The Kerberos used in AFS (formerly known as the Andrew File System) was
developed from the Kerberos 4 papers, but before the protocol was
formalized.

As a result, AFS Kerberos uses the RX protocol for all communication between
the clients and database servers (which function as KDCs in Kerberos
termology)

The standard AFS clients that perform authentication discard the TGT after
they acquire an AFS service ticket. This means that you can't get tickets
for other services using your AFS token.

It is possible to use regular Kerberos instead of AFS Kerberos. For more
information, see Question 2.12.