Untrusted Non-3GPP Access

Untrusted Non-3GPP Access (UNAA) is a 3GPP-defined method for connecting devices to a 5G Core Network (5GC) over external IP-based access systems, such as Wi-Fi, that the mobile network does not administratively control or trust at Layer 2.

Expanded Explanation

1. Technical Function and Core Characteristics

UNAA allows User Equipment (UE) to reach 5GC functions through access networks like Wi-Fi or other IP access that do not implement 3rd Generation Partnership Project (3GPP) security and control mechanisms. The model treats the external access as untrusted and relies on secure tunneling and authentication at higher layers.

3GPP specifications define dedicated core functions for this scenario, such as the Non-3GPP Interworking Function and the N3IWF reference point architecture. These functions establish IPsec tunnels, perform authentication, and apply policy so that traffic from untrusted access aligns with 5G core requirements.

2. Enterprise Usage and Architectural Context

Enterprises use UNAA to extend 5G core-based services over existing Wi-Fi or fixed access networks without integrating those access networks into the 3GPP trust and control domain. This enables connectivity for private 5G deployments, campus networks, and remote users through third-party or on-premises (on-prem) IP access.

Architecturally, the enterprise environment connects the untrusted access network to the operator or private 5G core through secure gateways that implement N3IWF-like capabilities. Policy control, user authentication, and Quality of Service (QoS) enforcement remain in the 5G core, while the non-3GPP access provides only IP connectivity.

3. Related or Adjacent Technologies

Related concepts include Trusted Non-3GPP Access (TNAA), where the non-3GPP network meets 3GPP trust and security requirements and uses interfaces such as TNGF and TWAG. UNAA also relates to Wi-Fi offload, access traffic steering, switching and splitting, and IPsec-based remote access.

Standards bodies such as 3GPP and ETSI describe how UNAA interworks with network functions like the Access and Mobility Management Function, Session Management Function, and Policy Control Function. These relationships define how sessions, mobility, and policy operate consistently across 3GPP and non-3GPP access types.

4. Business and Operational Significance

For enterprises and operators, UNAA provides a way to use existing Wi-Fi or fixed access infrastructure to reach a 5G core while centralizing security and policy in the core network. This supports use of 5G capabilities without requiring full 3GPP integration of every access domain.

Operationally, this model requires management of IPsec termination, authentication, and policy enforcement at the interworking function, along with monitoring of traffic from untrusted domains. It affects network design, roaming arrangements, and security architecture for private and public 5G deployments.