Non-Integrated Non-3GPP Access

Description

Non-Integrated Non-3GPP Access is a 5G core network access type introduced in 3GPP Release 19. Unlike traditional non-3GPP access methods such as untrusted non-3GPP access (which requires a Non-3GPP InterWorking Function, N3IWF) or trusted non-3GPP access (which requires a Trusted Non-3GPP Gateway Function, TNGF), this access type eliminates the need for any intermediate network function between the User Equipment (UE) and the User Plane Function (UPF). The UE establishes direct IP connectivity to the UPF over the non-3GPP access network, which can be any IP-based network such as Wi-Fi, wired broadband, or satellite. This direct connection allows UE data flows to be routed to operator services without traversing additional gateways, thereby reducing latency, simplifying the network architecture, and lowering deployment costs.

Architecturally, Non-Integrated Non-3GPP Access integrates with the 5G Core (5GC) through the N3 interface between the non-3GPP access network and the UPF, or via a direct IPsec tunnel between the UE and the UPF. The control plane signaling for session management, authentication, and mobility is handled by the Access and Mobility Management Function (AMF) and Session Management Function (SMF) over the N1 and N2 interfaces, but the user plane bypasses any non-3GPP interworking function. The UE must support the necessary protocols to establish a PDU session over this access, including NAS signaling over non-3GPP access and IPsec for secure tunneling if required. The UPF acts as the anchor point for the PDU session, enforcing policy rules and forwarding traffic to the Data Network (DN).

Key components include the UE, the non-3GPP access network (which only provides IP transport), the UPF, and the 5GC control plane functions (AMF, SMF, PCF, UDM). The UE initiates a PDU session establishment request over the non-3GPP access, which is sent via the AMF to the SMF. The SMF selects an appropriate UPF and establishes the user plane path directly between the UE and the UPF. Security is provided by IPsec or other mechanisms as specified in 3GPP TS 33.754, ensuring confidentiality and integrity of user data. The non-3GPP access network does not need to support any 3GPP-specific interfaces or protocols beyond IP transport, making it access-agnostic.

This access type is particularly relevant for scenarios where the non-3GPP access network is trusted or where the operator wants to minimize the complexity of interworking functions. It enables new business models, such as fixed-mobile convergence, where a UE can seamlessly connect via a fixed broadband network directly to the 5G core. It also supports low-latency applications by avoiding the extra hop through an N3IWF or TNGF. However, it requires that the non-3GPP access network provides a sufficiently secure IP path and that the UE and UPF support the necessary protocols for direct connectivity.

In summary, Non-Integrated Non-3GPP Access represents a streamlined approach to integrating non-3GPP access into the 5G core, reducing architectural complexity and improving performance. It is a key enabler for operators to leverage any IP access network while maintaining a consistent service experience and adhering to 3GPP security and QoS frameworks.

Purpose & Motivation

Non-Integrated Non-3GPP Access was created to address the limitations of existing non-3GPP access integration methods, which require dedicated interworking functions like N3IWF or TNGF. These functions add complexity, cost, and latency to the network, as all user plane traffic must traverse them. For operators seeking to integrate non-3GPP access networks (e.g., Wi-Fi, fixed broadband) more efficiently, these intermediate nodes represent a bottleneck and a significant deployment burden. The new access type eliminates these nodes by enabling direct IP connectivity between the UE and the UPF, simplifying the architecture and reducing the number of network elements to manage.

Historically, 3GPP defined untrusted non-3GPP access (via N3IWF) in Release 15 and trusted non-3GPP access (via TNGF) in Release 16. While these solutions provided secure access over non-3GPP networks, they introduced additional signaling and user plane processing. The N3IWF and TNGF act as gateways that terminate IPsec tunnels from the UE and relay traffic to the UPF over N3. This indirection increases latency and requires operators to deploy and scale these functions. Non-Integrated Non-3GPP Access, introduced in Release 19, removes this indirection by allowing the UE to connect directly to the UPF, provided the non-3GPP access network is capable of transporting IP packets securely. This is particularly beneficial for trusted networks where the operator has control or a high degree of trust.

The motivation also includes supporting new use cases such as fixed wireless access, where a UE (e.g., a residential gateway) connects via a fixed network directly to the 5G core without the need for a TNGF. This reduces capital and operational expenditures for operators and simplifies the integration of non-3GPP access into the 5G ecosystem. Furthermore, it aligns with the broader 3GPP goal of access-agnostic core networks, where the core can serve UEs over any access technology with minimal access-specific adaptations.