We explore 'SAAR', a new architecture for overlay multicast: we factor out the control plane into a separate overlay that provides a single primitive: a configurable anycast for peer selection. This separation of control and data overlays has several advantages. Data overlays can be optimized for efficient content delivery, while the control overlay can be optimized for flexible and efficient peer selection. Several data channels can share a control plane for fast switching among content channels, which is particularly important for IPTV. And, the control overlay can be reused in multicast systems with different data plane organizations.
We designed and evaluated a decentralized control overlay for endsystem multicast. We implemented from scratch a single-tree, multi-tree, mesh-based and hybrid (push/pull) multicast system, all of which use the control plane's anycast primitive for data overlay neighbor acquisition.
We are currently understanding the impact of the dataplane structure (e.g. trees vs meshes vs hybrids) on the performance of p2p overlay multicast systems. Although prior research has described new protocol designs or compared complete systems, the inherent tradeoffs among different dataplane designs are not well understood. For instance, it is easy to confuse the performance of a particular system (e.g. tree based protocols) with the efficiency of the underlying control mechanisms used to maintain the dataplane structures.
Our primary goal is to do an apples-to-apples quantitative comparison of the different dataplane designs and understand their inherent tradeoffs. Factoring out the control plane effects using SAAR enables us to do so. We systematically evaluate streaming overlay design choices, and quantify the various tradeoffs. We subject them to different deployment scenarios (e.g. scale, churn, resource index, flashcrowds, control plane assumptions etc.), and identify which protocol is suitable for a given setting.
Our implementation of SAAR and the multicast dataplanes is built on top of FreePastry. The system can deployed in the Internet, be run in the PlanetLab, Emulab or Modelnet network testbed. Alternatively, the unmodified systems can also be executed on top of a discrete-event network simulator that comes with FreePastry by replacing the underlying wire transport layer with the simulator's transport layer.