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Introducing Net8

This chapter introduces Net8, and provides an overview of its main applications, features, and functionality. It contains the following sections:

• Net8 Overview

• Oracle Connectivity Overview

• Configuration Overview

• Connection Routing Capabilities

Net8 Overview

Net8 is the foundation of Oracle's family of networking products, allowing services and their applications to reside on different computers and communicate as peer applications. The main function of Net8 is to establish network sessions and transfer data between a client machine and a server or between two servers. Net8 is located on each machine in the network. Once a network session is established, Net8 acts as a data courier for the client and the server.

Figure 1-1 shows a client-to-server connection:

Figure 1-1 Basic Client-to-Server Connection

Network sessions are established with the help of a listener. The listener is a separate process that resides on the server whose responsibility is to listen for incoming client connection requests and manage the traffic to the server.

The listener brokers the client request, handing off the request to the server. Every time a client (or server acting as a client) requests a network session with a server, a listener receives the actual request. If the client's information matches the listener's information, the listener grants a connection to the server.

For environments where a large number of connections need to access the same service, Net8 offers a routing process called Oracle Connection Manager that resides on a machine separate from the client or server. For further information about Oracle Connection Manager, see "Connection Routing Capabilities".

Oracle Connectivity Overview

Net8 allows connections to various services, such Oracle databases, non-Oracle databases, gateways and external procedures (functions that can be called from PL/SQL code). As Oracle databases are the most common service, this section will focus on database services.

When an end user connects to a database service from across the network, a connect string identifies the service through a net service name. For example:

sql> CONNECT username/password@net_service_name

A net service name is able to access a service across the network by providing the network description information necessary to locate the service on the network. A net service name is resolved into the:

• network route to the service, including the listener location through a protocol address

• service name that is typically the global database name--a name comprised of the database name and database domain--used to identify the database service

The listener, through a protocol, accepts the client connection. It verifies the client information with the information it has received from the database service, as well as information it has stored in its own configuration file, LISTENER.ORA. If the information matches, a connection is granted.

Configuration Overview

Configuration is accomplished by creating a list of the net service names that map to services and addresses of listener destinations and configuring a naming method by which to resolve the net service name. A naming method is a method by which a net service name is resolved.

Net8 supports the several categories of naming methods. Wherever you choose to store your service names, Net8 offers tools to easily configure net service names.

• existing name resolution service

  Net service names may be stored via an existing IP address translation mechanism.

• client configuration file

  Net service names can be stored in a local configured file called TNSNAMES.ORA on each client and server in the network. Because the TNSNAMES.ORA can be configured on individual clients, it allows you to fine tune for a particular client's needs.

• an external naming service

  If a third-party naming service is already configured in your environment, Net8 supports storing net service name information in it to avoid additional configuration.

• centralized store

  Net service names and service addresses can be stored in a central directory of service addresses. This central store, called Oracle Names, is an Oracle-specific name service that maintains a central store of service addresses. When client applications request connections to servers using a simple name, the Net8 client contacts Oracle Names to resolve the service into a network address descriptor.

  Figure 1-2 shows:

  1. A database registering its service with an Oracle Names server.

  2. Client seeking to locate a service on the network by contacting an Oracle Names server to retrieve the network address.

  3. Clients then transparently connecting to the service:

Figure 1-2 Client-to-Server Connection through Oracle Names

For more information about choosing the place to store net service names, see "Resolving Net Service Names".

Connection Routing Capabilities

Net8 offers connection routing for environments where:

• a large numbers of users need to access a single service through a single protocol

• different protocols are installed on the client and server, making a typical connection fail

  Typical Net8 connections require the client and server to have the same protocol installed.

• control of client access to designated servers in a TCP/IP environment is required

Connection routing is supported by Oracle Connection Manager, through which client connection requests are routed to the server.

Figure 1-3 shows how client connection are routed to Oracle Connection Manager, which resides on a separate machine in the network:

Figure 1-3 Client to Server Connections through Oracle Connection Manager

See "Oracle Connection Manager Architecture", for further information.

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