Site-to-site VPN software
In addition to the protocol issue, another important consideration is how the VPN software will be implemented. You can purchase dedicated VPN gateway appliances. Most firewall appliances, such as the Cisco PIX, also include VPN functionality. Alternatively, software firewalls such as Microsoft’s ISA Server or Check Point can also be configured as site-to-site VPN gateways. Finally, Microsoft’s server operating systems also can be set up through Routing and Remote Access Services (RRAS) as VPN gateways.
For more information, check out: http://www.zdnetasia.com/insight/internet/0,39044877,39370540,00.htm
Thomas W Shinder, M.D.
MVP -- ISA Firewalls