Directory Service (2)
Directory Service is a collection of software that is used to store information about an enterprise. It generally consists of at least one directory server and one or more directory clients
DNS is an example of of a well-known client-server directory. Service (information limited to IP addresses and names)
A true directory service is used to store virtually unlimited types of information
Each e-mail system has its own directory system which maps user’s name to an e-mail address. These directories cannot exchange information
Problem: every enterprise is using too many directory services which do not share data between themselves (it is known as N+1 problem)