However, in many multi-building installations where a central control capability is de- sired, or where there is some outlying equipment to monitor, it is more and more com- mon to connect the separate BCS networks using existing cables and IP protocol. This connection may be entirely confined behind a corporate firewall, but more likely includes the public Internet . How are such network connections secured? If they are secured, it is most commonly done by using virtual private networking (VPN) technology from build- ing firewall to building firewall across the Internet . A router implementing this technol- ogy takes BCS traffic at one end-node,.
