BRANCH OFFICE CONNECTIVITY

I have a central office with two remote branches, all three office have
internet connections.

How can I connect these three offices through the internet securely so
there can be easy transfer of data and remote admin between the offices?

Thx

Way I do it is I have a Sonicwall TZ170 at the home office and Sonicwall
TZ150's at the remotes. These appliances create a secure vpn tunnel from the
remote branches to the home office for networking. An added advantage is we
have vpn client licenses on the 170 so some of us, when on the road, can vpn
from the hotel [with internet access] to work via our laptops.