What is the Oracle Net stack communication architecture?

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What is the Oracle Net stack communication architecture?

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The Oracle Net software is comprised of certain communication layers (programs), collectively known as a stack, which enable clients and database servers to share, modify, and manipulate data. The stack architecture is based on the Open Systems Interconnection (OSI) model.

On the client side, from top to bottom, the stack is constructed with the following communication layers:

Client Application (uses Oracle Call Interface (OCI))

Presentation Layer (Two-Task Common (TTC))

Oracle Net Foundation Layer

Oracle Protocol Support

Network Protocol (TCP/IP, TCP/IP with SSL, and Named Pipes)

On the server side, from top to bottom, the stack is constructed with the following communication layers:

RDBMS (uses Oracle Program Interface (OPI))

Presentation Layer (Two-Task Common (TTC))

Oracle Net Foundation Layer

Oracle Protocol Support

Network Protocol (TCP/IP, TCP/IP with SSL, and Named Pipes)

These client/server communication layers are described as follows:

Client Application: During a session with a database, a client uses Oracle Call Interface (OCI) to interact with the database server. OCI is a software component that provides an interface between the client application and the SQL language that the database server understands.

Presentation Layer: If the client and database server are running on different operating systems, character set differences can occur. The presentation layer resolves any such differences. The presentation layer is optimized for each connection to perform character set conversion only when required.

The presentation layer used by client/server applications is Two-Task Common (TTC). TTC provides character set and datatype conversion between different character sets or formats on the client and the database server.

At the time of initial connection, TTC evaluates differences in internal data and character set representations and determines whether conversions are required for the client and server to communicate.

Oracle Net Foundation Layer: The Oracle Net foundation layer is responsible for establishing and maintaining the connection between the client application and database server as well as for exchanging messages between them. The Oracle Net foundation layer is able to perform these tasks because of a technology called Transparent Network Substrate (TNS). TNS provides a single, common interface functioning over all industry-standard protocols. In other words, TNS enables peer-to-peer application connectivity. In a peer-to-peer architecture, two or more computers (called nodes when they are employed in a networking environment) can communicate with each other directly, without the need for any intermediary device.

On the client side, the Oracle Net foundation layer receives client application requests and resolves all generic computer-level connectivity issues, including the following issues:

• The location of the database server or destination service


• Whether one or more protocols are involved in the connection


• How to handle interrupts between a client and a database server based on their capabilities

On the server side, the Oracle Net foundation layer performs the same tasks as it does on the client side. It also works with the listener on the server to receive incoming connection requests.

In addition to establishing and maintaining connections, the Oracle Net foundation layer communicates with naming methods to resolve service names. It also uses security services to ensure secure connections.

Oracle Protocol Support: Oracle protocol support layer is positioned between the Oracle Net foundation layer and the network protocol layer. It is responsible for mapping TNS functionality to industry-standard protocols used in client/server connections. This layer supports the following network protocols:

• TCP/IP


• TCP/IP with SSL


• Named Pipes

Network Protocol: All Oracle software in the client/server connection process requires an existing network protocol stack to establish the computer-level connection between the client and server computers for the transport layer. The network protocol is responsible for transporting data from the client computer to the database server, at which point the data is passed to the server-side Oracle protocol support layer.

RDBMS: Information passed from a client application across a network protocol is received by a similar communication stack on the database server side. The process flow on the database server side is the reverse of the process flow on the client side, with information ascending through the communication layers.

Instead of OCI, the database server uses Oracle Program Interface (OPI). For each statement sent from OCI, OPI provides a response. For example, an OCI request to fetch twenty rows would elicit an OPI response to return the twenty rows once the rows have been fetched.

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