How to diagnose the cause of slow VPN speed?

Question

VPN

We have a VPN server in the US, we connect to it via PPTP. Without vpn speedtest to US gives out 16-22 Mbps, and through VPN 2-5.
Can anyone tell me how to diagnose where the bottleneck is (link to US, hardware limitation, bad routing..)? I would be grateful for any help!

Answer 1

1. iperf will show the width of the channel between peers
2. speedtest from a remote server was not brought, it is also desirable to look
3. if this is a weak virtual machine, it is possible to turn off encryption (mppe), although I doubt it.

Answer 2

drive iperf between you and the VPN server.
The channel to the USA, of course, was a little more than completely dull. Even the Europe-US enterprise networks are so far dull.