Patent ID: 7555751

Claim:
A method for upgrading a system, the method comprising: ceasing to route user sessions from a call routing entity to any one of a first server and a second server, wherein the call routing entity is in communication with the first server and the second server; importing data from the first server to a third server, wherein the first server, the second server, and the third server are of a current version, and wherein a replication application is maintained between the first server and the second server; terminating the communication of the call routing entity with the second server and the first server, and enabling routing of user sessions to the third server by engaging the call routing entity in communication with the third server; upgrading the first server and the second server while running the current version of the third server; importing data from the third server into the first server; and terminating the communication of the call routing entity with the third server, and enabling routing of user sessions to the first server and the second server by engaging the call routing entity in communication with the first server and the second server.