School of Specs 24.501v20.0.0

3GPP 24.501 v20.0.0 — the document's own text

4.1 Overview

Taught in 1. What CT1 is, and the three names it answers to (CT1 — the group that writes what your phone says, in depth), 2. Stage 3 — the difference between a plan and a protocol (CT1 — the group that writes what your phone says, in depth), 4. TS 24.501 — two protocols living in one document (CT1 — the group that writes what your phone says, in depth), 5. Finding your way around TS 24.501 (CT1 — the group that writes what your phone says, in depth), 10. Who CT1 writes to, and what the letters count (CT1 — the group that writes what your phone says, in depth), 12. The neighbours — and how little the record says about them (CT1 — the group that writes what your phone says, in depth), 1. The group that writes what your phone says (CT1 — the group that writes what your phone says, overview), 2. Architecture and protocol — what stage 2 and stage 3 mean (CT1 — the group that writes what your phone says, overview), 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview), 2. What the group produces, and what one of its documents looks like (CT1 — the group that writes what your phone says, quick start).

The non-access stratum (NAS) described in the present document forms the highest stratum of the control plane between the UE and the AMF (reference point "N1" see 3GPP TS 23.501 [8]) for both 3GPP and non-3GPP access.

Main functions of the protocols that are part of the NAS are:

  • support of mobility of the user equipment (UE) including also common procedures such as authentication, identification, generic UE configuration update and security mode control procedures;
  • support of session management procedures to establish and maintain data connectivity between the UE and the data network; and
  • NAS transport procedure to provide a transport of SMS, LPP, SLPP, LCS, UPP-CMI container, UE policy container, SOR transparent container and UE parameters update information payload.

Principles for the handing of 5GS security contexts and for the activation of ciphering and integrity protection, when a NAS signalling connection is established, are provided in clause 4.4.

For the support of the above functions, the following procedures are supplied within this specification:

  • elementary procedures for 5GS mobility management in clause 5; and
  • elementary procedures for 5GS session management in clause 6.

Signalling procedures for the control of NAS security are described as part of the 5GMM common procedures in clause 5.4.

Complete NAS transactions consist of specific sequences of elementary procedures. Examples of such specific sequences can be found in 3GPP TS 23.502 [9].

The NAS for 5GS follows the protocol architecture model for layer 3 as described in 3GPP TS 24.007 [11].