This paper introduces DONet, a data-driven overlay network designed for live media streaming. DONet simplifies the overlay structure by allowing nodes to exchange data availability information and dynamically forward data according to availability, rather than maintaining a complex global structure. Key features include ease of implementation, efficiency, and robustness. The authors propose a scalable membership and partnership management algorithm, along with an intelligent scheduling algorithm, to ensure efficient and continuous streaming with low control overhead. Extensive experiments on the PlanetLab testbed demonstrate that DONet achieves high streaming quality, low transmission delay, and minimal control overhead, even under challenging network conditions. A public implementation, CoolStreaming, was released and has been used to broadcast live sports programs, attracting over 30,000 unique users and supporting more than 4,000 simultaneous connections. Initial results show that the current internet has sufficient bandwidth for TV-quality streaming, and larger overlays generally deliver better streaming quality. The paper also discusses the design and performance evaluation of DONet, comparing it with tree-based overlays and addressing practical challenges.This paper introduces DONet, a data-driven overlay network designed for live media streaming. DONet simplifies the overlay structure by allowing nodes to exchange data availability information and dynamically forward data according to availability, rather than maintaining a complex global structure. Key features include ease of implementation, efficiency, and robustness. The authors propose a scalable membership and partnership management algorithm, along with an intelligent scheduling algorithm, to ensure efficient and continuous streaming with low control overhead. Extensive experiments on the PlanetLab testbed demonstrate that DONet achieves high streaming quality, low transmission delay, and minimal control overhead, even under challenging network conditions. A public implementation, CoolStreaming, was released and has been used to broadcast live sports programs, attracting over 30,000 unique users and supporting more than 4,000 simultaneous connections. Initial results show that the current internet has sufficient bandwidth for TV-quality streaming, and larger overlays generally deliver better streaming quality. The paper also discusses the design and performance evaluation of DONet, comparing it with tree-based overlays and addressing practical challenges.