Dear 4G Experts.
I am facing issue of getting E-RAB Modification request from MME after assigning QCI 5 ARP = X and QCI 5 ARP changes to New value Y.
Please advise.
Why is this troubling you?
This is normal scenario.
We are testing at Lab and getting this issue.
ARP change is normal?
ARP change must be triggered by Core.
I am saying eRAB modification is normal.
Check with your Core team.
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What is the value before and what is after?
Does this happen every time for every UE?
Does this happen in one sequence without any trigger i.e. UE attaches and get eRAB establishment and then eRAB Modify?
8 & 6
Yes.
YES, in same flow like when UE get S1AP_ERAB_SETUP_REQ message and then S1AP_ERAB_MODIFY_REQ message from MME.
Can you also check and confirm if this Modify happens before or after UE triggers SIP connection with IMS?
Theory: Core network (HSS, PGW etc.) have certain information regarding what bearers need to be setup for new UE.
But usually this shouldn’t change.
Modifying happens if and when application servers (IMS, PTT) trigger some action (toward PGW) and that requires a different bearer type i.e. (a different ARP etc.) so PGW sends Modify message.
Raise this issue with Core team please.
Tell them this is a really important issue since this can cause Signalling Storm.
Imagine site goes down and then suddenly all users come back online at same time.
These modify messages are unnecessary extra load on network.
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