Acronym for Novell Directory Services.
A highly scalable, high performance, secure directory service created by Novell. It can store and manage millions of objects, such as users, applications, network devices, and data. It is used to control access to network resources and build relationships between them. NDS eDirectory natively supports the directory standard LDAP version 3.
I have personally seen a demo of NDS with 20 replicas and over one billion objects in the tree.