WireGuard SMB Throughput Slow

RouterOS General
1

I have a working WireGuard setup, as in it connects and routes traffic, but I have a couple of issues to do with throughput and another to do with different behaviours under slightly different traffic conditions.

I connected to WireGuard from my laptop and made some SMB transfers using Windows Explorer. This was slow (<2Mb/s) when it shouldn’t have been (connection speeds at both ends very high) and, when I made two simultaneous file copies, only one copy would proceed at a time - when one was downloading the other wasn’t and they would swap every 10 seconds or so (one of them at 0kb/s while the other downloaded), rather than both downloading and sharing the bandwidth.

First question - why so slow?
Second question - why only one SMB transfer at a time?

The other issue is that my Windows laptop is not able to connect to anything else on my LAN via web browser over wireguard, but my iOS devices are (Edge on Windows and Safari on iOS). This includes the web browser client for the same NAS box as the slow SMB transfers.

Third question - why would SMB to my NAS work (albeit with the above issues) by IP address but not web browser traffic on my Windows laptop, but iOS is able to connect via its browser?

Everything else about my setup works perfectly and has for years.

2

Whats your MTU set to?

Also what is this supposed to mean?

Here legally 15mbits ADSL2 is considered “high”

3

Well, higher than terrible, which is what I am getting. I can replicate the performance at other locations, and the SMB one-or-the-other transfer is/should be independent of the end point network config, shouldn’t it?

MTU of my connection is 1500 (no PPPOE on my home ISP). MTU of Wireguard is 1420.

4

Have you tried to use another speed control like iperf3 or something else, so you see that the smb is slow.

5

I just watch the Windows transfers. If I have 2 simultaneous transfers they are both slow and only one transfers progresses at any time. If I use the same VPN for browsing the web it’s generally a much smoother and faster experience.

How might I fault find this?