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Weird MRA unanswered calls (over Expressway) when 4G mobile is used


We have implemented an Expressway MRA system with CUCM 11.5.

Clients are Android mobile client with newest Jabber. All of clients connecting via MRA (ExpE-ExpC).

When client connected to wireless network (still MRA, over ExpE-ExpC), all of calls will be successful.

But when connected to stable 4G network, sometimes the client cannot ring, just display  an "Unanswered Call" notification.


Tried to debug at CUCM/Expressway pair - and I can see that CUCM sends an 


- Gets back a Trying from ExpC

- after that sends a CANCEL 


Just a note, not all of the time this issue is occured. Sometimes yes, sometimes not.


What could be caused this issue? Why CUCM send Cancel before receive Ringing and 200OK?

Is it a timer? The SIP profile in CUCM is "Standard SIP Profile for Mobile Device" with default values:




I assume the internet connection is stable  - as CANCEL arrived in time to client.



When comparing a working and non-working example, what’s different in the SIP trace between CUCM and Expressway-C? My guess is that a 183 Session Progress follows the 100 Trying in the working example. If that’a what it is you need to pull logs from the Expressways and Jabber client: did the client ever send one and if yes, did Expressway-E get it? That’s where I would start at least. Keep an eye on the header/SDP differences between working and non-working.

No, there was not 183 Session in progress, just 180 Ringing - at the successful call.

When call was unsuccesfull, there was not any 180 ringing back, and  CUCM send CANCEL .

If it is a timer, it just occured at mobile calls, as wirelessly connected Jabber clients working definitely well.


Please take a look to the following diagrams (from CUCM trace)


The successfull call was the following:

The Cancel at 11:59:28 is when the caller on-hooked the phone. So this CANCEL was occured by tester staff.



But at the unsuccessfull call, there was not any ringing back, and maybe the Callmanager send a Cancel at 11:59:20 , eight (8) seconds earlier as caller on-hooked call. So this CANCEL was not occured be test-staff, it is occured by Callmanager.




VIP Advisor

on the android client, use the "send problem report" option and analyze this, if needed add to this post

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To tell the true - I cannot found any interesting at log. Attached it.

The time when we see a missed call notifocation (as the only one) at client side is:


2018-05-25 11:59:23,164 INFO  [0x00000001b4fb2b40] [miscs/YLCLocalNotificationManager.m(379)] [UI.Action.System] [-[YLCLocalNotificationManager sessionDidEnd:]] - jabber post a notification[You have missed a call] at 2018-05-25 09:59:23 +0000

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