Heimdal is a free implementation of Kerberos 5. The goals are to: * have an implementation that can be freely used by anyone * be protocol compatible with existing implementations and, if not in conflict, with RFC 4120 (and any future updated RFC). RFC 4120 replaced RFC 1510. * be reasonably compatible with the M.I.T Kerberos V5 API * have support for Kerberos V5 over GSS-API (RFC1964) * include the most important and useful application programs (rsh, telnet, popper, etc.) * include enough backwards compatibility with Kerberos V4