Optimal Multicast with Packetization and Network Interface Support

Modern networks typically limit the size of the largest packet for efficient communication. Thus, long messages are packetized and transmitted. Such networks also provide network interface support for nodes, which typically includes a coprocessor and memory, to implement the lower layers of the communication protocol. This paper presents a concept of smart network interface support for packetization and an optimal multicast algorithm for systems with such support. Two implementations of smart network interface, First-Child-First-Served (FCFS) and FirstPacket-First-Served (FPFS), are studied and compared. It is shown that the FPFS network interface support is more practical and efficient. Next, the components of multicast latency under FPFS implementation are analyzed by using a pipelined model. A concept of -binomial tree is introduced, and proved to be optimal for multicasting under the FPFS scheme. A method to construct contention-free binomial trees on contention-free orderings of the nodes is presented. For a 64-node system with irregular network, simulation results indicate that the optimal -binomial tree is upto 2 times better than the conventional binomial tree for a range of multicast set sizes and message lengths. Thus, these results demonstrate significant potential to be applied to current and future generation high performance systems including MPPs and NOWs, where network interface support for multicast is provided.