Hello Experts,
I’m not too familiar with the MME and Access Network side (PGW doesn’t care where you are!), but what happens for an active data session if you are handing over between the MME pool in that same situation and it fails?
On that TAC border would you have MME and SGW having connectivity to both eNB or its more of a hard-handover?
In that case I’d guess it’s same result you’d lose the bearers right?
Probably better to force SRVCC mid-call before the handover if you can?
Most of the networks are using the SRVCC depending on the coverage quality.
That’s usually based on handset measurement though I think.
Not packet loss or congestion unless there is a vendor feature?
Yes, You’re right.
Would be nice if PCRF could be in control!
PCRF will handle the situation during congestion.
It will stop data sessions and give priority to voice calls.
Can it trigger SRVCC though?
By sending policy for bearer?
PCRF not triggering anything.
Just checking policy charging.
User profiles with HSS.
And arrange bearers priorities.
Yeah that’s true, but I thought it had potential to be like CAMEL and have some logic and control.
R&D part 
.
I found this page for S1 based handover it doesn’t show S1U but does have S1MME going to different MME I just wonder if this means there is no going back it’s like a handover or delete bearer situation?
https://www.sciencedirect.com/topics/engineering/handover-procedure
In the case of the original question about VoLTE handover I don’t see any difference to handling a connected data session on S1 based handover to another MME with different TAC at same time.
I think if HO cannot progress for some reason then new MME will have no context of UE and its likely to be bearer drop scenario from RAN perspective.