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Scribe An application level multicast infrastructure

Scribe An application level multicast infrastructure. Kasper Egdø and Morten Bjerre. Motivating Scribe: Tracking stock prices. Users wish to track the price of stocks Prices need to be broadcast Many stocks, many users Dynamic set of users and stocks Faulttolerant and decentralized.

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Scribe An application level multicast infrastructure

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  1. ScribeAn application level multicast infrastructure Kasper Egdø and Morten Bjerre

  2. Motivating Scribe:Tracking stock prices • Users wish to track the price of stocks • Prices need to be broadcast • Many stocks, many users • Dynamic set of users and stocks • Faulttolerant and decentralized

  3. Overview • Pastry: Object location and routing scheme used by Scribe • Scribe: An application level multicast infrastructure • Anycast: An application layer built using Scribe • Conclusion

  4. Quick Pastry • 128-bit node/object space • Prefix routing • Good locality • ”Short routes” property • Non-FIFO • deliver, forward, newLeafs

  5. What is Scribe? • Application level multicast infrastructure • Built ontop of Pastry • Scales well • Best effort delivery

  6. Group management • Rendezvous Point (RP) • Access control done at RP

  7. Creating a group (1100) 1111 0100 1100 1101 1001 Rendezvous Point (Pastry root) Group Creator creates Group 1100 0111

  8. Member management • Joining a group • Children table • Leaving a group • A multicast tree is created

  9. Joining a group 1111 0100 1100 1101 Join request 1001 Rendezvous Point (Pastry root) 0111 Joining member

  10. Leaving a group 1111 0100 Leave request 1100 1101 Leave request 1001 Rendezvous Point Member (Pastry root) 0111 Leaving member

  11. Multicasting 1111 0100 Message 1100 1101 Multicast down tree 1001 Rendezvous Point (Pastry root) 0111

  12. Maintaining the tree • Parent heartbeats check if nodes are alive • Children rejoin group if parent dies • RP state information replicated to leaf nodes

  13. Repairing the tree 1111 0100 Join request Join request 1100 1101 Rendezvous Point 1001 Failed Node (Pastry root) 0111

  14. Problems with Scribe • Best-effort delivery • No built-in protection of information • Possible concurrency problems

  15. More reliability • Number and buffer messages • Applications can choose to improve reliability • Encryption of messages

  16. Comparing Scribe and IP multicast • Scribe scales better and supports dynamic groups • Scribe nearly as efficient as IP multicast

  17. Application of Scribe • Anycast offers anycast and manycast

  18. Anycast Client B Scribe group Client A Resource offered

  19. Conclusion • Scribe is very good for large scale multicast • Easy to implement applications which use Scribe

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