Wormhole routing LANs are emerging as an effective solution for high-bandwidth, low-latency interconnects in distributed computing and cluster computing applications. An important example is the 640 Mb/s crossbar-based Myrinet. A key property of conventional LANs, which is valuable for many distributed applications, is transparent, reliable network-level multicast. It is desirable to retain this property also in wormhole LANs. Unfortunately, efficient, reliable multicasting in wormhole LANs is

more »

... roblematic because of the potential for deadlocks. As a consequence, current multicasting implementations typically consist of repeated unicast or assume a priori buffer reservations. These solutions, however, tend to increase latency and do not scale well. In this paper we address the problem of providing transparent, reliable, efficient network level multicasting in the wormhole LAN. We describe several protocols for achieving deadlock-free, reliable multicasting using restricted routing and fast buffer reservation techniques. Tradeoffs involving complexity and performance of various solutions are discussed, and are illustrated using simulation. A simple multicast implementation for Myrinet has been carried out, and experimental results are presented.