Network interface multicast protocols for wormhole-based networks of workstations

Wormhole-routing high-speed local area networks (e.g., Myrinet), increasingly used to build high-performance Network of Workstations, do not usually provide hardware support to multicast communication, that must instead be implemented in software by sending several point-to-point messages. Network Interface protocols allow an efficient software implementation of multicast communication, but require flow control techniques (to avoid buffer overflows) that may lead to a severe performance degradation. In this paper we address the problem of designing reliable and efficient Network Interface multicast protocols. We propose a flow control technique that provides the basis for four multicast protocols, and we perform extensive simulations to characterize the impact that various factors (such as network topology, presence of unicast traffic, composition of multicast groups, etc.) have on their performance. Interestingly, our simulation experiments sometimes lead to observations that are in contrast with previous results. In particular, the most simple multicasting algorithms (e.g., separate addressing) may outperform sophisticated algorithms usually considered more effective, such as those based on spanning-trees.