Scalable Multicast Routing: Tree Types And Protocol Dynamics Article Swipe
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· 2017
· Open Access
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· DOI: https://doi.org/10.25549/usctheses-c20-619273
· OA: W190036224
This thesis investigates issues of multicast routing in large scale wide area internetworks. The work is pursued along two dimensions: (1) evaluation of multicast distribution trees and algorithms; and (2) analysis of multicast protocol mechanisms. Multicast trees can be shared across sources or may be source-specific. Differences in tree types may lead to different data packet delivery qualities and different costs in terms of bandwidth. Inspired by interest in using shared trees for scalable multicast routing, we investigate the trade-offs among different algorithms and tree types. The trade-off in performance is shown with regard to both individual groups and aggregated effects of large number of groups. When both shared and shortest path trees are supported by a protocol, a brute force combination of mechanisms for these two tree types may create packet loops. The looping conditions are explored, and proofs presented for protocol systems that are loop-free. Three candidate multicast loop-prevention mechanisms are described and analyzed. Different multicast routing protocols support not only two different tree types, but also two different operating modes: dense mode and sparse mode. We examine the tradeoffs of the different modes and the dynamic behaviors when switching from shared to source-rooted shortest path trees (SPTs). Protocol Independent Multicast (PIM) is used as the reference protocol that provides a framework for this study. Ultimately, a truly scalable multicast protocol should be able to reduce the number of routing entries by either compressing the number of routing entries or by discarding idle entries. Four alternative mechanisms are investigated. Finally we consider what would be needed to apply the IP multicast model to other underlying technologies. A resequencer model is presented for multicast over ATM networks. The model was designed to solve the cell demultiplexing and VC (virtual circuit) depletion problems. Three methods are presented to implement a multicast resequencer. Their performance is evaluated through simulation.
