First of all, thanks for an excellent product. I've been using SoftEther for several years now and it's been great up until now. I am using it to tie a hosting server on the net to my private server at home to exchange smb traffic, and since it needs to be secure a VPN tunnel using SoftEther is used. Traffic is mostly SMB as the clients connect to it and pulls data from a network share on my server. It's also meant to be used to sync volumes between the main server and backup server. All the data is always flowing from the main connection to the clients, never the other way around, so the only bandwidth that is needed by the clients is download speed.
This is my current setup (simplified):
Home connection (Sweden):
1000/500Mbit. Running SoftEther VPN Server in a Hyper-V VM. No limitations on the server in terms of allowed TCP connections etc. No SecureNAT. Clients connect to it and gets an IP from my DHCP server.
Primary offsite connection (Germany):
1000/1000Mbit. Running SoftEther VPN client in a Hyper-V VM. Dials in to my server, set to 8 TCP connections to max out available bandwidth. Getting around 300-400Mbit-ish speeds depending on server load and routing etc. It pulls data through an SMB share on the main server (Sweden), acting as a relay for the data located in Sweden.
Secondary offsite connection (UK):
300/50 connection. Runs SoftEther VPN client in a Hyper-V VM, with identical configuration as the German connection above. Meant to be used to sync volumes between the main server (Sweden) and backup server (UK) using sync software (RoboCopy, SyncThing, FastCopy etc)
The problem is that regardless what I do it can only open up 2 TCP connections from this client, and the speeds are abysmal across the VPN. I would expect to get similar speeds from the UK site as the others as it's 300Mbit download, but to no avail.
Here are the iPerf speeds just to get an idea what I get from each client:
Germany <> Sweden (using 1 thread, 8 TCP connections):
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[ 4] 0.00-10.00 sec 49.8 MBytes 41.7 Mbits/sec sender
[ 4] 0.00-10.00 sec 49.7 MBytes 41.7 Mbits/sec receiver
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[SUM] 0.00-10.00 sec 376 MBytes 315 Mbits/sec sender
[SUM] 0.00-10.00 sec 375 MBytes 315 Mbits/sec receiver
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UK <> Sweden (using 1 thread, 2 TCP connections (8 TCP connection set)):
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[ 4] 0.00-10.01 sec 6.88 MBytes 5.76 Mbits/sec sender
[ 4] 0.00-10.01 sec 6.84 MBytes 5.73 Mbits/sec receiver
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[SUM] 0.00-10.00 sec 11.0 MBytes 9.23 Mbits/sec sender
[SUM] 0.00-10.00 sec 9.67 MBytes 8.11 Mbits/sec receiver
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As I mentioned, the UK side only opens up two 2 TCP connections even when it's set to 8. Any traffic going through the tunnel is dead slow.
But the kicker is, if we do a SFTP file download from Sweden to UK without the VPN tunnel across only 4 parallel threads we get full speed, so there's nothing wrong with the infrastructure speeds. It's only as soon as we use the VPN things slow down to a crawl. I've tried alternative VPN solutions such as Hamachi and OpenVPN with similar slow results, the only way to get the full speed is by using SFTP or HTTP, but I have not yet found any software than can do proper volume syncing using those protocols. I could skip VPN here if I found something that would work. SFTP is not a solution since it won't be able to preserve file attributes or detect changes etc (as normal sync software would do), and alternative software such as SyncThing, Syncrify, DeltaCopy etc are too slow as they are using only a single TCP connection (whereas with FTP I can use several parallel connections).
The UK ISP reports no traffic shaping or throttling, I've tried different ports, with and without Hyper-V, i've tried with a fresh config of SoftEther client, I've even tried to connect to a secondary SoftEther server in case there were some limitations imposed on the primary, but all with the same slow results. And only two TCP connections even when the client is set to 8, and no restrictions on the server.
So I am at a loss. I need a way to sync the Sweden<>UK site but nothing across the VPN is usable due to the slow speeds, and no other VPN-less solutions are good for syncing or cloning volumes across WAN.
My first attempt at finding a solution was to fix the TCP connections but it only opens up 2 TCP connections, sometimes just one. And I can't figure out why. The other server (German) works just fine every time, and we get good speeds every time, but the UK site refuses.
Does anyone have any ideas what to try next?
Thanks in advance!