Slow SSLVPN with Windows 7

[BarryS]

We have a FortiGate 200D on the latest firmware.  Windows 7 computers that connect to the SSL VPN copy data at a fraction of the speed of the Windows 8 PCs.  A 113 mb file that takes under 3 min with Windows 8 takes over 12 min with Windows 7.

I have confirmed the problem with several PCs of several brands, desktop and laptops, wired and wireless.  I have tested over several ISPs and over a cellular connection.  At the request of Fortinet support I have taken a Windows 7 PC that was slow and installed Windows 8 and confirmed the issue was resolved.  These test PCs have nothing loaded but Windows and the FortiClient (VPN only).  No antivirus installed, not joined to a domain.

The servers are Windows Server 2008r2 or 2012r2.  One has Symantec Corporate Security and the other has ESET.  I have tried turning off AV and firewall on the server.

The same computers can be taken to the office and work well.  It is only when going over the FortiClient SSL VPN that we see any problems.  Have tried the latest FortiClient as well as older versions.  Have tried the Win 7 PCs to another FortiGate SSL VPN and not run into the problem.

I have run Wireshark on a problem PC and saw no issues.  I have turned off TCP auto-tuning and looked into Large Send Offload.

The ticket is currently being researched by FortiNet support.  This is a long running problem, any help you can provide will be greatly appreciated.

[Christopher_McMullan]

Is it your case that resulted in a bug report? I came across it this morning.

If so, it looks like the issue is reproducible, so anyone else affected would just need to wait on a fix to be devised and included in future patches. At some point, a Change Order will firm up the fix, and we can look forward to a specific public release that should resolve the issue if you upgrade to it.

[BarryS]

I am not aware of this being a known issue.  We still have no solution.

[Christopher_McMullan]

I'll PM you out-of-band with more information.

In the meantime, if anyone else comes across this thread trying to research their own, similar issue, update the thread with details about your host and tests, and I can work with you to confirm whether this bug affects you.

[ede_pfau]

@Christopher: it would be most helpful if you could name the OS version affected: 5.0.x or 5.2.x branch?