Node-level Call Flow

This section describes the Node-level call flow.

Node-level Call Flow
Node-level Call Flow Description

Step

Description

1

If the UE wants to register for the emergency services, it sets the registration type to Emergency. When the UE inherits a Globally Unique Temporary ID (GUTI) from the previous 5G registration, it uses GUTI in the Registration Request.

2

If the UE provides a foreign GUTI, the AMF sends the Identity Check Procedure to retrieve the SUCI of the UE. If the AMF fails and authentication is optional, it retrieves Permanent Equipment Identifier (PEI) of the UE.

3

The AMF sends the Security Mode Command message to the UE.

4

The UE responds to the AMF with the Security Mode Complete message.

5

In the Initial Context Setup Request, if the Emergency Services Profile does not require authentication, the AMF signals support only EIA0 and EEA0 based on the integrity protection and encryption algorithms. This algorithm forces the gNB to process the INITIAL_CONTEXT_SETUP procedure without a specific security algorithm from the UE on the RRC interface.

6

The gNB responds with INITIAL_CONTEXT_SETUP response to the AMF.

7

The UE responds with the Registration Complete message to the gNB.