Since CAS version 4.0, in addition to the server support, a new CAS client support is available in the CAS server through the cas-server-support-pac4j module. It means that the CAS authentication can be delegated to another CAS server.
The CAS 1.0 and 2.0 protocols are enabled out of the box with the CAS release. For more information on the CAS protocol, please see the protocol document.