Kerberos is based on a variant of Needham-Schroeder that is named for the multi-headed dog that guarded the entrance to Hades. V5 has more overhead than V4, uses OSI ASN.1 (Abstract Syntax Notation 1) for describing data types, is not DES dependent (like V4), and supports multiple realms. It also has longer ticket lifetimes, allows for renewal of tickets, and will issue postdated tickets.