Dear OpenVPN developers, I've faced a very strange issue with slow outbound network speed from Windows Server 2016 Standard server via the OpenVPN tunnel. OpenVPN server is Windows Server 2012 R2, client is Windows Server 2016. The inbound network speed for Windows Server 2016 is great. But the outbound network speed is nearly 30-40 kbps. I've got the same results using several tests: iperf testings, file download via SMB, Web-based downloading (using HTTP) etc.
The tunnels is getting up and it works greatly, but only in one direction - from Windows Server 2012 R2 to Windows Server 2016. I've been using such server-client configurations setup for several years with Windows Server 2012 R2 servers and I've never faced such issue before. At first I thought that our ISP has some network limitations, but it turned out that the same tests shows great network speed results using the public IP addresses in both directions. The issue only occurs inside the VPN tunnel. I've spent 3 days tryng to figure it out, but failed. I've installed all latest Windows updates, reinstalled OpenVPN, tried to switch from UDP to TCP, played with performance settings in configs (link-mtu, sndbuf, rcvbuf etc) but still no luck. I've tested the same setup between two Windows Server 2012 R2 servers and it works greatly in both directions. Then I've tested it with another Windows Server 2016 Standard server (different server and different ISP) and it showed the same awful results in outbound direction. When I've set the same OpenVPN tunnel between two Windows Server 2016 Standard servers I've got the same poor network speed in both directions. I believe that the issue is somehow related only to the Windows Server 2016 version and I am more than confident that it depends on server's TCP stack settings. I've noticed that Windows Server 2016 has a congestion control provider setting set to "default", while previous versions of Windows has this setting set to "none". I've created a topic on OpenVPN Support Forum and it was suggested to post my issue to you and reference the thread. You can reference to the https://forums.openvpn.net/viewtopic.php?f=6&t=27173 for config files and additional information. Have you faced a similar issue before? Can you provide any hint how can I resolve the issue? What did I missed? I would be very grateful for any help. Thank you in advance. -- Best regards, *Rostyslav Maryliak* System Administrator *iDeals™ Solutions Group*| + 38(073)437-72-51 <%2B%2038%28093%29575-35-16> | Skype: rostyslav.maryliak.ideals| *rostyslav.maryl...@idealscorp.com <dmitry.zaporozhche...@idealscorp.com>* | www.idealsvdr.com <http://www.idealscorp.com/> -- CONFIDENTIALITY NOTE: The information transmitted, including attachments, is intended only for the person(s) or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and destroy any copies of this information.
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