Which VPN solution is best Practice

Hello All

With all the options out there for linux, IPSec, PPTP, SSL Tunnel etc
Which is best "safest" free vpn to use.

I want to be able to link mulitple satelite offices to a head office, where
they will connect to a central server for services.

Each office will have ADSL connecting to the internet and Dynamic IP
addresses, although I can use dynamic update client to make sure the domain
name for each site gets updated as the ip changes. 
So that is probably a consideration for the choice, needs to support domain
name and not ip address.

Thanks
Stu

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