Hi Huawei VoLTE Experts:
In my case, call suddenly getting dropped after SRVCC with:
- SRVCC PS to CS successful
- Bearer deleted
- UE context released
Then call Getting disconnected in random calls at DTAP CC protocol with cause “Destination out of order”
Can someone please comment what can be a possible reason of disconnect and what is this cause?
Check the other side of the call. It may be dropped already.
I’d think this is more switching problem in Core than problem with MO or MT sides.
Core has to switch to calls to MSCs and it might be possible that one of the routes aren’t correctly defined so in those cases the call doesn’t connect properly.
Also likely that higher layers treat this error as destination unavailable or out of order.
You can ask core guys failure rate per MSC. If failures are due to specific region or pool of MSCs then there will be your answer.
Cause No. 27 “destination out of order” (UMTS specific cause values for call control) This cause indicates that the destination indicated by the mobile station cannot be reached because the interface to the destination is not functioning correctly. The term “not functioning correctly” indicates that a signalling message was unable to be delivered to the remote user; e.g., a physical layer or data link layer failure at the remote user, user equipment off-line, etc.
UE context release completed. And drop not reporting in counter KPI.
I have raised it with Core.
You can also do this: Check the failure cause and map it on the sites and RNCs.
Usually pooled RNCs are pooled with MSCs.
Do a trace in the CORE side E2E, to check message release or delete the bearer.
I had the same problem.
At that time it was Core issue.