Initial and Pass Through Authentication Using Kerberos V5 and the GSS-API (IAKERB)
This document defines extensions to the Kerberos protocol and the GSS-API Kerberos mechanism that enable a GSS-API Kerberos client to exchange messages with the KDC using the GSS-API acceptor as the proxy, by encapsulating the Kerberos messages inside GSS-API tokens. With these extensions a client can obtain Kerberos tickets for services where the KDC is not accessible to the client, but is accessible to the application server.