Video streaming service has gained more and more popularity in today's Internet. With increasing number of users and video quality, the Internet traffic for video streaming has increased dramatically. At present, most video streaming services utilize server-client model based on unicast. In a unicast system, the servers suffer from overload and lack of scalability with increased video traffic.Multicast has been considered as an efficient communication mechanism and the basis of a decentralized model. It has been proposed and implemented in video streaming service to overcome the drawbacks in unicast systems.In this work, a global multicast demonstrator for live video streaming is built to investigate how multicast can improve network efficiency. A series of experiments using the demonstrator are performed in real world Internet. The Internet traffic is measured and analyzed. The results show that multicast can reduce the load on servers and the traffic in network.