implements the vertical-specific functionality; the communication module, which handles interactions with VAL clients and network functions; and the management module, which handles registration, authentication, and session management. The VAL server can be deployed on-premises (e.g., at the edge) or in the cloud, depending on latency and data privacy requirements. Edge deployment is often preferred for ultra-reliable low-latency communication (URLLC) services.

In the broader network context, the VAL server is a crucial enabler for 5G's expansion beyond consumer mobile broadband into vertical industries. It allows vertical service providers to focus on their application logic while relying on the 3GPP network for connectivity, QoS, and mobility. The generic definition allows for flexibility: different verticals can have different VAL servers, but they all follow the same architectural principles defined by 3GPP. This standardization ensures interoperability and reduces integration complexity. With Release 19, 3GPP further refined the VAL server concept, and it continues to evolve in Release 20 to support more advanced features like AI/ML integration and enhanced edge computing.

Purpose & Motivation

The VAL server exists to provide a standardized way for vertical industry applications to access and utilize 3GPP network capabilities. Before its introduction, vertical industries often had to develop proprietary interfaces to the network, leading to fragmentation, increased cost, and limited scalability. The VAL server abstraction solves this by defining a common server-side function that can request network services (e.g., QoS, location, group communication) through standardized APIs, regardless of the vertical domain. This allows a factory automation application and a smart city application to use the same underlying mechanisms to request low-latency connectivity or high-availability sessions.

Another motivation is the need to decouple vertical application logic from network specifics. Vertical service providers are experts in their domains but not necessarily in 3GPP protocols. The VAL server acts as an intermediary, translating vertical service requirements into 3GPP service requests. This separation of concerns enables faster innovation and deployment of vertical services. It also allows the 3GPP network to expose its capabilities in a controlled and secure manner, as the VAL server can be authenticated and authorized before accessing network APIs.

The concept was introduced in Release 19 as part of 3GPP's ongoing efforts to support the broader 5G ecosystem, particularly for enterprise and industrial use cases. It builds on earlier work on service enablers like SEAL (Service Enabler Architecture for Verticals) and EDGEAPP (Edge Applications). The VAL server is a key element in making 5G a platform for vertical industries, not just a connectivity provider. Its generic definition ensures it can be adapted to numerous verticals while maintaining a consistent architectural approach, which is essential for interoperability and widespread adoption.