CUCM and Expressway interworking on B2B, CUCM tears up the call (BYE - resource unavailable)

[Liv_Liv]

Hi all,

I´ve got the following scenario: 
SIP video endpoint -> CUCM -> SIP trunk -> Expressway-C -> Expressway-E -> Webex cloud (internet)

The sip video endpoints are registered in CUCM which is v10.5. Both expressways are X.8.8.2.

We are trying to make outbound  calls to Cisco Webex cloud services from another company (let´s say NewCorp), but once in the room, our CUCM is dropping the call at the same time in all cases. 

We can see in the traces & logs the following behaviour: 

- Once the call is established to destination 1234567@newcorp.webex.com, at some point in the middle of the call, Expwy-E generates another INVITE with SDP that forwards to Expwy-C. Expwy-C forwards this INVITE to CUCM. This invite has the following in its attributes: a=sendrecv
- CUCM at first replies to this INVITE with a 200 OK with SDP but with this attribute: a=inactive
- CUCM then sends a BYE to Expwy-C with the reason: Q.850 ;cause=47 (Resource unavailable, unspecified) and the call is disconnected. 

We tried to set up a MRGL with xcode and MTP on the CUCM trunk to Expwy-C with no luck. 

However when I started troublethooting this issue and checked the setup, I found trunk in CUCM had "MTP required" checked, but I know that B2B calls to the Webex cloud never worked before.

Also, I saw that the CUCM trunk has the option "Early offer support for voice and video calls" set as "Mandatory (insert MTP if needed)" in its corresponding sip profile.

Is there anything else I can test in order to solve this issue? dropped calls only happen in our environment is this scenario (calls to Webex cloud).

Also I would like to know why the Expwy-E does generate an extra INVITE in the middle of the call, is this something related to a need of session refresh? is there any way to suppress it?

thanks in advance for your help.

[Roger Kallberg]

I usually set it to not require an MTP on the trunk and have this setting in the SIP profile.

This has worked on any setup that I've been involved with.

[Liv_Liv]

many thanks for your help & reply, Roger.

I tried what you are suggesting with no luck, I get the same result if I change EO setting to best effort. 

thank you,

[Roger Kallberg]

Just to be sure, did you reset the SIP trunk in CM after you did the change for it to take effect?

Your version of Expressway is quite ancient, is there any specific reason to why you don't upgrade it to the latest in the release train that your on? That would be X8.11.4.

[Liv_Liv]

Hi Roger, thanks again.

yes I ensured that the trunk was reset after the modification in the SIP profile. In fact I tried that twice. 

By now an upgrade to 8.11 is not planned because of business reasons, there isn´t much more I can say on that as I don´t take the decisions in my company. However in my company we have another customer with the exact same 8.11 version you are mentioning and they are having the same issue with Webex calls.

thanks,

[Liv_Liv]

Any other ideas or suggestions anyone?

thanks in advance,