A network protocol for cluster computing

The Xpress Transport Protocol (XTP) is designed to support the types of data exchanges typically found in cluster computing applications. It provides all the classic functionality of a transport protocol, plus new services such as transport multicast, multicast group management, transport layer priorities, traffic descriptions for quality of service negotiation, rate and burst control, and selectable error and flow control mechanisms. XTP has wide interconnectivity because it operates over any network layer (IP, CLNP), any datalink layer (LLC, MAC), or directly on top of the AAL of ATM. In general, XTP avoids coupling policy with mechanism; XTP offers services but the user's application defines what communications paradigm is most appropriate for its particular environment. In spite of its richer functionality, XTP's reliable data transfer modes have performance characteristics similar to TCP and XTP's unacknowledged transfer mode has performance similar to UDP. Since XTP can run simultaneously with other transport protocols, and can run over whatever network layer (if any) is provided, it represents a low risk way to exploit the increased functionality required for cluster computing without sacrificing connectedness or interoperability.