Client to Server Connection

Services in a Windows NT cluster are exposed as virtual servers. Client Workstations believe they are connecting with a physical system, but are in fact, connecting to a service which may be provided by one of several systems. Clients create a TCP/IP session with a service in the cluster using a known IP address. This address appears to the cluster software as a resource in the same group as the application providing the service. In the event of a failure the cluster service will “move” the entire group to another system. In the simplest case, the client will detect a failure in the session and reconnect in exactly the same manner as the original connection. The IP address is now available on another machine and the connection will be quickly re-established - Note that in this simple case all information related to the original session is lost. This provides higher availability, but no fault tolerance for the service. Applications can use transactions to guarantee that the client request has been committed to the server database to gain fault tolerant semantics. Future releases may make this failover transparent and maintain the connection between the client and service.