Description
Non-3GPP QoS Assistance Information (N3QAI) is a concept introduced in 3GPP Release 18 to enhance Quality of Service (QoS) handling for User Equipment (UE) connected via untrusted non-3GPP access, such as Wi-Fi, through the Non-3GPP InterWorking Function (N3IWF). In a pure 3GPP access scenario, the Radio Access Network (RAN) is fully aware of 5G QoS Flows and can map them to appropriate radio bearers. However, when a UE uses a non-3GPP access like Wi-Fi, the underlying access network is typically unaware of 5G QoS constructs. The N3QAI mechanism allows the UE to provide hints to the 5G Core about the QoS characteristics of its uplink traffic, enabling better QoS enforcement at the N3IWF and beyond.
The N3QAI is information sent by the UE, typically as part of the uplink user plane data transmission or via associated control signaling when establishing a PDU session or QoS Flow over non-3GPP access. This information includes parameters that describe the QoS requirements of the application data being sent. These parameters can mirror or derive from 5G QoS characteristics, such as 5G QoS Identifier (5QI), Allocation and Retention Priority (ARP), Guaranteed Flow Bit Rate (GFBR), Maximum Flow Bit Rate (MFBR), or other traffic descriptors. The UE's application layer or its QoS management layer generates this assistance information based on the service requirements.
Upon receiving packets marked with N3QAI from the UE over the NWu IPsec tunnel, the N3IWF can utilize this information. The primary role of the N3IWF is to interpret the N3QAI and perform two key functions: first, to map the incoming traffic to the appropriate 5G QoS Flow within the existing PDU session for the N3 interface towards the UPF; second, to potentially apply local QoS policies or markings on the traffic before forwarding it. This assists the 5G Core's Session Management Function (SMF) and Policy Control Function (PCF) in enforcing the correct QoS policies end-to-end, even though the non-3GPP access segment itself cannot natively support 5G QoS signaling.
Architecturally, N3QAI operates within the user plane path between the UE and the N3IWF. It is a form of QoS signaling that complements the standard N1 NAS signaling used for QoS Flow establishment. Its introduction acknowledges that in many non-3GPP deployments, especially Wi-Fi, the last-hop link characteristics (e.g., Wi-Fi channel conditions, congestion) are opaque to the 5G Core. By providing assistance information from the UE—the endpoint experiencing the local access conditions—the network can make more informed decisions on traffic prioritization and resource allocation, improving the overall consistency of the quality of experience for services like voice, video, or gaming when accessed via Wi-Fi.
Purpose & Motivation
N3QAI was created to address a significant gap in the 5G QoS framework when applied to untrusted non-3GPP access networks. The core problem is the asymmetry of QoS awareness: while the 5G Core defines precise QoS Flows with specific parameters, the non-3GPP access network (e.g., a commercial or residential Wi-Fi router) has no understanding of these 5G-specific constructs. Prior to N3QAI, QoS enforcement for traffic from a UE over non-3GPP access relied heavily on static policies configured at the N3IWF or deep packet inspection (DPI), which could be inefficient, inaccurate, or not dynamically aligned with application needs.
The motivation for N3QAI stems from the increasing reliance on Wi-Fi for delivering high-quality 5G services, especially in indoor and fixed-wireless convergence scenarios. Without a mechanism for the UE to communicate its real-time QoS needs, the network might treat all traffic from a Wi-Fi connection with a default, potentially low-priority QoS profile, degrading the performance of latency-sensitive or high-bandwidth applications. N3QAI solves this by allowing the UE, which has the best knowledge of the application's requirements, to explicitly signal these requirements to the interworking function.
Historically, similar concepts existed in limited forms (like DSCP marking over IPsec), but they were not standardized within the 3GPP architecture for non-3GPP access. N3QAI provides a standardized, 3GPP-aligned method for QoS assistance. It enables more dynamic and accurate QoS mapping, which is essential for supporting advanced 5G services like network slicing, Ultra-Reliable Low Latency Communications (URLLC), and enhanced Mobile Broadband (eMBB) over converged access networks. It represents an evolution from network-centric QoS assumption to a more collaborative, end-point-assisted QoS model for heterogeneous access.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (530 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the Non-3GPP QoS Assistance Information (N3QAI) function was introduced as a new set of QoS assistance information provided to the UE to support QoS mechanisms over non-3GPP access networks like untrusted WLAN. This introduction was part of the broader architectural work to integrate non-3GPP access, such as via the N3IWF, with the 5G Core Network using the N2 and N3 interfaces. The enhancements, including clarifications on CN assistance information, provided a foundation for managing QoS for PDU Sessions established over these access types.
- Establishment of N1 NAS signalling connection due to change in the network slicing information TS 24.501CR0169
- Interworking between E-UTRAN/EPC and N3IWF/5GCN TS 24.501CR0176
- Configuration information the UE may exchange with the SMF during the lifetime of a PDU Session TS 23.501CR0003
- Correction to handling of S-NSSAI mapping information TS 23.501CR0020
- Update on Traffic Detection Information TS 23.501CR0026
- Traffic mapping information that disallows UL packets TS 23.501CR0053
+ 25 more changes
In Release 16, the N3QAI (Non-3GPP QoS Assistance Information) function was introduced as a new set of QoS assistance information provided to the UE. This was part of the broader enhancements for non-3GPP access integration, including support for the N3IWF and TNGF entities connecting to the 5G Core Network via the N2 and N3 interfaces. The release also specified related procedures for N3IWF selection and the establishment of IPsec tunnels for non-3GPP access registration.
- Introduction of ATSSS Support TS 23.501CR0735
- Support of Steering Functions for ATSSS TS 23.501CR0740
- Description of solution 2 in 23.725 for redundancy as an informational annex TS 23.501CR0754
- ATSSS-SMF and UPF selection TS 23.501CR0761
- Updating 5.8.2.11 for N4 Rules to support ATSSS TS 23.501CR0785
- FQDN format of N3IWF in a standalone non-public network TS 23.501CR0841
+ 111 more changes
In Release 17, the N3QAI (Non-3GPP QoS Assistance Information) function was introduced as a defined set of QoS assistance information provided to the UE. This addition was part of broader enhancements for non-3GPP access, which included updates to N3IWF selection procedures and the support for establishing IPsec tunnels with the N3IWF or TNGF for 5G Core Network registration.
- Informative guideline on supporting session/service continuity between SNPN and PLMN when using N3IWF TS 23.501CR2563
- Applying thresholds to Load-Balancing steering mode in ATSSS TS 23.501CR2590
- KI#3A - TSC Assistance container determined by NEF TS 23.501CR2619
- Service Assistance Information for 3GPP Advanced Interactive Service TS 23.501CR2653
- Update to N3IWF selection for N3SLICE TS 23.501CR2662
- PMF extensions for sending UE-assistance data to UPF TS 23.501CR2647
+ 103 more changes
In Release 18, the N3QAI (Non-3GPP QoS Assistance Information) function was enhanced to support UE and network procedures for **slice-based N3IWF selection**. Key new capabilities included allowing the UE to indicate its support for this selection to the network, and enabling the network to reject or abort a UE registration if the selected N3IWF is not compatible with the UE's allowed or requested Network Slice Selection Assistance Information (S-NSSAI).
- N3IWF selection enhancement for support of S-NSSAI needed by UE TS 23.501CR3707
- Introduction of 5GS Information Exposure TS 23.501CR3887
- Assistance to Member Selection Functionality for Application Operation TS 23.501CR3910
- 5GS Assistance for Application AI/ML operation: General clause TS 23.501CR3968
- SNPN broadcast system information and manual network selection for localized service TS 23.501CR4095
- Delivery of Traffic Influence information for Home Routed-Session Breakout (HR-SBO) support TS 23.501CR4160
+ 160 more changes
In Release 19, the enhancements for Non-3GPP QoS Assistance Information (N3QAI) specifically introduced the capability for leveraging PDU Set QoS information for DSCP marking over the N3 and N9 interfaces within the transport network. This was complemented by the new support for PDU Set Information Identification for end-to-end encrypted traffic using connect-UDP, as detailed in the architectural specifications. Furthermore, the release added a "PDU Set Information Marking Support Indication" to signal and utilize these QoS assistance mechanisms.
- Adding the NAT information exposure and Packet Inspection functionality in the UPF NF profile TS 23.501CR5420
- Introduction of new network function for energy related information, its definition and corresponding Architecture Reference Model TS 23.501CR5636
- General description of relaying media related information over N6 using an encapsulation protocol TS 23.501CR5711
- Support PDU Set information identification based on MoQ for encrypted XRM traffic TS 23.501CR5632
- PDU Set Information Identification for end-to-end encrypted traffic using connect-UDP - architecture part TS 23.501CR5728
- KI#3: Enhancement for AF influence on traffic routing with Energy related information TS 23.501CR5713
+ 98 more changes
In Release 20, the N3QAI (Non-3GPP QoS Assistance Information) function was enhanced with the introduction of the Energy Information Function (EIF), which exposes new energy-related data. This includes energy consumption information for policy control and per-UE application ranking information provided by the EIF. Furthermore, this energy-related information is utilized for procedures such as N3IWF/TNGF reselection to optimize network resource usage.
Explore further
Broader topics and technologies where N3QAI plays a role.
Defining Specifications
3GPP specifications that define or reference N3QAI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 29.502 vj50 | 5G System; Nsmf Service Based Interface; Stage 3 | Rel-19 |