Abstract — This paper studies multicast application overlay networks in a repeated-game framework. In these overlays, users have both the motivation and the means to alter their position in the overlay tree. We introduce a repeated-game model of user behavior that captures the practical tradeoff between a user’s short-term desire for quality and long-term desire for the network’s continued existence. We simulate overlay treeformation protocols with this model to study their robustness to selfish users. We show that this model can explain user cooperation and provide insight into how overlay systems scale in the absence of heavyweight mechanisms or identity systems. We also use the model to derive practical guidance on how to make multicast overlay protocols more robust to selfish users. I.

We discuss the design methodology used to achieve commercial-quality reliability in the Akamai content delivery network. The network consists of 15,000+ servers in 1,100+ networks and spans 65+ countries. Despite the scale of the Akamai CDN and the unpredictable nature of the underlying Internet, we seek to build a system of extremely high reliability. We present some simple principles we use to assure high reliability, and illustrate their application. As there is some similarity-in-spirit between our implementation and recent trends in the research literature, we hope that sharing our experiences will be of value to a broad community.