SOLUTION: Users drop from IM conferencing

Applies to Lync 2010 Server Enterprise, Communicator 2007 and Lync 2013 client.


Communicator 2007 client creates a large IM conference more than 100 users. But after sometime, users (including the creator user who invites others to the IM conference) start to exit from conference. Eventually few users left in the conference or even some time conference creator is the only user left in the conference! And this issue occurs several times in a day.

I observed the same issue on users with Lync 2013 Client Software.

I also confirmed that it is not an issue of 4 hours conference idle timeout limit. Users actively send IMs.


Increase TCP Idle Time Out value on hardware Load Balancer that load balances  Lync 2010 Front End servers to 30 Minutes (1800 seconds). (which was 20 minutes before)

I observed that this created significant change. Now we got only 1-2 problems in a mount.(which can be caused by another reason, PC, user, network problems etc. I did not want to get client logs and troubleshoot the problem that occurs very rare!)

More Info:

Hardware load balancer requirements for Lync Server 2013

Here there are very “nice” statements:

Although it is written that:

“Typical hardware load balancer configurations use source-address affinity and a 20 min. TCP session lifetime, which is fine for Lync Server and Lync 2013 clients because session state is maintained through client usage and/or and application interaction.”

but again in the same document says 1800 seconds as a requirement:

“Following are the hardware load balancer requirements for Director and Front End pool Web Services:

Use TCP idle timeout of 1800 seconds.”

So I followed the requirement.

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