Technical data

Configuring Multiple Middle-Tiers with a Load Balancing Router
Networking 4-5
4.3 Load Balancing Considerations
In a configuration where there is a pool of applications servers (called a resource pool),
and a pool of Single Sign-On servers, you’ll need to add a virtual IP address to the
load balancers (either software or hardware) then add pools to the virtual IP
addresses. The application server pool needs to have persistence specified. Often, this
is an active HTTP cookie setting in the software or hardware configuration page in the
load balancer. See your administrator or documentation for your load balancer.
With SSL, cookies are problematic because of how encryption works. Often, you’ll
need to use the SSL session ID to specify persistence in your load balancer. Chapter 5
of Oracle Application Server Portal Configuration Guide contains extensive information on
load balancing. Some of that information is presented in the following section.
4.4 Configuring Multiple Middle-Tiers with a Load Balancing Router
This section describes how you can set up multiple middle-tiers, front-ended by a load
balancing router (LBR) to access the same OracleAS Metadata Repository.
The purpose of a Load Balancing Router (LBR) is to provide a single published
address to the client tier, and front-end a farm of servers that actually service the
requests, based on the distribution of the requests done by the LBR. The LBR itself is a
very fast network device that can distribute Web requests to a large number of
physical servers.
Let us assume that we want to configure the multiple middle-tier configuration,
shown in Figure 4–1. In the example, we show OracleAS Web Cache on the same
machine as the Portal and Wireless middle-tier, although they can theoretically be on
different machines.
Figure 4–1 Multiple Middle-Tier Configuration with Load Balancer