The image shows an OCI region, and a user outside the OCI region.
The user sends DNS queries to the Oracle Cloud Infrastructure DNS service, and the service sends responses back to the user.
Users send requests to different internal and external environments:
Each environment has it's own load balancer within a virtual cloud network, inside a service subnet. Requests are routed through the respective load balancers to worker nodes inside a pod network. For example, requests sent to the development environment (dev.myapp.org) are sent to the dev pods. There are also test and production pods inside the pod network.