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A ubiquitous and efficient multicast mechanism is essential to the success of large-scale group communication applications. Traditional IP Multicast is implemented at network layer on routers, achieving great transmission efficiency but also posing significant challenges to deployment. End-host Multicast moves multicast functionality to transport or application layer on end hosts to have minimal deployment barrier, but incurs performance penalty due to duplicate packet transmission and inefficient routing. Between them, there are a spectrum of other multicast schemes trying to make better trade-off between system performance and deployability. Nevertheless, the lack of ubiquitous multicast support on the current Internet hinders the development of multicast applications, which in turn reduces incentives for multicast deployment. In this dissertation research, we designed and implemented the Universal Multicast (UM) framework to provide ubiquitous multicast delivery service on the Internet. Unlike previous work, we do not implement multicast functionality at a fixed place in the network for a particular deployment stage; instead, UM is a general framework within which applications can be provided with IP Multicast delivery immediately, and infrastructure support for multicast can gradually spread from the network edges into the core. Therefore the trade-off between system performance and deployability is not fixed by the design, but can evolve over time driven by user demand for the service. Our approach is to build an end-host overlay to connect IP-Multicast ‘islands’ by adaptive unicast tunnels, and use native IP Multicast within each island. The design consists of three major components: Host Multicast Tree Protocol (HMTP) for inter-island routing, Host Group Management Protocol (HGMP) for intra-island management, and a user Agent implementing the functionalities on end hosts. UM takes full advantage of infrastructure support where available and utilizes End-host Multicast where needed. It is fully distributed, self-organized, and independent from underlying multicast routing protocols. We evaluated the system performance through simulation, implemented a prototype and tested with existing multicast applications.