Experience in offloading protocol processing to a programmable NIC

Offloading protocol processing will become an important tool in supporting our efforts to deliver increasing bandwidth to applications. In this paper we describe our experience in offloading protocol processing to a programmable gigabit Ethernet network interface card. For our experiments, we selected a simple RTS/CTS (request to send/clear to send) protocol called RMPP (reliable message passing protocol). This protocol provides end-to-end flow control and full message retransmit in the case of a lost or corrupt packet. By carefully selecting parts of the protocol for offloading, we were able to improve the bandwidth delivered to MPI applications from approximately 280 Mb/s to approximately 700 Mb/s using standard, 1500 byte, Ethernet frames. Using "jumbo", 9000 byte frames the bandwidth improves from approximately 425 Mb/s to 840 Mb/s. Moreover, we were able to show a significant increase in the availability of the host processor.