Webex Room 55 video loss

[mike1juliet]

Greetings, 

We recently registered a Webex Room 55 running SW ce11.1.4 on a CUCM version 11.5, everything looked good for a few days and now the customer is stating that during VTC's, they will lose video, both ways.  Neither site can see each other, video goes to black screen, audio continues.  The issue can only be resolved by disconnecting and reconnecting call.  We replaced the the ethernet cables to shielded CAT 6e, no sever packet loss or jitter detected.  Only system in our building that is experiencing the issue, and we have other systems connected to the same switch.  System was brand new out of the box, any ideas what is causing this?  Any input would be appreciated.  Thank you.

mike

[Jonathan Schulenberg]

Does video stop at a specific time - for example, correlative to a SIP session refresh re-INVITE?

Does the media statistics show excessive packet loss/jitter prior to video stopping?

[mike1juliet]

Video doesn't stop at a specific time, it's sporadic.  Also, the packet loss/jitter is not excessive before losing video.  There is always some, but not enough to warrant video loss.  

[PJMack]

How much packet loss are you experiencing? On an internal (no internet) call you really should have non, not even a little. How much are you seeing? 

[Ibrahim AlQumairi]

Verify the Quality of Service (QoS) settings. There may not be enough bandwidth available during the Video call, and the policy may be configured to drop connections when the traffic exceeds the limit.

[mike1juliet]

I went to to the QoS settings in the codec and maxed out audio, data, signaling and video, I'll see if this helps, thanks for the idea.

[Jonathan Schulenberg]

What do you mean "maxed out"? DSCP markings by the endpoint must align with the network infrastructure to be effective. There are well established best practices on that front such as RFC4594 and the Cisco Preferred Architecture Bandwidth Management. Change the QoS settings back to their default values unless you understand how to design and implement end-to-end DIffServ model QoS.

[mike1juliet]

Will do, I'll reset setting to default.  Thanks for letting me know Jonathan.  

[mike1juliet]

Thank you to all that responded to my query.  As of right now, the issue still persists.  We don't actually disconnect from the call, we just lose video (black screen).  All settings on the codec are at default the same as other Cisco 55 systems that are not experiencing this issue.  Packet loss is below 1% and Jitter is usually between 5 to 20ms.  The black screen is not correlative to a specific time.  Any other ideas on what it could be?  Thank you .

[Jonathan Schulenberg]

Just to be sure we're chasing the same thing: only the far-end video goes black, correct? The display itself still works and shows locally shared content or the local UI if you end the call, right? Also, does starting/stopping a content share cause video to resume?

You can try a software upgrade on the endpoint but that's a shot in the dark.

After that you'll have to start pulling logs, possibly a packet capture, to see what happens when the display goes black. The first thing I would be looking for is a mid-dialog re-INVITE with different SDP at that timestamp. If there isn't one then you'll have to rely on the log details or RTP stream analysis. You're probably ready for a TAC case if you make it that far though; they can help reading the diagnostic logs.

[mike1juliet]

Yes, only the far-end video goes black.  The display itself still works, if you disconnect from the call, the screen goes back to standby, which is when the customer just dials back in.  I will pull logs next time this happens as you suggested.  

Update: nothing jumped out at me when I pulled the call logs but I will keep looking.  In the meantime, I was wondering if removing it from call manager and registering it to our VCS GK would be a good troubleshooting step?  

[Jonathan Schulenberg]

Sure, if it's readily reproducible, trying it on VCS would be an interesting test. You'd want to be very aware of any differences in the setup and test call compared to CUCM though (e.g. SIP EO vs. DO, SIP vs. H.323, traversal or non-traversal call, etc.) The more differences there are the fewer things you have ruled out.