Vpn connection limited?

I started a VPN connection, some time ago, a client to connect to our server. The connection works, the management software market but also the whole is really too slow.

The RAS connection that appears on the server is 28 kbit / s which seems super slow, given the capacity of broadband on both sides .. on the client VPN connection is displayed at 12 Mbit / s.
For info, I opened the ipsec and ports on the router PTPP

Do you have ideas and solutions to solve this problem?

Best regards.

Hi
How you use VPN solution?

Well I use remote access with Windows 2003 server and the client uses the connection vpn windows.

Ps: I just see the connection vary as real 28kbits / s 134kbits/s..