Figure 4-1
This illustration depicts the various layers of stack communication used in a client/server application connection. On the client side, from the top down, the stack is constructed with the following layers:

- Client Application (uses OCI)
- Presentation - TTC
- Oracle Net Foundation Layer
- Oracle Protocol Support
- Network Protocol (TCP/IP, TCP/IP with SSL, and Named Pipes)

On the server side, from the top down, the stack is constructed with the following layers:

- RDBMS(uses OPI)
- Presentation - TTC
- Oracle Net Foundation Layer
- Oracle Protocol Support
- Network Protocol (TCP/IP, TCP/IP with SSL, and Named Pipes)

The Oracle Net Foundation Layer and Oracle Protocol Support comprise the Oracle Net. Associated with the Oracle Net Foundation Layer on the client side is naming methods. Associated with Oracle Net Foundation Layer on both the client and server sides is security services.