1. A Mobile Agent Infrastructure for QoS Negotiation of Adaptive Distributed Applications Roberto Speicys Cardoso & Fabio Kon University of São Paulo – USP BRAZIL

2. 2 Outline Infrastructure for QoS negotiation Highly distributed environments Adaptive applications Based on Mobile Agents Topics Architecture Implementation Experimental results

3. 3 Motivation Multimedia applications and Ubiquitous Computing services require QoS Current research focus is not on QoS negotiation QoS negotiation is important Exchange of several messages High number of QoS configurations Must be effective

4. 4 Architectural Requirements Fundamental Scalable, flexible and complete But also... Light QoS monitoring process QoS specification ≠ Application code Admission control Negotiation and Re-negotiation Effective Secure

5. 5 Architectural Design Central monitoring management node (replicable) On each node (not every node) Monitoring component QoS enforcement system QoS broker QoS negotiation system Mobile agent server

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7. 7 Implementation Reuse systems and tools whenever possible Aglets Adaptation Framework DSRT QML Identify technology shortcomings when applied to ubiquitous computing

8. 8 Performance Monitoring Requirements Applications must be aware of system-level and application-level QoS Light monitoring process Framework for Dynamic Adaptation of Distributed Systems Applications subscribe to simple or compound events Central node contacted only when an event of interest happens

9. 9 QoS Enforcement DSRT Processing time and memory guarantees Runs on top of SunOS, IRIX, Linux and Windows QoS requirements specified using DSRT API calls Our architecture decouples specification and source code Same application may work with another QoS enforcement system

10. 10 QoS Definition QML used to avoid DSRT specification using API calls QDL Also good Too tied to QuO XML Easier to implement Too verbose Harder to understand by humans

11. 11 QML Definition Example type CPU_RT_PCPT = contract { period: decreasing numeric usec; peakProcessing_per_period: increasing numeric; }; idealProcessing = CPU_RT_PCPT contract { period = 40; peakProcessing_per_period = 30; }; idealProfile for mpeg_player = profile { require idealProcessing; };

12. 12 QoS Negotiation QoS levels change throughout time Resource sharing, component failure, peaks of utilization Applications need efficient means for QoS negotiation Our framework allows applications to Wait for best QoS offer or timeout and choose among the received replies Choose roaming strategy: Linear x Parallel

13. 13 Negotiation process 1. Application subscribes to events with the monitoring system 2. Monitoring system notifies application 3. Application requests a QoS negotiation 4. Negotiator agent reads specification, defines negotiation strategy and creates ProxyNegotiator agents 5. ProxyNegotiator travels to remote hosts to negotiate and send back results 6. Negotiator collects results and passes to application 7. Application choses the best QoS offer

14. 14 QoS Brokering One host may negotiate with many applications simultaneously Reservation concurrency problems One application may negotiate with many hosts simultaneously Resource starvation issues CORBA QoS Broker Reservation requests generates tickets Ticket required for reservation When ticket expires, broker releases resources

15. 15 Adaptation Support Applications should use the mobile agent paradigm Flexibility and adaptability benefits Two adaptation techniques: Migration and Cloning Migration allows application to move to hosts with better QoS offers Cloning enables applications to adapt gracefully to service usage bursts and valleys

16. 16 Sample Application Multimedia reflector ReflectorAglet Specifies QoS requirements Detects processing shortages Uses QoS negotiation system Adapts to QoS changes

17. 17 Tests Performed Goal: Evaluate scalability Estimate increase in execution time when negotiating with multiple hosts Linear and parallel roaming strategies Each test performed 5 times Considered time elapsed between event notification and aglet departure to new host

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19. 19 Future Work Evaluate the infrastructure with other distributed applications Develop more sophisticated QoS negotiation algorithms Evaluate infrastructure usage (in which scenarios to use it)

20. 20 Conclusions We presented a mobile-agent-based infrastructure for QoS negotiation Goal is to be an effective mechanism for QoS negotiation First results: QoS negotiation system scaled up well from 1 to 4 hosts Evaluating up to 8 hosts Mobile agents present many potential advantages Concept introduced 10 years ago, but technology not yet widespread Object orientation took over 20 years!

21. 21 Questions? Software available at www.ime.usp.br/~speicys (preliminary version) Thank you! www.ime.usp.br/~speicys