Abstract:

This article presents a low level protocol and network interface architecture for low overhead communication in a distributed memory computing environment --- such as workstations and PCs connected via a high speed LAN. We use both sender information and destination information to demultiplex messages directly to where they are needed. The network interface filters incoming messages, separating data delivery from synchronization so as to enable the optimization of simple data delivery while leaving more difficult synchronization to the host processor. To perform this filtering the interface has a small set of simple operations and a small amount of state. We have designed an interface architecture called DART which specializes these ideas to ATM networks. We have built an in-kernel software implementation of this interface with stock workstation and ATM interface cards. This implementation currently achieves a best case application to application latency of 24.5 usec. With a hardware version of DART, we expect to achieve latencies of under 10 usec for a 155Mbps ATM LAN and under 3 usec for a 622Mbps ATM LAN in the workstation LAN environment.