Section: 6.14 Steering of roaming security mechanism 6.14.1 General
Content: This clause describes the security functions necessary to support steering of the UE in the VPLMN during registration procedure and also after registration as described in TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [53] Annex C. The security functions are described in the context of the functions supporting the control plane solution for steering of roaming in 5GS. If the control plane solution for Steering of Roaming is supported by the HPLMN, the AUSF shall store the latest KAUSF after the completion of the latest primary authentication. The content of the Steering List as well as the conditions for sending it to the UE are described in TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [53] Annex C. The Steering List includes either a list of preferred PLMN/access technology combinations, a secured packet or the HPLMN indication that 'no change of the "Operator Controlled PLMN Selector with Access Technology" list stored in the UE is needed and thus no list of preferred PLMN/access technology combinations is provided'. NOTE1: If a SOR-AF is involved in providing the content of the Steering List as described in TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [53] Annex C, the SOR-AF belongs to the HPLMN. NOTE 2: The Steering of Roaming Information is defined in clause 1.2 of TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [53]. It contains thus the ACK indication, the Steering List and the integrity protection information.