This diagram is divided into the following four sections, from top to bottom.
Public: This represents external access to Oracle Collaboration Suite. Users can connect through a NAT layer using HTTP, HTTPS or SMTP.
DMZ: The demilitarized zone between the outside world and Oracle Collaboration Suite; it contains one network services server running Reverse Proxy for ports 80 and 443, an SMTP relay on port 25 and DNS BIND on port 53. Outside traffic sees 12.34.56.* IP addresses, while internal users will see 10.10.10.* addresses or 12.34.56.* addresses, depending on how DNS is configured.
Internal: The internal network, with all three tiers installed on the same server.
Customer Network: Internal users are routed through the DMZ because there is only one DNS server.