You can install multiple Fedlet instances at the Service Provider so that each Fedlet instance talks to a different Identity Provider. Or you can deploy a single OpenSSO Enterprise instance at the Service Provider.
If you want to install multiple Fedlet instances so that each Fedlet instance talks to a different Identity Provider, use caution with this approach. Consider the following example. A ringtone provider acts as a Service Provider and conducts business with multiple telecommunications companies. Each telecommunications company acts as its own Identity Provider. The Service Provider might have to deploy multiple instances of its Ringtone Application, each with its own Fedlet instance. Each Fedlet instance would communicate with a different telecommunications company Identity Provider. The result is that each Identity Provider would be using a different instance of the Ringtone Application.
Consider another example. The Fedlet is deployed on Sun Application Server, and the Fedlet home-directory is configured in the Application Server domain configuration file, domain.xml. So for each new Fedlet instance, a new Application Server domain must be set up, and an instance of the Ringtone Application must be deployed on this new Application Server domain. Now the Service Provider has to maintain two Application Server domains for the same Ringtone Application. This presents two possibilities. One possibility is that the same Ringtone Application is run on different ports for different Identity Providers. The second possibility is that the same Ringtone Application is run on the same port on different machines. This could also translate into different Ringtone Application URLs that each Identity Provider will use with the Service Provider. Or the Service Provider would have to implement some logic to route to the correct Ringtone Application based on the particular Identity Provider requesting it.