Section: 5.40.6 Prevention of signalling overload related to Disaster Condition and Disaster Roaming service
Content: The load control, congestion and overload control mechanism specified in clause 5.19 and access control and barring specified in clause 5.2.5 can be used to mitigate the load caused by UE requesting the Disaster Roaming service in the PLMN providing Disaster Roaming service and returning of UE to allowable PLMN when Disaster Condition is no longer applicable. To prevent signalling overload in PLMN providing Disaster Roaming, the HPLMN or registered PLMN: - may provide the UE in a prioritized manner with the list of PLMNs described in clause 5.40.2 for Disaster Roaming; - may provide disaster roaming wait range information to control when the UE can initiate the registration for Disaster Roaming service upon arriving in the PLMN providing Disaster Roaming service as specified in TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [17] and TS 24.501[ Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3 ]  [47]; and - applies Access Identity 3 for Disaster Roaming service request as specified in TS 24.501[ Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3 ]  [47]. NOTE: The mechanisms available at the AMF and the SMF for mitigation of overload and congestion are used for 5GSM congestion mitigation during the Disaster Roaming. To prevent signalling overload by returning UEs in PLMN previously with Disaster Condition which is no long applicable, the HPLMN or registered PLMN: - may provide disaster return wait range information to control when the UE can initiate the registration upon returning to the PLMN previously with Disaster Condition as specified in TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [17] and TS 24.501[ Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3 ]  [47].