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Why Identity Request Need to be perform by MME after successful Authentication and Security Mode Complete...?

+4 votes
924 views

I saw a scenario where an Identity is requested by MME after successful Authentication and Security mode complete.. As a Response to this message UE is Sending IMEI? what is the need of checking IMEI number after successful authentication? If IMEI is in block list then ongoing Attach procedure is going to be Terminate...? Identity Request intention is mainly to check the IMEI belongs to any one of Black, while or Green list then why cannt MME check for this before Security Mode?

posted Mar 17, 2015 by Srinivas Sambari

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Is it defined somewhere in specifications or not ?
I saw this behavior while analyzing a log file

1 Answer

+1 vote

In Attach request, UE sends GUTI information. MME/HSS stores GUTI to IMSI mapping.

When UE is attaching, if MME does not have mapping to GUTI received from UE, it will request for identity from UE .ie. it will send out Identity request message and UE will respond with IMSI if identity type requested is 1

If identity type requested is 2 then UE will respond with IMEI. I am not sure in what case IMEI is requested.

In case MME has mapping, you will not see identity request going out from MME

Why this is done after security mode procedure is because if IMSI is sent in attach request it is prone to interception because message is not encrypted and this is the reason GUTI is sent by UE

Spec:
Reference: 3GPP TS 24.301

answer Mar 21, 2015 by Alkesh Mehta
With IMEI you can identify Ue type and therefore perform analysys of thr traffic, failures in terms of UE type.
Similar Questions
+3 votes

There are couple of procedures are defined which consist of NAS as well as RRC signalling messages exchange.
Some of the NAS message sends to an UE through RRC Connection Reconfiguration message as piggybacked and some as DL Info transfer.

I want to know, Is there any procedure exists in lte when an UE receives RRC Connection Reconfiguration along with NAS message and responds back to network with NAS message first and then Reconfiguration Complete to eNodeB.

Usually, I saw UE sends RRC Connection Reconfiguration Complete message first then NAS response message.

+2 votes

What is the objective to send the ESM Information Request message to UE ? Does it part of attach procedure ?

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