NAS Congestion Control Call Flow

This section describes the NAS Congestion Control call flow.

NAS Congestion Control Call Flow
NAS Congestion Control Call Flow Description

Step

Description

1

UE sends the Registration Request, Service Request, and Uplink NAS Transaction Request to AMF.

When the NAS congestion configuration is enabled, the AMF accepts the following:

  • Requests received for emergency services.

  • De-Registration Request that originated in the UE.

  • Mobility Registration Update requests received when UE is in the CM-CONNECTED state.

  • Service request received when UE is in the CM-CONNECTED state.

  • Service request that is received in response to a paging request.

  • UL NAS Transport (Payload container type: N1 SM information) PDU Release.

2

Depending on AMF's overload capacity, it may reject the following requests:

  • Service request received when UE is in CM-IDLE state.

  • Periodic Registration Requests.

  • Mobility Registration Update requests received when UE is in the CM-IDLE state.

  • Nonemergency Initial Registration Requests.

  • Uplink NAS Transport requests with payload container type as N1 SM information.

  • Uplink NAS Transport requests with payload container type as SMS) dropped on AMF.