1. A common directory comprising: a directory service logic; a search index storage unit adapted to store subscriber search keys of all subscribers in a network; and a local profile storage unit adapted to store profiles of a portion of all subscribers in the network, the directory service logic being adapted to access subscriber profiles by interfacing with said search index storage unit and with said local profile storage unit, the stored subscriber search keys being automatically replicated at remote search index storage units associated with other common directories, and wherein the stored subscriber profiles are not automatically replicated at remote local profile storage units associated with the other common directories; wherein said directory service logic looks-up a specific subscriber profile by: sending a subscriber search key to said search index storage unit; receiving a local profile path and a last update URL from said search index storage unit; using the local profile path to send a request to read the specific subscriber profile stored within said local profile storage unit; receiving an indication that the specific subscriber profile is not stored within said local profile storage unit; using the last update URL to send a request to read the specific subscriber profile stored within one of said remote local profile storage units; receiving the specific subscriber profile from said one remote local profile storage unit; using the local profile path to have the specific subscriber profile stored within said local profile storage unit; and receiving an indication that the specific subscriber profile was successfully stored within said local profile storage unit.