There are multiple factors that may cause slow speed. Here is a guide to get the maximum Speed on VPN connection. Turbo VPN Speed!
http://parkfarmshoot.co.uk/2014/05/ 1- Change Protocols
Different Internet Service Providers support different protocols. If you are experiencing slow speed, switch between the protocols i.e. Madhyamgram PPTP, Dongguan L2TP and OpenVPN. Switching between the protocols also resolves the disconnection issue.
VPNShazam windows application use Automatic protocol by default. This connects to SSTP protocol if PPTP is blocked, which may drop the internet speed as well. If you get any issue in connecting PPTP or L2TP then make sure that both protocols are working fine on your internet connection.
Some routers keep PPTP, L2TP and IPSec pass through options disabled by default. Check your router for PPTP, L2TP and IPSec pass through options under Firewall / Security tab and enable them. Also some 3rd party Anti-virus firewalls blocks PPTP and L2TP. Allow PPTP and L2TP through your 3rd party Anti-virus firewalls.
Some popular European ISPs (Internet Service Providers) block PPTP Protocol. So, if you are from Europe and PPTP is not giving you a smooth connection then try switching to other protocols.
2- Turn off Firewall
Some Routers and 3rd party firewalls also cause speed and disconnection issues. Disable the Router / 3rdparty / Windows Firewall and check the connection stability and speed.
3- Select the Nearest/Closest Server
If you are located too far from a VPN server, you may not get maximum speed of that VPN server. This is because the network traffic may travel around the Earth from a user to a VPN server and then back to destination host.
Each protocol provides different level of security. PPTP is less encrypted protocol while L2TP and SSTP are encrypted at higher levels as they provide up to 256 bit encryption. When encryption increases, speed decreases.
5- Finally, speed depends upon your internet connection.
Follow the below mentioned steps to check your speed:
1. Disconnect VPN.
2. Visit www.speedtest.net
3. Select your location as the same as VPN server in the map. (For example: If you want to access a UK website, select UK from the Map to test speed from your location to UK without VPN.)
4. Test your internet connection speed.
5. Now connect to VPN.
6. Test your internet connection speed with same servers.