We propose Streamline, a two-layered architecture designed for media streaming in overlay networks. The first layer is a generic, customizable and lightweight protocol which is able to construct and maintain different types of meshes, exhibiting different properties. We discuss two types of overlay networks and explain how the first layer protocol builds these networks in a distributed manner. The second layer is responsible for data propagation to the nodes in the mesh by constructing an optimized diffusion tree. In order to cover the vulnerabilities of the diffusion tree, we propose a masking mechanism which enables the nodes to instantly switch to alternative data paths when necessary. Our simulations reveal that, the structure and properties of the underlying mesh are key to the performance of the system and Streamline can tolerate high node churn without degrading delivery rate.