Embodiments of the invention include a mechanism for explicit communication in a clustered multiprocessor system that supports low-latency, protected, user-mode, communication across the machine boundaries of a clustered multiprocessor. Data transport may be accomplished over persistent, unidirectional, point-to point connections, each of which may be embodied in a small amount of state at each end, along with a statically allocated per-connection memory buffer, which may be directly accessible to the transport mechanism at both ends of each notional link. System Memory protection may be afforded by operating system ("OS") facilitated allocation of both restricted control of the network interface, and responsibility for data transport, to an application thread that may execute in the context of the processor-managed virtual address space. Connection buffer protection may be afforded by restricting access to connection state to those entries associated with the currently controlling thread.