A knowledge base article about What is CalNet Central Authentication Service (CAS)? provided by the UC Berkeley IT Service Hub - Knowledge Portal
CalNet CAS, the Central Authentication Service, is a central facility providing CalNet Kerberos web proxy authentication on behalf of cooperating web applications and web servers. CAS is the UCB implementation of the Apereo Central Authentication Service which was originally developed at Yale.
For a technical overview of CAS, please see the CAS Overview section of the CalNet website.