Feature Description

AMF supports the authentication activities and the GUTI (Globally Unique Temporary Identity) reallocation configuration control for call flows.

GUTI

GUTI is used to keep the subscriber's IMSI confidential. AMF allocates a GUTI to the UE. It's composed of PLMN ID, AMF ID, and TMSI. As it's a temporary identifier, its associations aren’t fixed to any specific subscriber or mobile. A single 5G-GUTI is used to access the Security Context of 3GPP and non-3GPP technologies within the AMF.

Supported Functions

AMF supports the following functions:

  • Authentication and GUTI reallocation counter maintained as per the UE. For each supported type, separate counters are maintained.

  • Time reference per UE for network-initiated GUTI reallocation

  • GUTI reallocation attempted as per the configuration for a specific time interval.

  • Includes the new GUTI in either Registration Accept or Configuration Update Command NAS message

  • AMF shows the allocated GUTI and the allocated time in the show subscriber command output.

Note

Collision of GUTI reallocation in Registration Accept or Configuration Update Command with other procedures isn’t supported.

Supported Scenarios

This feature supports the following scenarios based on the UE on time and frequency of access attempts. These scenarios are part of the Registration and Service Request procedure:

  • Selective authentication

  • GUTI reallocation

The frequency supports access attempts per UE and not across UEs.

Unsupported Scenarios

The following scenario isn’t supported:

  • Authentication requirements dependent or based on EAP-AKA or EAPAKA' or EAPAKA Prime

  • When the latest GUTI isn’t acknowledged, the UE is paged simultaneously with the old and the new GUTI.

Note

GUTI reallocation process takes place only for the successful procedure.

For more information, see the AMF Authentication and GUTI Reallocation Configuration Control chapter.