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External Lync 2013 clients cannot upload ppt or other files and whiteboard, poll, Q&A are greyed out on Lync client

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Hi again,

 

In this blog post, I want to talk about a Lync 2013 problem where external users fail to upload powerpoint presentations. When external Lync user tries to upload a ppt file to an online meeting, basically nothing happens and once the failure occurs, all web conferencing related features are greyed out on the client afterwards as displayed below:

 

Interestingly the same issue happened with any file uploads not just ppt files and it was possible to reproduce the behavior even with Lync 2010 client. These findings eliminated an Office Webapps issue. Interestingly the client was able to establish a session with Webconf edge service as per the network trace collected on the client:

 

Note: The real web conferencing server IP address was deliberately replaced with 192.168.220.7 for privacy purposes.

 

No. Time Delta Source Destination Protocol Length Info

   3892 2013-09-26 11:20:53.672 0.000 192.168.1.30 192.168.220.7 TCP 66 65021 > 443 [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=4 SACK_PERM=1

   3893 2013-09-26 11:20:53.796 0.123 192.168.220.7 192.168.1.30 TCP 66 443 > 65021 [SYN, ACK] Seq=0 Ack=1 Win=4356 Len=0 MSS=1452 WS=1 SACK_PERM=1

   3894 2013-09-26 11:20:53.796 0.000 192.168.1.30 192.168.220.7 TCP 54 65021 > 443 [ACK] Seq=1 Ack=1 Win=132132 Len=0

   3895 2013-09-26 11:20:53.797 0.001 192.168.1.30 192.168.220.7 TLSv1 183 Client Hello

   3903 2013-09-26 11:20:53.927 0.130 192.168.220.7 192.168.1.30 TLSv1 1506 Server Hello, Certificate[Unreassembled Packet]

   3904 2013-09-26 11:20:53.934 0.006 192.168.220.7 192.168.1.30 TLSv1 1506 Ignored Unknown Record

   3905 2013-09-26 11:20:53.934 0.000 192.168.1.30 192.168.220.7 TCP 54 65021 > 443 [ACK] Seq=130 Ack=2905 Win=132132 Len=0

   3906 2013-09-26 11:20:53.941 0.006 192.168.220.7 192.168.1.30 TLSv1 1506 Ignored Unknown Record

   3907 2013-09-26 11:20:53.941 0.000 192.168.220.7 192.168.1.30 TLSv1 200 Ignored Unknown Record

   3908 2013-09-26 11:20:53.941 0.000 192.168.1.30 192.168.220.7 TCP 54 65021 > 443 [ACK] Seq=130 Ack=4503 Win=132132 Len=0

   3909 2013-09-26 11:20:53.950 0.008 192.168.1.30 192.168.220.7 TLSv1 368 Client Key Exchange, Change Cipher Spec, Encrypted Handshake Message

   3918 2013-09-26 11:20:54.075 0.125 192.168.220.7 192.168.1.30 TCP 60 443 > 65021 [ACK] Seq=4503 Ack=444 Win=4799 Len=0

   3919 2013-09-26 11:20:54.079 0.003 192.168.220.7 192.168.1.30 TLSv1 101 Change Cipher Spec, Encrypted Handshake Message

   3920 2013-09-26 11:20:54.080 0.001 192.168.1.30 192.168.220.7 TLSv1 898 Application Data

   3928 2013-09-26 11:20:54.215 0.134 192.168.220.7 192.168.1.30 TCP 60 443 > 65021 [ACK] Seq=4550 Ack=1288 Win=5643 Len=0

   3929 2013-09-26 11:20:54.215 0.000 192.168.1.30 192.168.220.7 TLSv1 83 Application Data

   3931 2013-09-26 11:20:54.335 0.119 192.168.220.7 192.168.1.30 TCP 60 443 > 65021 [ACK] Seq=4550 Ack=1317 Win=5672 Len=0

   3973 2013-09-26 11:20:55.080 0.745 192.168.1.30 192.168.220.7 TLSv1 1094 Application Data

   3982 2013-09-26 11:20:55.218 0.137 192.168.220.7 192.168.1.30 TCP 60 443 > 65021 [ACK] Seq=4550 Ack=2357 Win=6712 Len=0

   5353 2013-09-26 11:21:23.238 28.019 192.168.1.30 192.168.220.7 TLSv1 86 Application Data

   5360 2013-09-26 11:21:23.420 0.182 192.168.220.7 192.168.1.30 TCP 60 443 > 65021 [ACK] Seq=4550 Ack=2389 Win=6744 Len=0

 

On the other hand, there was a weird behavior that was observed in the above trace. If you pay closer attention, you’ll see that there’s no response from Web conferencing edge service at application layer even though the client gets TCP ACKs at transport layer.

 

Then I checked the topology file and realized that there were two Edge servers in the Edge pool and the webconf edge IP address that the Lync client was communicating with didn’t belong to any of the edge servers which means there was a HW load balancer publishing the Edge server pool. Our customer also confirmed that there was an F5 load balancer running in front of the Edge pool.

 

I asked our customer to bypass the HW load balancer by putting one of the Edge Server’s dedicated IP addresses for access edge/webconf edge/av edge services in the HOSTS file on the external Lync 2013 client. Once that was done the issue did’t occur anymore which means either load balancer itself has a configuration or similar problem or there’s a connectivity problem with the F5 load balancer and the Edge server external interfaces.

 

Hope this helps

 

Thanks,

Murat

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