Can ISPs and Overlay Networks Form a Synergistic Co-existence?

Overlay networks are becoming increasingly popular for their ability to provide effective and reliable service catered to specific applications [1][2][3]. For instance, this concept has been used in peer-to-peer services like SplitStream, content delivery networks like Akamai, resilient networks like RON and so on. Overlay networks consist of a number of nodes (spanning one or many domains) that collaborate in a distributed application. One of the underlying paradigms of overlay networks is to give applications more control over routing decisions, that would otherwise be carried out solely at the IP layer. Overlay networks typically monitor multiple paths between pairs of nodes, and select the one based on its own requirements (e.g., delay, bandwidth, etc.). Allowing routing control to take place at both the application layer and the IP layer, could have profound implications on how ISPs design, maintain and run their networks. The architecture and protocols that carriers use to run their networks are based on assumptions about how their customers and traffic behave. It is possible that the approach used by overlay networks could call into question some of carriers’ assumptions thus rendering it more difficult for them to achieve their goals. In this paper, we identify some potentially problematic interactions between overlay and layer-3 networks. We raise a key question: Can overlay networks and underlying IP networks form a synergistic co-existence? Given the recent rise in popularity of overlay networks, we believe that now is the time to address these issues. We hypothesize that it could be problematic to have routing control in two layers, when each of the layers is unaware of key things happening in the other layer. ISPs may be unaware of which nodes are participating in an overlay and their routing strategy. Overlay networks are unaware of an ISP’s topology, load balancing schemes, routing protocol timer values, etc. We believe that ISPs need to clearly understand the implications of overlay network behavior.