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

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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