SRX5308 L2TP/IPSec VPN on Windows 10 - Slow Throughput

[HRC_ITguy]

I have an SRX5308 running firmware v4.3.5-3 and a VPN setup based on the configuration provided by @train_wreck in this thread.  WAN1 is on a fiber connection that reliably tests at 500/25 Mbps.  The remote Windows 10 laptop tests at 100/15 Mbps.

The problem I am experiencing is that VPN throughput is speed testing at an abysmal 3/5 Mbps.  File transfers from the box to the client run anywhere from 300 to 700 Kbps.  I attempted adjusting the MTU according to this Netgear KB article, which doesn't matter much because Windows 10 automatically places an MTU limit of 1400 on VPN connections.

After a full day of tweaking, testing, and troubleshooting, I'm at a loss and would appreciate any assistance in getting this issue resolved.

[sovinc]

Did you find a solution for your vpn throughput problem?  I am experiencing the same issue with my VPN.

Thanks.

[HRC_ITguy]

@sovinc No, I have been unable to find a solution.  At some point in time I will have probably have an IT consultant evaluate it and see if that gets us anywhere.  I'll be sure to post back here if I find anything of value.

[sovinc]

Thanks @HRC_ITguy, appreciate the response.

I did come across this article about changing the MTU size:  https://community.netgear.com/t5/Hardware-VPN-Firewalls-and/VPN-Performance/td-p/1279557.  Not sure if you tried this but I'm looking into it for my network.  I'll post back after I test the changes.  

[HRC_ITguy]

@sovinc Thanks for the article link.  I did find similar information throughout the forums and tested various MTU sizes.  There was no improvement in throughput speed for me when doing this.  Hopefully you have better results.