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MME behavior when s1 Setup req is received twice from same eNB

0 votes

Hi All,

I have a query regarding S1 setup procedure.
If MME receives S1 setup Request message from same eNB twice (Assuming the S1 connection is already up), what will be the behavior of MME in this case.
Will it erase both UE and non-UE related application data? Or does it send S1 setup failure message?

Thanks in advance.

posted May 16, 2017 by Sumit Deshmukh

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2 Answers

0 votes

As per my understanding of LTE system so far, LTE eNodeB acts as client and MME acts as server. This is very rare case even I have not simulated but MME will consider new S1-setup Request message and will clear all existing context of same eNodeB.

answer May 16, 2017 by Rupam
Thanks for your response Rupam. As you mentioned that MME would clear all existing contexts of the eNB, but will it erase S1AP UE contexts (if any) also for the same?
0 votes

It is vendor dependent. Sometimes a UE may release the connection and immediately request another S1 setup. If MME has not yet released the 1st connection, it will not respond to the second one and UE might face S1 setup failure. Normally vendors are incorporating such exception handling procedures in new version releases and patches.

answer May 17, 2017 by Faisal Adeem Siddiqui
Similar Questions
+1 vote

Generally MME serves a group of tracking areas and belongs to at least one PLMN.
Lets assume, MME receives S1-setup request from eNodeB with the list of supported TAs.
Now, there are three possibilities as captured below.
1. All supported TAIs match at MME
2. Not even a single TAI match at MME
3. Few TAIs match at MME

I want to know, what MME will do for case 2 and case 3 ? How it will respond to eNodeB ?
If MME responds with S1-setup failure then what would be the cause value ? I did not find any reference in 36.413 for these scenarios.

+2 votes

I have a use case in which
ENodeB sends "S1-Setup Request" message to MME. TAC within the request is unknown for MME but at least one PLMN from the list of broadcasted PLMN is known by MME. How MME shall react ?

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