There are a number of noticeable differences between Kerberos versions 4 and 5:
Protocols used in Kerberos 4 and 5 differ.
Kerberos 5 supports forwardable, renewable, and postdateable tickets.
Kerberos 5 is network protocol-independent.
Kerberos 5 tickets can contain more than one network address.
Kerberos 5 supports cross-realm authentication.
Encryption algorithms other than DES can be used in Kerberos 5.
It should be noted that Kerberos 4 clients can communicate with a Kerberos 5 server, but Kerberos 5 clients cannot communicate with a Kerberos 4 server. Therefore, if you don’t have any existing systems that use Kerberos 4, start with Kerberos 5.