In a multicomputer network, sending a packet typically incurs two costs: start-up time and transmission time. This work is motivated by the observation that most broadcast algorithms in the literature for the star graph networks only try to minimize one of the costs. Thus, many algorithms, though claimed to be optimal, are only so when one of the costs is negligible. In this paper, we try to optimize both costs simultaneously for four types of broadcast problems: one-to-all or all-to-all broadcasting in an n-star network with either one-port or all-port communication capability. As opposed to earlier solutions, the main technique used in this paper is to coristruct from a source node multiple spanning trees, along each of which one partition of the broadcast message is transmitted.
