Modular NAS Protocol Design for 6G

6G aims to provide significant advantages compared to 5G while being designed to be energy-efficient and quantum-safe from the start. Goals for 6G include superior radio performance, ubiquitous connectivity using Satellite (Non-Terrestrial Networks, NTN) and Wi-Fi, native artificial intelligence (AI) support, a modular design enabling delivery of new features in a modular manner and scalable networks for diverse device types. In this paper, we present a modular Non-Access Stratum (NAS) approach allowing new NAS features to be upgraded and deployable without impacting other NAS features that are already deployed. We include a high-level view of the 6G System architecture, and a detailed view of modular NAS protocol stack, including NAS message routing, User equipment (UE) identifiers and NAS security architecture. We conclude with an outlook for future work.