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Multicast Protocols for Publish Subscribe Systems

Multicast Protocols for Publish Subscribe Systems. Ashwin R. Bharambe Hemamalini Manickavasagam. Outline. What is publish-subscribe ? Multicast in publish-subscribe systems Small Group Multicast Evaluation Methodology Results Conclusions. What is publish-subscribe ?. Publications.

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Multicast Protocols for Publish Subscribe Systems

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  1. Multicast Protocols for Publish Subscribe Systems Ashwin R. Bharambe Hemamalini Manickavasagam

  2. Outline • What is publish-subscribe ? • Multicast in publish-subscribe systems • Small Group Multicast • Evaluation Methodology • Results • Conclusions

  3. What is publish-subscribe ? Publications Subscription • Publishers produce events or publications • Subscribers register their interests via subscriptions • Network performs routing such that • Publications “meet” subscriptions • Publications get delivered to appropriate subscribers

  4. Why do we care ? • De-coupling between senders & receivers • Advantages • Permits heterogeneous components • Interoperability • Ideal for evolving software • Fits many applications • Stock tickers, instant messengers, etc. • Multiplayer games!

  5. Architectures • Centralized • Rendezvous point based • Core components • Routing of publications and subscriptions • Matching • Delivery of publications

  6. Efficient publication delivery • Publication needs to be delivered to some subsetof subscribers • Multicast! • Problem • Could be any subset • Exponential multicast groups! • How about the most naïve multicast strategy ?

  7. Small Group Multicast (SGM) • Idea • Send list of recipients along with every packet! • High overhead if list is large, but – • More efficient than maintaining multicast group, if list is usually small • Use Narada overlay as the backbone

  8. SGM+ • SGM might send data to uninterested people • Use Narada mesh to get a rough sense of direction • Use recursive unicast starting from the closest guy

  9. Evaluation methodology • Internet games as example of a publish subscribe system • Workload • Quake-II – real life traces hard to find • Introduced BOTs into Quake-II • Supposed to be human-like • Visibility “box” used as subscription

  10. Simulation Infrastructure • ns-2 all the way • Ported Narada simulator to ns-2 • Implemented SGM, SGM+ over Narada

  11. Results (1/2) • SGM overhead prop. to delivery group size • Hovers around 4.5 • Very high fraction of packets are routed through nodes who are not interested!

  12. Results (2/2) • Scaled with respect to Unicast • As group size increases, SGM+ performs better • Publication delivery group is usually small!

  13. Conclusions • SGM • Gives good resource usage • Low overhead since delivery group sizes in games are typically small • Well suited for games! • Need workloads for characterizing other publish-subscribe systems

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