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I am having issues with OpenVPN while transferring a file through the SMB protocol. The issue is that the speed begins high for the file transfer, goes down and then it keeps going up and down at regular intervals. Probem Both the server and the client are windows.

What I have tried to fix:

1- I changed the MTU settings on both the server and client to mssfix 1420. I tried to change also the other related configs such as fragmentation but there was not really any improvement. This works with the ping test.

2- I changed the buffer size using, on the server side: sndbuf 524288 rcvbuf 524288 push "sndbuf 524288" push "rcvbuf 524288"

3- I have removed the lzo compression.

4- The server is listening on port 443 to avoid interference by the ISP.

5- The cypher is: cipher AES-128-CBC # AES

6- The used protocol for OpenVPN is UDP.

With the default configuration from OpenVPN, the situation was much worse. There was not the peak at the beginning. I managed to improve a bit by changing the MTU and the port.

Is there anything I can do to make this transfer constant?

I know I can because if I open a RDC to the server and copy a file through it the speed remains constant.

Thank you so much!

Scudelari
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  • Have you tried to send a file to the server and measure the bandwidth without VPN? And switching to 443 doesn't necessarily mean your ISP can't interfere with your connection, some ISPs (depending of the laws in your country) use deep packet inspection and some even limit the bandwith for VPN. – Broco Sep 02 '16 at 09:59
  • Hello Broco, Thanks for taking the time for this. I just tried to send a file to the server. I experience pretty much the same behavior. It is as if the flow of data exists for something like 5 seconds and then it freezes for 5 seconds. Then it continues again for 5 seconds and it freezes for another 5. – Scudelari Sep 02 '16 at 13:25
  • About the ISP, it is true that it is possible but I don't really think this is the case. The server country is Brazil while the client is in Belgium. – Scudelari Sep 02 '16 at 13:26
  • Oh then you might have an even weirder issue I experienced once and was just able to find out because a friend of mine worked with a big ISP here in Germany. The problem you encounter may be the result of transit issues between tier 1 and tier 2 providers and thus the packets have to travel a longer and slower route than they should. You can inspect this by going through all the entries in your traceroute and see if the packets make way more hops than needed, especially when sending data between big providers and small providers across multiple countries. – Broco Sep 03 '16 at 22:20
  • Hello Broco, Thanks for input, but that doesn't seem to be the case. I tried to tracert to the server without VPN and it gives me just 9 hops. – Scudelari Sep 04 '16 at 17:11
  • If I then tracert with the VPN connected to the inner VPN addess, the tracert gets only one hop. – Scudelari Sep 04 '16 at 17:13
  • If I ping the server directly from the internet (no VPN) it takes the same as if I ping the inner VPN subnet. – Scudelari Sep 04 '16 at 17:14
  • Nothing? nobody? Noone? :( – Scudelari Sep 06 '16 at 11:32
  • Well if you experience the same issue with and without VPN this is obviously not a VPN issue. And of course you have less hops inside the VPN because you tunnel the connection. This is a connection issue so either one of the sites is misconfigured (you could try to send/receive data from/to another site than the ones you try) or the connection between the 2 sites is just slow/unstable, one reason for that could be what I wrote before. – Broco Sep 06 '16 at 16:26
  • I disagree. The problem is *clearly* not the ping, since the connection speed is high in the beginning of the transmission of the file. Please recall that the file transfers quite fast in the beginning but the speed falls very fast and then the transmission is made on "pulses". – Scudelari Sep 09 '16 at 11:09
  • Ping and bandwidth are 2 different things. And I didn't say ping was a problem, I said an unstable connection is and that it doesn't have anything to do with VPN if you experience the same behaviour with AND without VPN. – Broco Sep 09 '16 at 12:53

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