Logon-ticket SSO fails between two systems sitting in different domains. Which constraint did the landscape break?

In the service-provider-initiated SAML flow, how does the SAP Gateway server end up trusting a user it never authenticated directly?

Why can't Kerberos/SPNEGO SSO be used from outside the corporate network, and what is the workaround?

What makes Kerberos/SPNEGO attractive for intranet Fiori SSO, and what does it cost in setup effort?

What is SAML, and what does it communicate?

Trace an SAP logon ticket from the issuing system to the accepting system.

How does SAP logon ticket-based SSO work — where are tickets stored, and what must back-end systems do to support them?