Multicasting is an essential technology in applications like IPTV or online multiplayer gaming and has been studied extensively in different networks. In this article, we introduce a new performance criterion, called multicast gain, which can be used for computing multicast efficiency. We analyze multicast transmission for delivery of live TV channels in tree-based networks representing e.g., multicast trees, and determine the gain of subtrees and links in order to quantify the benefits of multicasting. We also define a threshold in order to identify cases in which unicasting might be preferable. We show that although multicasting can usually outperform multiple unicasting in terms of bandwidth usage, due to the inherent overhead in establishing and maintaining multicast connections, in special cases, using multiple unicast flows can be a better choice.
