In this dissertation, we introduce a proposal for building an alternative group communication service that shifts the multicast support from core routers to end-systems. Our proposal, called Host Based Multicast (HBM), operates at application-level and provides an efficient multi-point data distribution service for one-to-many or many-to-many communications. With this approach end-hosts, dedicated servers and/or border routers automatically self-organize into an overlay distribution topology where data is disseminated. This overlay topology can be composed of both unicast connections and native multicast islands (e.g. within each site). Therefore it offers a group communication service to all hosts, even those located in a site that does not have access for any reason, to native multicast routing. HBM is a centralized solution, where everything, including group membership management and overlay topology creation, is under the control of a single Rendez-vous Point (RP). This book focuses on four key aspects: scalability, robustness, efficiency, and security.