Flocks: Evaluation of a QoS- and Content-Aware Overlay

Dynamic, large social events with concurrent activities, in which participants view, but also provide high-quality content to other visitors, pose one of many challenges to multimedia delivery. Distributing content in such a situation is difficult, and requires strong support from the underlying network, in order to quickly respond to changes in supply and demand. A Flock is a flexible overlay built in a self-organized, decentralized manner, relying on a simple interest-property concept. In this paper, we use Flocks to build large overlays that are both content- and Quality-of-Service (QoS) aware, and show how they adapt their structure dynamically, depending on interests in available QoS. We evaluate their performance under churn and large scale failures through extensive simulations, and practical experiments under Internet conditions on the Planet Lab, and present a selection of our results.