The "On-Net" option is a roaming option that the Organization can enable on a group of Locations to create a federated network.
When users register in a Location belonging to the federated network, they can access any other Location of the federated network using his original account, without registering again.
The Locations on the federated network may have different internet access policies. When visiting another Location on the federated network, the users will inherit the policies provisioned on his account durign the registration in the original Location.