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Distributed Mobile Event Systems

Distributed Mobile Event Systems. Sasu Tarkoma 30.11.2004 MiNEMA Workshop. Contents. Introduction Motivation, Challenges Mobile Event Systems Fuego Event Service Content-based Routing Mobility support Conclusions. Introduction.

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Distributed Mobile Event Systems

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  1. Distributed Mobile Event Systems Sasu Tarkoma 30.11.2004 MiNEMA Workshop

  2. Contents • Introduction • Motivation, Challenges • Mobile Event Systems • Fuego Event Service • Content-based Routing • Mobility support • Conclusions

  3. Introduction • Event-based systems are a good candidate for mobile and wireless environments • Asynchronous, anonymous one-to-many communication • Expressive semantics with filters • Content-based routing and addressing • Primitives: adv, unadv, sub, unsub, pub • Subscription-semantics • Subscriptions are propagated throughout the system, notifications are sent on the reverse path • Advertisement-semantics • Advertisements are propagated throughout the system, subscriptions on the reverse path, notifications on the reverse path of subscriptions

  4. Challenges • How to cope with mobile users? • Disconnected operation • Buffering and queue management • Mobile subscribers / producers • Handover protocol for relocating subscriptions and updating the topology • Multiple indirection points • How to manage large numbers of filters? • Covering relations, filter merging • Efficient routing algorithms are needed • General requirements • fast convergence of the subscription topology • mobility-safety: no false negatives and positives

  5. Mobility-aware Systems • Recently, mobility protocols and extensions have been proposed for different pub/sub systems: • Trivial solution is to used flooding (topology update) • Jedi • Hierarchical topology, move-in and move-out commands, mobility not main focus • Elvin • Centralized proxy for supporting disconnected operation, no roaming between proxies • Siena • Generic mobility service on top of the pub/sub layer • Relies on ping/pong synchronization and has a high cost in terms of latency and exchanged messages • Rebeca • Acyclic graph topology with advertisements

  6. Fuego Event System • Scalable distributed event framework for mobile computing • The Fuego event router consists of two parts: • access server functionality with buffering and handover support for mobile clients, and • extensible routing core for distributed operation • New data structures for efficient content-based routing: • poset (partially ordered set)-derived forest • weakly merging forest • the forest is considerably more efficient than dag (directed acyclic graph) - based structures • Rendezvous-based mobility support for fast handovers and subscription topology updates • RP or paths to RP are updated instead of the whole topology

  7. Mobility Architecture 1. End-point change to mobile (User-mobility) 2. Access server handover (terminal-mobility) AC AC Desktop AC AC AC Event Domain A Event Domain C TOPOLOGY UPDATE AC AC 3. Handover between domains (terminal-mobility) Event Domain B Desktop AC AC 4. End-point-change (different access server) AC

  8. Demonstration at WMCSA 2004

  9. Conclusions • In order to develop flexible systems we have divided the event router into two parts: access part and the routing part • A router may support several routing and mobility protocols • The topology update and synchronization between access servers is costly in pub/sub mobility • We propose a rendezvous-based mobility protocol • Rendezvous points may be updated efficiently • It is possible to leverage overlay systems, such as Hermes, for scalability • Efficient algorithms are crucial for content-based routing • The poset-derived forest and variants, filter merging • Future and current work: federation, load balancing

  10. Related Publications • Sasu Tarkoma, Jaakko Kangasharju, Kimmo Raatikainen. Client Mobility in Rendezvous-Notify. International Workshop for Distributed Event-Based Systems (DEBS03), in conjunction with the ACM SIGMOD/PODS Conference, San Diego. Available at ACM Digital Library. • Sasu Tarkoma. Distributed Event Dissemination for Ubiquitous Agents. Proceedings of the 10th ISPE International Conference on Concurrent Engineering (CE-2003), Madeira, Portugal. Pages 105-110. • Sasu Tarkoma. Event Dissemination Service for Pervasive Computing. Pervasive 2004 Doctoral Colloquium, 18-19.4. 2004 Linz/Vienna, Austria. • Sasu Tarkoma and Jaakko Kangasharju. A Data Structure for Content-based Routing. Accepted for publication in the IASTED International Conference on INTERNET AND MULTIMEDIA SYSTEMS AND APPLICATIONS (EuroIMSA 2005), February 21-23, 2005, Grindelwald, Switzerland.

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