Compression not effective on routed VPN

[aristizb]

Hi,

I have configured a VPN using OpenVPN 2.2-beta5 on Ubuntu 8.04.

Two subnets are connected via routed VPN, and everything seems to be working fine. I enabled compression on both client and server using the comp-lzo directive, but it looks that I never get a benefit from it; when I monitor the traffic between the client and server nodes and I initiate a file transfer from a machine on the server side to a machine on the client side, there is no data compression.

To be more clear, I created a 1 GB file full of zeros, then I scp it, and I see that roughly 1GB travel across the VPN, am I missing something or is it probably a wrong configuration on my VPN nodes?

The LZO library was installed on both sides, and when I start the VPN service I can see that compression is enabled on the logs:

"Tue Mar 1 11:41:48 2011 192.168.7.5:47834 LZO compression initialized"

Any help is appreciated.


Juan.

[janjust]

you're scp-ing an empty file over a VPN - the problem is in the 'scp' : scp/ssh encrypts the file for you, even if it is full of zeroes. You'd use '-o Compression=yes' in scp for that.

Try measuing the performance using either 'nc' (to transfer the empty file) or using iperf, which you can also 'feed' the file full of zeroes.

[aristizb]

Thanks a lot for the clarification.

Now that I use nc to transfer files between the nodes I can see a sustainable difference.

For a 1GB file, the VPN traffic is ~100 MB.
For a 100 MB file, the VPN traffic is ~11 MB.


Regards,



Juan.