Sonicwall Site to Site VPN question

Hi All,

I have a question regarding Sonicwall Firewall Site to Site VPNs. The scenario I am thinking of in particular concerns a PRO 1260 and a TZ150. I am designing a multi-site Windows 2003 Active Directory network and want to take advantage of having separate IP ranges for my

3 different physical locations. I want to have a Site to Site VPN as follows :

main site 172.24.x.x PRO 1260 connected to internet via ethernet / Data Centre branch1 172.22.x.x TZ150 as firewall connected to net via Netgear DG

632 ADSL modem in "modem mode" branch2 172.21.x.x as above

Firstly, will the site to site vpn route the traffic between the sites or will it bridge all sites as if it was one logical ethernet segment ?

Secondly, what are these two different technologies called ?

Thirdly, when I add the 3rd site will all networks be able to talk to each other and is it possible to limit what traffic goes through these vpns and to do rate limiting,etc ?

What technology does the site to site VPN use Ipsec or PPTP or is it a ssl-based vpn ?

Is there a better way to achieve a 3 site network spanned over the public internet in a secure fashion ?

Thanks in advance for your help.