A method, system, and article of manufacture that provide latency hiding, high bandwidth message passing protocols used for data communication between nodes of a parallel computer system are disclosed. A source node transmits a request to send message to a receiving node. Prior to receiving a clear to send message, the sending node continues to send deterministically routed (or fully described) data packets to the receiving node, thereby hiding the latency inherent in the request to send--clear to send message exchange. Once the sending node receives the clear to send message, any remaining portion of the message may be sent using partially described packets which may be routed dynamically, thereby maximizing bandwidth.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with Government support under Contract No. B519700 awarded by the Department of Energy. The United States Government has certain rights in this invention.