Oracle Integration Cloud (OIC) provides a comprehensive solution for integrating applications within the cloud and on-premises. When it comes to on-premises integration, there are a few key options for connectivity to ensure secure and reliable communication. Here’s a look at some of the main methods:

1. Oracle Integration Cloud Service (ICS) Agent: Oracle offers an on-premises agent that you can install within your local environment. The agent facilitates the communication between Oracle Integration Cloud and on-premises systems, securely bridging the connection between cloud and local resources.

2. VPN Connection: A Virtual Private Network (VPN) connection provides a secure tunnel between your on-premises network and the Oracle Cloud. This can allow for encrypted communication and secure data transfer.

3. Fast Connect: Oracle Fast Connect provides a dedicated, private connection between your on-premises network and Oracle’s cloud. It offers higher bandwidth and a more reliable connection compared to a VPN over the internet.

4. REST/SOAP Web Services over HTTPS: For some integrations, it may be possible to expose on-premises services using standard web service protocols like REST or SOAP, and secure them using HTTPS. This can provide a way to interact with on-premises systems without needing to set up more complex connectivity options.

5. Hybrid Solutions: In some cases, a combination of these methods might be used to provide a comprehensive and flexible integration solution. The best approach will depend on specific requirements like performance, security, compliance, and so on.