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

Question

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.

Answer 1

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.

Comments

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?

Answer 2

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.