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Freezing screen sharing sessions in MS Teams

asked 2021-06-12 15:48:45 +0000

JasMan gravatar image

updated 2021-06-12 15:52:46 +0000


Has anyone experiences in troubleshooting Teams sessions?

We're facing an issue during screen sharing in MS Teams in one of our locations.

When more than two attendees from different locations joining a Teams session (no peer-to-peer session, traffic runs through M365 network), and one of them shares the screen, some of the attendees in only one location complaining that the screen sharing stream freeze for up to 10 minutes on their clients. All other attendees in other locations are fine. If the affected clients work from a different location they're also fine. Audio and video is always fine, even if the screen sharing stream freeze.

My conclusion so far:

  • Not an client issue, otherwise they should be affected by this issue in other locations as well.
  • Not an issue of the screen sharing source, otherwise all attendees should have the issue at the same time.
  • Video and audio are fine, so no bandwidth issue.

I've captured the traffic of one client during a meeting when the screen sharing stream freezed up. I can see that the screen sharing stream bandwidth drops down when the issue occures. But there's still traffic.

I/O Graph

I will prepare the capture for sharing tomorrow. Any suggestions?

Thanks Jas Man

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2 Answers

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answered 2021-06-18 20:49:31 +0000

JasMan gravatar image

Solved. Wasn't a network issue. I've cleaned up the cache folder of Teams (%appdata%\Microsoft\Teams) and the cache of IE and Edge.

But I'm wondering why the users told me, that they had this issue only at this location. That's why I looked to the network related things first.

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@JasMan: Thanks for letting us know. It is very interesting to know, that such kind of error can cause such issues.Great catch!

Christian_R gravatar imageChristian_R ( 2021-06-19 10:22:59 +0000 )edit

answered 2021-06-12 18:25:42 +0000

Christian_R gravatar image

updated 2021-06-13 16:31:15 +0000

HI, cool IO Graph. Thx for the idea.

Once I have seen such of hanging screens. There the solution was to disable the antivirus checks for Teams in the firewall. Can also fit here, since I understood that only a special location is affected

I personal had issues with teams, while sharing video and screen when my computer ran at around 90% memory usage.

BR Christian

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Hey Packet-Hero :) Thank you for your thoughts. I will check the ressources of the affected clients.

To be honest I'm also pretty sure that some kind of firewall/IPS/antivirus at this location is responsible for this issue. What else could harm only this special stream than a firewall/IPS system.

I've no chance to verify if packets get dropped for this UDP stream, or have I? The application layer is encrypted, and I can't find any other values which are continuously growing per packet.

JasMan gravatar imageJasMan ( 2021-06-13 12:34:59 +0000 )edit

Well I don't think that the packets are dropped. At the case I know about, it was a hold back of packets for antivirus checking. Do you know the manufacturer of the firewall at that specific site?

Multi segment analysis of en encrypted UDP flow is of course complicated, if you are not able to decrypt them. You need to capture in front and behind the firewall and then you can try to compare them somehow. Do you have such two traces?

Christian_R gravatar imageChristian_R ( 2021-06-13 16:28:38 +0000 )edit

The firewall manufacture is CheckPoint.

It's a bit difficult to capture on both sides, because everything is HA. Means we've two lines, gateways, firewalls, switches, etc., and I don't know which way the stream takes.

JasMan gravatar imageJasMan ( 2021-06-15 09:17:42 +0000 )edit

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Asked: 2021-06-12 15:48:45 +0000

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Last updated: Jun 18 '21