When does MME execute Identification procedure ?

Question

In what all scenarios, this procedure gets executed ? And why this procedure need to be executed ?

Answer 1

If ue sends old guti in attach request and If the UE is unknown in both the old MME/SGSN and new MME using the old guti, then the new MME sends an Identity Request to the UE to request the IMSI. The UE responds with Identity Response (IMSI).

Comments

I would like to add my comment here.
Identification procedure is performed by MME in two interfaces, those interfaces are S10 and S1-AP .

There are two different scenarios in which identification procedure is used to resolve the UE details.
First scenario-->
MME receives attach request from the UE with GUTI . Based on the GUTI details , new MME resolves old MME and forward the received attach request and GUTI information to old MME by using "Identification Request" message. If old MME responds with failure then new MME executes "Identity Procedure" towards the UE to get the UE's details like IMSI.


Second scenario:
This scenario is unlikely to happen when new MME is not able to resolve old MME address based on the received GUTI. In this case, nothing will exchange between MMEs but new MME executes S1-AP based Identification procedure to get the UE Identity.