Each realm must include a server that maintains the master copy of the principal database. This server is called the master KDC server. Additionally, each realm should contain at least one slave KDC server, which contains duplicate copies of the principal database. Both the master KDC server and the slave KDC server create tickets that are used to establish authentication.
The realm can also include a Kerberos application server. This server provides access to Kerberized services (such as ftp, telnet, rsh and NFS). If you have installed SEAM 1.0 or 1.0.1, the realm might include a Kerberos network application server, but this software was not included with these releases.