Figure 1-2
This illustration depicts a client/server application connection using Oracle Net. The client shows a communication stack. From the top down, the stack is constructed with the following layers:

The database server shows a communication stack. From the top down, the stack is constructed with the following layers:

The TCP/IP network protocol resides between the client and the database server.

During a connection, the client application communicates with the Oracle Net layer. In turn, Oracle Net communicates with the TCP/IP protocol, which passes the connection to the Oracle Net layer on the database server.