In this paper, we propose a new approach, Simple Explicit Multicast (SEM), which uses an efficient method to construct multicast trees and to deliver multicast packets to all destinations. In order to construct a multicast tree, the source encodes the list of destination addresses in a branch message. This message discovers the tree branching routers and creates a multicast routing state in each of these routers. For multicast packets delivery, it uses recursive unicast trees where packets travel from a branching router to another following the tree constructed by the branch message. q