  All-to-all data transmission is a typical data transmission pattern in
blockchain systems. Developing an optimization scheme that provides high
throughput and low latency data transmission can significantly benefit the
performance of those systems. In this work, we consider the problem of
optimizing all-to-all data transmission in a wide area network(WAN) using
overlay multicast. We prove that in a congestion-free core network model, using
shallow broadcast trees with heights up to two is sufficient for all-to-all
data transmission to achieve the optimal throughput allowed by the available
network resources.
