The following illustrates the flow of communication in a federation scenario between a telecommunications company acting as the Identity Provider, and a ringtone provider company acting as the Service Provider.
In an Identity Provider-initiated single sign-on scenario, the Identity Provider is configured with specialized links to specific Service Providers. These links actually refer to the local Identity Provider single sign-on service and pass parameters to the service identifying the remote Service Provider. So instead of directly visiting the Service Provider, the user goes to the Identity Provider site and clicks on one of the links to gain access to the remote Service Provider. This triggers the creation of a SAML assertion that is subsequently transported to the Service Provider.