Oracle Net enables connections from traditional client/server applications to Oracle Database servers. Figure 1-1 shows how Oracle Net enables a network connection between a client and a database server. Oracle Net is a software component that resides on both the client and the database server. Oracle Net is layered on top of network Oracle protocol support, rules that determine how applications access the network and how data is subdivided into packets for transmission across the network. In Figure 1-1, Oracle Net communicates with TCP/IP to enable computer-level connectivity and data transfer between the client and the database.

Figure 1-1 Client/Server Application Connection

Description of "Figure 1-1 Client/Server Application Connection"

Specifically, Oracle Net is comprised of the Oracle Net foundation layer, which establishes and maintains connections, and Oracle protocol support, which maps the foundation layer technology to industry-standard protocols.

• Java Client Application Connections
  

Internet connections from client web browsers to an Oracle Database server are similar to client/server applications, except that the connection request goes to an application web server.

Figure 1-3 shows the basic architecture for web client connections, including a client web browser, an application web server, and an Oracle Database server. The browser on the client communicates with HTTP to the web server to make a connection request. The web server sends the request to an application where it is processed. The application then uses Oracle Net to communicate with the Oracle Database server that also is configured with Oracle Net.

Figure 1-3 Web Client Connections through Application Web Server

Description of "Figure 1-3 Web Client Connections through Application Web Server"

The basic components have the following characteristics:

• HyperText Transport Protocol (HTTP)

  HTTP provides the language that enables web browsers and application web servers to communicate.

• Application Web Server

  An application web server manages data for a website, controls access to that data, and responds to requests from web browsers. The application on the web server communicates with the database and performs the job requested by the web server.

• Web Client Connections Through Java Application Web Server
  
• Web Client Connections Without an Application Web Server
  

Each database is represented by one or more services. A service is identified by a service name, for example, sales.us.example.com. A client uses a service name to identify the database it must access. The information about the database service and its location in the network is transparent to the client because the information needed for a connection is stored in a repository.

The repository is represented by one or more naming methods. A naming method is a resolution method used by a client application to resolve a connect identifier to a connect descriptor when attempting to connect to a database service. Oracle Net Services offers several naming methods that support localized configuration on each client, or centralized configuration that can be accessed by all clients in the network.

For example, in Figure 1-6, a company has three databases that clients can access. Each database has a distinct service name, such as sales.us.example.com, hr.us.example.com, and mktg.us.example.com.

1. The client uses the repository to find the information it needs for sales.us.example.com.

2. After the client has the information it needs, it connects to the database.

Figure 1-6 Service Information Repository

Description of "Figure 1-6 Service Information Repository"

To manage large networking environments, administrators have to be able to easily access a centralized repository to specify and modify the network configuration. For this reason, the Oracle Net Services configuration can be stored in a LDAP-compliant directory server.

Support of LDAP-compliant directory servers provides a centralized vehicle for managing and configuring a distributed Oracle network. The directory can act as a central repository for all information about database network components, user and corporate policies, and user authentication and security, thus replacing client-side and server-side localized configuration files.

All computers on the network can refer to the directory for information. Figure 1-7 shows clients, Oracle Database servers, and other servers (such as application web servers) connecting to a centralized directory server.

Figure 1-7 Centralized Storage of Network Configuration with a Directory Server

Description of "Figure 1-7 Centralized Storage of Network Configuration with a Directory Server"

Networking elements for the Oracle Database server and clients are preconfigured for most environments. The Easy Connect naming method is enabled by default, and does not require a repository. Clients connect using the hostname of the database. As a result, clients and servers are ready to connect out-of-the-box using Easy Connect, giving users the benefits of distributed computing.

If you anticipate receiving a large number of connection requests for a listening process (such as a listener or Oracle Connection Manager) over TCP/IP, then Oracle Net enables you to configure the listening queue to be higher than the system default.

Before sending data across the network, Oracle Net buffers and encapsulates data into the session data unit (SDU). Oracle Net sends the data stored in this buffer when the buffer is full, flushed, or when database server tries to read data. When large amounts of data are being transmitted or when the message size is consistent, adjusting the size of the SDU buffers can improve performance, network utilization, or memory consumption. You can deploy SDU at the client, application web server, and database.

Tuning your application to reduce the number of round trips across the network is the best way to improve your network performance. If this is done, then it is also possible to optimize data transfer by adjusting the size of the SDU.

Considerations for Modifying the Size of the SDU

Modify the SDU size under the following situations:

• The data coming back from the server is fragmented into separate packets.

• You are on a wide area network (WAN) that has long delays.

• The packet size is consistently the same.

• Large amounts of data are returned.

Do not modify the SDU size under the following situations:

• The application can be tuned to avoid the delays listed in the adjacent column.

• You have a high speed network where the effect of the data transmission is negligible.

• Your requests return small amounts of data from the server.

Under certain conditions for some applications using TCP/IP, Oracle Net packets may not get flushed immediately to the network. Most often, this behavior occurs when large amounts of data are streamed. The implementation of TCP/IP itself is the reason for the lack of flushing, causing unacceptable delays. To remedy this problem, specify no delays in the buffer flushing process.

Oracle Net Services provides support for InfiniBand high-speed networks. InfiniBand is a high-bandwidth I/O architecture designed to increase communication speed between CPUs, server-side devices, and network subsystems. Oracle Net Services provides support for Sockets Direct Protocol (SDP). SDP is an industry-standard wire protocol intended for use between InfiniBand network peers.

SDP reduces the overhead of TCP/IP by eliminating intermediate replication of data and transferring most of the messaging burden away from the CPU and onto the network hardware. The result is a low-latency, increased bandwidth, high-throughput connection that reduces the amount of CPU cycles dedicated to network processing.

The communication between clients, including Oracle WebLogic Server or any other third-party middle-tier client, and Oracle Database 12c can take advantage of high-speed interconnect benefits. Oracle WebLogic Server includes Oracle TCP/IP support as part of its installation.

A driver installed on the Oracle WebLogic Server servers transparently converts TCP/IP support to SDP support. The SDP requests are then sent to an InfiniBand switch that processes and forwards the requests from the Oracle WebLogic Server servers to the database server.

Availability to the database is crucial for any network. You can configure multiple listeners to handle client connection requests for the same database service. This is beneficial in Oracle Real Application Clusters configurations, where each instance has a listener associated with it. Multiple listener configurations enable you to use the following features.

• Connect-time failover enables clients to request a different listener, usually on a different node, if the first listener fails.

• Client load balancing enables clients to randomize requests to the multiple listeners, usually on different nodes. These features can be used together or separately. Together, they ensure access to the database and distribute the load to not overburden a single listener.

Oracle Connection Manager can be configured to grant or deny client access to a particular database service or a computer. By specifying filtering rules, you can allow or restrict specific client access to a server, based on the following criteria:

• Source host names or IP addresses for clients

• Destination host names or IP addresses for servers

• Destination database service names

• Client use of Oracle Net Services security features

Figure 1-11 shows an Oracle Connection Manager positioned between three clients and an Oracle Database server. Oracle Connection Manager is configured to allow access to the first two clients and to deny access to the third.

Figure 1-11 Intranet Network Access Control with Oracle Connection Manager

Description of "Figure 1-11 Intranet Network Access Control with Oracle Connection Manager"

Although Oracle Connection Manager cannot be integrated with third-party firewall products, vendors can package it with their own products in a way that enables this product to serve as an application gateway.

In general, firewalls should be set to receive incoming requests, and allow outbound calls from Oracle Database. By defining filtering rules, you can limit access to the network.

Figure 1-12 shows an application gateway controlling traffic between internal and external networks and providing a single checkpoint for access control and auditing. As a result, unauthorized Internet hosts cannot directly access the database inside a corporation, but authorized users can still use Internet services outside the corporate network. This capability is critical in Internet environments to restrict remote access to sensitive data.

Figure 1-12 Internet Network Access Control with an Application Gateway

Description of "Figure 1-12 Internet Network Access Control with an Application Gateway"

It is important to deploy at least two Oracle Connection Manager firewalls or Oracle Net Firewall proxies in an Internet network environment in the event that one firewall goes down.

On the client side, applications communicate with Oracle Net foundation layer to establish and maintain connections. The Oracle Net foundation layer uses Oracle protocol support that communicates with an industry-standard network protocol, such as TCP/IP, to communicate with the Oracle Database server.

Figure 1-15 illustrates the communication stack on the client.

Figure 1-15 Oracle Net on the Client

Description of "Figure 1-15 Oracle Net on the Client"

The Oracle Database server side is similar to the client side as illustrated in Figure 1-16. A network protocol sends client request information to an Oracle protocol support layer, which then sends information to the Oracle Net foundation layer. The Oracle Net foundation layer then communicates with the Oracle Database server to process the client request.

Figure 1-16 Oracle Net on the Server

Description of "Figure 1-16 Oracle Net on the Server"

The Oracle Net foundation layer uses Oracle protocol support to communicate with the following industry-standard network protocols:

• TCP/IP (version 4 and version 6)

• TCP/IP with SSL

• Named Pipes

• SDP

Oracle protocol support maps Oracle Net foundation layer functionality to industry-standard protocols used in client/server connections.