1. People, technology, and operating methods
2. TCP session modelling

3. Being able to create and deploy the devices acting as dual-homes in a specific network 
4. Building logical networks that share the same physical infrastructure
5. Allowing DCOM traffic to cross the firewall
6. Tunneling the DCOM traffic through TCP and putting the external OPC Proxy in a DMZ
7. Using the OPC-UA security model