The rising popularity of live IPTV has triggered renewed interest in P2P multicast. In particular, the simple and robust 'swarming' style of P2P multicast is currently favored over more traditional tree-based approaches, which are seen to be complex and fragile. Swarming approaches, however, exhibit a basic control-overhead-versus-latency tradeoff that gears it more towards high-volume, latency-tolerant applications. This paper presents a new unstructured P2P multicast protocol called Chunkyspread that is tree-based yet simple and robust. Chunkyspread uses multiple trees to provide fine-grained control over member load, reacts quickly to membership changes, scales well, and has low overhead. This paper gives a detailed description of Chunkyspread and an apples-to-apples comparison with the DHT-based Splitstream multi-tree P2P multicast algorithm. We show that Chunkyspread exhibits far better control over transmit load than Splitstream, while exhibiting comparable or better latency and responsiveness to churn. This comparison establishes Chunkyspread as the 'best of breed' among tree-based P2P multicast algorithms, thus setting the stage for future comparisons with swarming-based approaches.
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