The requirement is to use a single Login page to authenticate access to multiple separate Web sites. For example, if there is a Login page that provides access to three separate Web sites and a user tries to access site01, then the user is taken to a common Login page. After being authenticated, the user can also access site02 and site03, without being required to log in for each domain.
The following figure shows the expected user behavior.
Figure 4. Single sign-on for multiple domains
The main constraint is that the various domains need to be deployed as Web applications running inside containers that are compliant to Servlet 2.3 or above.
