Virtual distance: A generalized metric for overlay tree construction

Overlay multicasting enabled many new overlay and peer-to-peer applications such as P2PTV, large-scale content sharing, and live video streaming. Sensitivity of these applications differs against various network performance metrics such as delay, loss, or bandwidth. We propose a generalized method of calculating overlay trees to increase user-perceived quality of performance-sensitive applications. We define and use the concept of virtual distance for constructing overlay trees. Abstracting applications´ sensitivity to various performance metrics within the virtual distances, we aim to find the most appropriate parent for a peer according to the application´s purpose. Calculating the virtual distance based on different criteria, but without protocol modification, makes the overlay multicast protocol satisfy different quality expectations. We show by simulation experiments that the protocol automatically calculates overlay trees based on delay or loss, depending on which is more important for the application under consideration.