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Explore the fusion of NM and ALM in IP multicast, addressing deployment issues and stability factors. Learn about push and pull approaches, overlay networks, and adaptation for congestion control.
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Scalable Reliable Multicast Architecture Wenjun Zeng Computer Science Department University of Missouri-Columbia
Hybrid IP Multicast and ALM • IP Multicast (NM) • Pros: bandwidth efficient, low delay, more stable • Cons: deployment issue, reliability/scalability issue • ALM: • Pros: super scalability • Cons: less bandwidth efficient, potential longer delay, unstable (high node dynamic) • Hybrid NM and ALM • Bridge between NM and ALM, e.g., hybrid tree construction • Adaptation • How about other issues (reliability, congestion control, etc)?
Push or Pull? • IP Multicast: • Push • ALM: • Tree-based approaches: push (e.g., End System Multicast) • More efficient • but has instability issue (and bandwidth underutilization) • Data-driven randomized approaches: pull (e.g., CoolStreaming) • No tree, simple, better suited for addressing reliability • but incur latency-overhead trade-off • Hybrid overlay: push and pull • E.g. tree-bone based • Hybrid NM and ALM? • IP multicast tree bone (push)? Address instability! • Overlay (tree or mesh) for other issues, e.g. scalable reliability?
Example:Reliability: IP Multicast Retransmission • Potential problems: • Reliability? • It is likely that retransmitted packets will go through same (probably congested) routes as the original packets, likely to experience congestion and loss too. (bottleneck problem) • Retransmitted packets may deteriorate the congestion. • Scalability? • In an IP multicast case, the retransmitted packets will be sent to all participants, wasting bandwidth. • Although separate unicast session can be used, it increases the load of the original sender.
Sender Rtx node Overlay rtx network (pull) Receiver IP Multicast network (push) Path Diversity Overlay Retransmission • To exploit path diversity, each client identifies a couple of “good” Retransmission Nodes in overlay.
Observations • A pull-based (data-driven) overlay architecture seems to have more flexibility in exploiting path diversity • to reduce theretransmission delay and • to avoid severely congested (bottleneck) path. • to provide load balancing • It may be built on top of the traditional IP multicast architecture, ALM architecture or some hybrid