Handling 5G to 4G TAU when n1-mode is not Supported

Feature Summary and Revision History

Summary Data

Applicable Product(s) or Functional Area

MME

Applicable Platform(s)

  • ASR 5500

  • VPC-DI

  • VPC-SI

Feature Default

  • Disabled - Configuration Required

Related Changes in This Release

Not Applicable

Related Documentation

  • MME Administration Guide

Revision History

Revision Details

Release

MME supports Tracking Area Update (TAU) with N1 Mode = Not supported.

21.28.m5

Support is introduced for a dynamic selection mechanism to select PGW-C+SMF and peer-AMF.

21.25

The N26 interface for interworking with 5GS functionality is fully qualified in this release.

21.20.3

MME supports N26 interface between AMF in 5GC and MME in Evoloved Packet Core (EPC) to provide seamless session continuity for single registration mode UE.

Important

 
This feature is not fully qualified in this release, and is available only for testing purposes. For more information, contact your Cisco Account Representative.

21.20

First introduced.

This release supports N26 Interface for interworking with 5GS functionality.

Important

 
This feature is not fully qualified in this release, and is available only for testing purposes. For more information, contact your Cisco Account Representative.

21.19

Feature Description

During a 5G Standalone (SA) operation to 4G network, if the MME uses N1 Mode flag to decide N26 (AMF->MME) or S10 (MME->MME), it might lead to a Tracking Area Update (TAU) failure and the device can lose its data session.

To overcome such scenarios, MME supports TAU with N1 Mode = Not supported. MME considers AMF as peer if N1-Mode-Reg bit is set to 5GMM-REGISTERED in the UE Status IE.

For more information, see the Use case section in the 5GS Interworking using N26 Interface Support chapter in the MME Administration Guide.