The increasing use of System Area Network (SAN) demands efficient communication to benefit of SAN features through a direct access to network resources and avoiding kernel intervention in communication path. Recently, a consortium composed by Microsoft, Compaq and Intel authored a new standard, the Virtual Interface Architecture (VIA), designed to reduce software overhead in data transfers. This paper describes the communication protocol proposed in order to allow a complete implementation of MPI based on VIA. This protocol is needed because the plain use of the two VIA data transfer models does not allow the implementation of MPI-based on VIA, due to the large number of MPI communication flavors. To validate the goodness of the proposed protocol, a new communication layer based on VIA has been introduced in the LAM/MPI suite. The reported results, referring to a software VIA implementation for Fast Ethernet networks, exhibits a significant reduction in latency time of LAM/MPI based on VIA with respect to the same library based on the TCP/IP protocol.