## Kerberos Names

A Kerberos name contains three parts. The first is the principal name, which is usually a user's or service's name. The second is the instance, which in the case of a user is usually null. Some users may have privileged instances, however, such as "root" or "admin." In the case of a service, the instance is the name of the machine on which it runs; i.e. there can be an rlogin service running on the machine ABC, which is different from the rlogin service running on the machine XYZ. The third part of a Kerberos name is the realm. The realm corresponds to the Kerberos service providing authentication for the principal. For example, at MIT there is a Kerberos running at the Laboratory for Computer Science and one running at Project Athena.

When writing a Kerberos name, the principal name is separated from the instance (if not null) by a period, and the realm (if not the local realm) follows, preceded by an "@" sign. The following are examples of valid Kerberos names:

billb

jis.admin

srz@LCS.MIT.EDU

treese.root@ATHENA.MIT.EDU