Warning: 6G core network must not repeat the 5G SA 3GPP architecture specs vs lack of interoperable standards
Introduction:
As the global telecom ecosystem pivots from 5G/IMT 2020 towards normative studies for IMT-2030 (6G) in 3GPP Release 20 and Release 21, the air interface (IMT 2030 RIT/SRITs forthcoming recommendation) naturally commands the spotlight. Discussions are dominated by IMT 2030 Technical Performance Requirements like sub-millisecond latencies, Integrated Sensing and Communication (ISAC), and AI-native physical layers. Yet network architects must confront a sobering historical reality: a brilliant radio access network is utterly paralyzed without a functional, universally interoperable core network.
If the telecom industry intends to realize the true commercial and operational promises of 6G, we must urgently dismantle the architectural precedent set during the 5G Standalone (SA) core (lack of) standardization cycle. By bypassing traditional global transport gatekeepers and prioritizing abstract logical modeling over concrete implementation realities, the industry traded the promise of an open, multi-vendor cloud ecosystem for a return to legacy vendor lock-in.
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The ITU-T Bypass and the 5G SA Core Network Standardization Gap:
The fragmentation of the 5G SA core network can be traced directly to a structural and geopolitical power struggle.
- Historically, ITU-T Study Group 13 held the global mandate for establishing international standards for non-radio, architectural, and transport layers of all next generation networks. This governance ensured deep multi-vendor interconnectivity and data-plane uniformity across sovereign networks.
- During the development of the 5G Service-Based Architecture (SBA), 3GPP effectively insulated the core network design from ITU-T oversight. 3GPP executives told this author that they did not trust ITU-T to generate the 5G core network standards.
- Instead, the 3GPP specifications (such as TS 23.501 and TS 23.502) were kept entirely in-house and on completion were rubber-stamped by ETSI, 3GPP’s venue host. While this bypass accelerated time-to-market, it created a catastrophic standards-to-implementation gap. 3GPP defined network functions—such as the Access and Mobility Management Function (AMF), Session Management Function (SMF), and User Plane Function (UPF)—as highly abstract, logical blocks.
- While the control plane mandated modern tools like HTTP/2 and RESTful OpenAPIs, this framework merely established interface syntax. It completely omitted the exhaustive behavioral guardrails, edge-case definitions, and low-level realization mechanics required to build a production-ready, cloud-native core. That disconnect led to different network operator implementations of the 5G SA Core, depending on the vendor(s) they selected.
The Illusion of Interoperability:
The practical consequence of this abstraction is well known to any tier-1 network operator that has attempted a multi-vendor 5G SA core network deployment. On paper, the 5G SBA is modular. In reality, an operator cannot reliably procure an AMF from Vendor A, an SMF from Vendor B, and a UPF from Vendor C, connect them via standard 3GPP interfaces, and achieve a stable, carrier-grade network. The specifications are simply too loose.
Crucial underlying implementation details—such as cloud-native container orchestration pipelines, state database synchronization, database persistence layers, and hardware-accelerated UPF data planes—were left entirely outside the scope of the standard. To fill this vacuum, major infrastructure vendors engineered proprietary software logic beneath the “open” APIs. Consequently, multi-vendor core deployments required immense, custom, and cost-prohibitive systems integration efforts. For most operators, the path of least resistance was a return to single-vendor silos.
When 3GPP kept the Service-Based Architecture (SBA) work entirely in-house, they defined the network functions (like AMF, SMF, and UPF) as abstract, logical blocks rather than concrete blueprint specifications:
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- The Interface Gap: 3GPP dictated the use of HTTP/2 and RESTful OpenAPIs for the control plane. While that sounds open, it merely defined the syntax, not the exhaustive behavior required when edge cases or multi-vendor implementations collided.
- No Implementation Blueprint: Crucial components required to construct an actual, production-ready 5G SA core—such as cloud-native container orchestration pipelines, underlying state database synchronization, database persistence layers, and low-level User Plane Function (UPF) acceleration mechanics—were entirely omitted.
The Practical Outcome: A Return to Vendor Lock-In:
Because 3GPP’s architectural specs lacked concrete realization guidelines and strict inter-vendor edge-case definitions, a major interoperability gap emerged:
- Custom Customization: An operator cannot realistically buy an AMF from Vendor A, an SMF from Vendor B, and a UPF from Vendor C, plug them together over standard 3GPP interfaces, and expect a stable network. The specs are too loose.
- The “Joint Specification” Reality: In practice, every major 5G SA core deployed requires extensive, customized, and often proprietary software engineering ironed out directly between the wireless operator and a single primary core vendor (such as Huawei, Ericsson, or Nokia).
- Network Slicing Disarray: This gap severely crippled Network Slicing. While 3GPP authored elegant logical diagrams for end-to-end network slicing, the absolute lack of unified, cross-domain transport realization standard meant that slicing remained confined to single-vendor testbeds and highly customized, non-scalable deployments for years.
Source: Siarhei Yurchanka/Alamy Stock Photo
The Warning Signs for IMT-2030:
As we look ahead to 6G and IMT 2030 recommendations, the ITU-T remains largely sidelined from mobile core network architecture. 3GPP operates as the de facto absolute authority on both the radio and the cloud core stack. If left uncorrected, the structural loop will repeat. 3GPP will deliver an idealized, highly complex, AI-driven 6G core architecture on paper, leaving actual functional implementations to be sorted out via proprietary vendor middleware.
Light Reading reports, that there are currently three competing 6G core architectures within 3GPP, which threatens to splinter their specs for 6G core networks. Most network operators prioritize affordable evolution, but debates over who controls device intelligence and revolutionary design risk causing divergence. Two fundamental points have emerged: how to handle or embed AI functionality and what to do with non-access stratum (NAS) signaling. NAS is the secure signaling pipeline between the device and core network, handling authentication, encryption, mobility management and session setup. Mobile architectures have relied on it as a foundational pillar since 2G (GSM), embedding it in device baseband silicon and SIM security frameworks.
Reworking NAS requires modem redesign, core security procedure overhaul and device backward-compatibility planning. Inside 3GPP SA2, the study phase has identified three candidate directions for the core network (based on AI functionalities):
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Direction 1 – Separate AI domain: A dedicated AI domain for intent handling independent of the packet-switched network, with the AMF routing NAS signaling while AI fulfillment occurs via SBI; backed by Nokia, T-Mobile USA, Verizon, NVIDIA, Deutsche Telekom, Apple, Qualcomm, Ericsson and NEC, though implementation requires complex UE AI domain client integration.
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Direction 2 – AI functionality in 6G NFs approach: Integrates AI through dedicated 6G network functions following standardized 3GPP procedures with flexible NAS routing (standalone or combined with core functions like AMF); supported by NTT DOCOMO, Samsung, LG Electronics, NEC, IIT Bombay, Vodafone, Apple and China Telecom (partly).
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Direction 3 – AI/agent-handled connectivity approach: Deeply integrates AI/agents into network procedures with dynamic coordination of capabilities and tool invocation, utilizing a signaling routing function (SRF) independent of AMF with user/control plane integration; aligned with Huawei, HiSilicon, China Mobile, ZTE, vivo, CATT, ETRI, Ewha Womans University and OPPO (partly), though it introduces high procedural disruption.
Of these three paths, the first (Direction 1, separate AI domain) has gained the most traction among Western operators and vendors (T-Mobile USA, Verizon, Deutsche Telekom, Nokia, Ericsson, NEC, NVIDIA and, to some extent, Apple). Anchoring the core to the 5G service-based architecture (SBA) interface preserves 5G core investments while letting intent handling mature alongside existing services. However, choosing a direction without standardizing the underlying AI Model Interchange Formats or Agent-to-Agent telemetry will create a brand new flavor of proprietary vendor lock-in.
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Conclusions & Engineering Mandates for the 6G Core:
To prevent an amplification of the 5G SA core interoperability deficit, the global engineering community must pivot away from abstract logical modeling. If 3GPP selects an architectural path for IMT-2030 without standardizing the deep execution and semantic layers, we will simply replace legacy infrastructure silos with an unmanageable layer of proprietary AI middleware.
We must advocate for four critical shifts in our approach to 6G core network standardization:
- Mandate Behavioral, State, and Data Realization: Future core specifications must move beyond simple API syntax definitions and logical block diagrams. 3GPP must explicitly standardize end-to-end state-machine behaviors, cross-vendor error-handling conditions, and database synchronization baselines—specifically defining the realization mechanics for stateless network functions and the Unstructured Data Storage Function (UDSF) layer across multi-vendor boundaries.
- Standardize AI Semantic Frameworks and Agent Telemetry: Choosing a 6G core direction without anchoring it to open, deterministic data layers will trigger an unprecedented form of algorithmic vendor lock-in. Standards must rigidly define AI Model Interchange Formats, intent-handling taxonomies, and Agent-to-Agent telemetry protocols. If an autonomous agent invokes a tool or alters network routing dynamically, its procedural boundary conditions must be universally verifiable across competing vendor stacks.
- Bridge the Transport and Cloud-Native Infrastructure Void: 3GPP must abandon its isolationist posture and actively co-author implementation blueprints with open-source infrastructure bodies (such as the Linux Foundation’s telecom initiatives and the Cloud Native Computing Foundation). Specifications must establish standardized, open baselines for underlying container orchestration, state-data persistence, and low-level user-plane hardware acceleration using eBPF (Extended Berkeley Packet Filter) or DPDK (Data Plane Development Kit) architectures.
- Prioritize Cross-Domain Transport Mapping from Day One: Inter-operator roaming and cross-domain networking cannot be treated as downstream implementation details or left to bilateral vendor agreements. 3GPP must natively bake the mapping mechanics between mobile network slices (S-NSSAI) and IETF-defined transport network layers (such as Segment Routing over IPv6 – SRv6) directly into the initial 6G core architecture.
If 6G is to debut as a truly transformative, global platform rather than an incremental upgrade to radio spectral efficiency, we must bridge the chasm between paper standards and software reality. The architecture of the 6G core must be built from its inception for actual cloud realization, absolute multi-vendor interoperability, and rigorous operational clarity. We cannot afford another ghost in the machine.
If 6G is to be a truly transformative global platform rather than an incremental upgrade to radio efficiency, we must bridge the gap between paper standards and software reality. The architecture of the 6G core must be built for actual realization, true multi-vendor interoperability, and absolute operational clarity. We cannot afford another ghost in the machine like we had with the 5G SA core network specs.
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References:
https://techblog.comsoc.org/2024/12/18/5g-network-slicing-progress-report-with-a-look-ahead-to-2025/
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