If you prefer, you can refer to <<servlet-authentication-mechanisms,Authentication Mechanisms>> for concrete ways in which users can authenticate.
These sections focus on specific ways you may want to authenticate and point back at the architecture sections to describe how the specific flows work.
* xref:servlet/authentication/preauth.adoc#servlet-preauth[Pre-Authentication Scenarios] - authenticate with an external mechanism such as https://www.siteminder.com/[SiteMinder] or Java EE security but still use Spring Security for authorization and protection against common exploits.