A mechanism is provided for managing a process-to-process inter-cluster communication request. A call from a first application is received in a first operating system in a first data processing system. The first operating system passes the call from the first operating system to a first host fabric interface controller in the first data processing system without processing the call. The first host fabric interface processes the call to determine a second data processing system in the plurality of data processing systems with which the call is associated, wherein the call is processed by the first host fabric interface without intervention by the first operating system. The first host fabric interface initiates an inter-cluster connection to a second host fabric interface in the second data processing. The call is then transferred to the second host fabric interface in the second data processing system via the inter-cluster connection.