VPN Overheads

[jonks]

I have set up site to site VPN connection over a 1mbit ADSL and i am wondering what sort of over heads i am likely to get. On each end of the ADSL i have a VSU unit which creates the VPN Tunnel. When i do a ping from end to end i am getting a higher response time when that that of a 64k ISDN. Although copying a file down is much quicker on the ADSL.

Is there any thing i can do to increase performance. The VSU units are running 3DES which STAC compression.

Also i here that upload and download speeds differ on ADSL. Our central site push traffic to our remote sites, is there any way i can make the VSU units connect so i can get most the bandwidth i can get out of the ADSL

Thanks in advance