Failover Options in the Public Network Infrastructure

The network used to access Oracle Internet Directory services is called the Public Network Infrastructure. Providing network level load balancing and failover measures (connection re-direction) in the Public Network Infrastructure are highly recommended since these measures provide a high degree of flexibility and transparency to the application clients.

If the Oracle Internet Directory services are accessed from the Internet, this would include a couple of high speed links (T1 to T3) and an intelligent TCP/IP level connection re-director. If the Oracle Internet Directory services are accessed from an Intranet, this would include high speed LAN connections to the server computers running the Oracle directory server and an intelligent TCP/IP level connection re-director. In both cases, there would be more than one computer serving LDAP requests so that failure of one Oracle directory server computer would not affect availability.

Figure 26-2 illustrates a typical Internet deployment of Oracle Internet Directory with network-level failover enabled.

Figure 26-2 Network-Level Failover

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In Figure 26-2, the Oracle directory servers (LDAP servers) can be connected to either the same back-end database or different back-end databases. In this deployment, network-level connection redirection can be accomplished by both hardware and software solutions.

This section contains these topics:

• Hardware-Based Connection Redirection

• Software-Based Connection Redirection

Hardware-Based Connection Redirection

Hardware-based connection redirection technology is available from several vendors. These redirection devices connect directly to the Internet and can route requests among several server computers. They can also detect computer failures and stop routing requests to the failed computer. This feature guarantees that new connections from clients will not be routed to a failed computer. When a computer comes back, the device detects it and starts routing new requests to it. These devices also perform some load balancing, which makes sure that client requests are uniformly distributed.

Some of the vendors providing hardware based re-direction technologies are:

• Accelar Server Switches from Nortel Networks

• Local Director from Cisco

• BIG/ip from F5 Labs Inc.

• Hydra from HydraWEB Technologies

• Equalizer from Coyote Point Systems

Software-Based Connection Redirection

The software-based solutions essentially work in the same manner as their hardware counterparts. Some of the currently available solutions include Dispatch from Resonate and Network Dispatcher from IBM.