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RUBI

RUBI. Adaptive Resource Discovery for Ubiquitous Computing. Cecilia Mascolo C.Mascolo@cs.ucl.ac.uk. Rae Harbird R.Harbird@cs.ucl.ac.uk. Stephen Hailes S.Hailes@cs.ucl.ac.uk. RUBI. R esource discovery for Ubi quitous computing Autonomic, encapsulating overarching adaptive process

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RUBI

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  1. RUBI Adaptive Resource Discovery for Ubiquitous Computing Cecilia Mascolo C.Mascolo@cs.ucl.ac.uk Rae Harbird R.Harbird@cs.ucl.ac.uk Stephen Hailes S.Hailes@cs.ucl.ac.uk

  2. RUBI • Resource discovery for Ubiquitous computing • Autonomic, encapsulating overarching adaptive process • Few assumptions are made about the network environment • Operational over a wide range of network conditions

  3. Outline • Ubiquitous computing and resource discovery • Review of existing protocols • RUBI, design and evaluation • Future work • Conclusions and questions

  4. Ubiquitous Computing • Weiser’s vision becoming reality • 250 million microprocessors sold monthly, < 2 % destined for PCs • Ubicomp revenue • Provision of novel services, low / no ROI from connectivity alone • Environmental implications • Huge heterogeneity, immense scale, dynamic operation and volatility

  5. Communications Paradigm

  6. Communications Paradigm

  7. Previous Work • Global, central index of resources • Jini • Global, distributed index • Distributed hash tables • Resources discovered as needed • Konark, UPnP, SLP • Resource discovery based on ad hoc routing protocols

  8. Proactive Resource Advertisement

  9. Proactive Resource Advertisement

  10. Proactive Resource Advertisement

  11. Requests & Replies

  12. Reactive Resource Requests & Replies

  13. Reactive Resource Requests & Replies

  14. Reactive Resource Requests & Replies

  15. Reactive Resource Requests & Replies

  16. Varying level of node mobility

  17. RUBI • RUBI based on two routing algorithms: • proactive (OLSR) and reactive (AODV) • Assumptions: • IP level connectivity over any type of wireless link • Assume nodes can create or obtain an IP address • Operates at the network layer or at the application layer

  18. Algorithm Selection • How does a node determine the type of region it belongs to? • Link duration is used as a mobility feedback mechanism • Neighbour establishment used to assess stability of local links • Select routing algorithm based on perceived stability • Proactive algorithm: stable enough to elect relay nodes • Reactive algorithm: in all other cases

  19. Proactive Request to Reactive Region

  20. Proactive Request to Reactive Region

  21. Response Implosion • Problem: • A large number of replies may be returned to the source of the query • Solutions: • Introduce delay for nodes on the reply path • Wait for a period and evaluate replies received before sending one onwards • Evaluation can be difficult • Use request cancellation message from source when reply received

  22. Ensure Loop Free Operation • Problem • For composite requests, a node may satisfy only part of it • Will forward a request for remaining (unfulfilled) resources • Must ensure that new request is not processed by nodes that have already seen it • Solution • Preserve original message ID

  23. Experiment Design • Choose simple scenarios to test different aspects of protocol behaviour • Fixed characteristics • Network size, density • Relative node mobility • Mobility model • Node: Bandwidth, Power, Speed • Varying characteristics • Cache size and caching period • Request rate

  24. Measuring Performance • Request success rate • Protocol message overhead per resource request • Latency of replies • Showing where congestion exists in the network • Amount of state maintained per node • Request path length • Number of hops a query must traverse in order to obtain a response

  25. Discussion • RUBI represents trade-off between: • Context-aware operation • Efficiencies gained by assuming stability • Greater overhead than some approaches reviewed • Neighbour establishment and monitoring • More suitable for ubiquitous computing • Adaptive in an uncertain network environment

  26. Conclusions • Resource discovery • Key factor in realisation of ubicomp vision • RUBI designed with ubicomp environment in mind • Routing algorithms ensure the efficient dissemination of information • Autonomously adapts using locally obtained information • More suitable than other ‘single algorithm’ approaches

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