Strange bandwith result with iPerf and OpenVPN

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FedericoCoppola
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Strange bandwith result with iPerf and OpenVPN

Post by FedericoCoppola » Sun Dec 05, 2021 4:14 pm

Hi all,
I deployed a very small OpenVPN server on Ubuntu Server VM.
I need to manage less than 5 VPN (at maximum) connection that never happen in the same time.

After OpenVPN deployment I did some iperf test. I noted a very strange result

iPerf3 test from Remote PC with IP 10.8.0.3 to OpenVPN server with IP 10.8.0.1 (VPN tunnel is UP, using OpenVPN subnet IP) bandwith: 2/3 Mbit
iPerf3 test from OpenVPN server with IP 10.8.0.1 to Remote PC with IP 10.8.0.3 (VPN tunnel is UP, using OpenVPN subnet IP) bandwith: 10Mbit

I do not understand the reason that generate different bandwith result.

Iperf reverse test with openvpn generate different result.

Remote PC Internet speed is 30Mbit Download/25Mbit Upload (LTE connection)
OpenVPN server Internet speed is FTTH 1Gbit Download/300Mbit Upload

Any suggestions?
Thanks a lot!

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TinCanTech
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Re: Strange bandwith result with iPerf and OpenVPN

Post by TinCanTech » Sun Dec 05, 2021 11:31 pm

FedericoCoppola wrote:
Sun Dec 05, 2021 4:14 pm
I do not understand the reason that generate different bandwith result.
The internet is not symmetrical.

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openvpn_inc
OpenVPN Inc.
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Re: Strange bandwith result with iPerf and OpenVPN

Post by openvpn_inc » Mon Dec 06, 2021 8:33 pm

FedericoCoppola wrote:
Sun Dec 05, 2021 4:14 pm
I deployed a very small OpenVPN server on Ubuntu Server VM.
I need to manage less than 5 VPN (at maximum) connection that never happen in the same time.

After OpenVPN deployment I did some iperf test. I noted a very strange result

iPerf3 test from Remote PC with IP 10.8.0.3 to OpenVPN server with IP 10.8.0.1 (VPN tunnel is UP, using OpenVPN subnet IP) bandwith: 2/3 Mbit
iPerf3 test from OpenVPN server with IP 10.8.0.1 to Remote PC with IP 10.8.0.3 (VPN tunnel is UP, using OpenVPN subnet IP) bandwith: 10Mbit

I do not understand the reason that generate different bandwith result.

Iperf reverse test with openvpn generate different result.

Remote PC Internet speed is 30Mbit Download/25Mbit Upload (LTE connection)
OpenVPN server Internet speed is FTTH 1Gbit Download/300Mbit Upload
It's really hard to say. LTE connections vary, rarely meeting their stated standards IME. What do you get without the VPN? If the non-VPN speeds are close to the VPN speeds, that's the issue. Try several times.

One possible issue is that openvpn version 2.x is a single-threaded application. If that core happens to be overloaded or missing AES-NI support, it could impact bandwidth. The solution to that, DCO (data channel offload) is in the openvpn3 client already and will be in the server in version 2.6.

Hope this helps, regards, rob0
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FedericoCoppola
OpenVpn Newbie
Posts: 8
Joined: Wed Aug 11, 2021 10:36 am

Re: Strange bandwith result with iPerf and OpenVPN

Post by FedericoCoppola » Sun Dec 12, 2021 3:47 pm

Hi,
unfortunally I can not try a complete test without VPN.
Anyway I am sure that this VM is missing AES-NI support.
I will try to use DCO as you suggested!

Thanks
Federico

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openvpn_inc
OpenVPN Inc.
Posts: 464
Joined: Tue Feb 16, 2021 10:41 am

Re: Strange bandwith result with iPerf and OpenVPN

Post by openvpn_inc » Wed Dec 15, 2021 5:45 pm

AES-NI support in a VM depends on having that support in the physical machine's CPU. On a Linux, the "aes" flag in /proc/cpuinfo means you have it. Any recent CPU should support this, but of course not all CPUs are recent.

regards, rob0
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Answers provided by OpenVPN Inc. staff members here are provided on a voluntary best-effort basis, and no rights can be claimed on the basis of answers posted in this public forum. If you wish to get official support from OpenVPN Inc. please use the official support ticket system: https://openvpn.net/support

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