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Expert Topic for 1770

This article discusses the key technical issues and limitations of DRE systems and explores how component middleware can address these limitations through QoS provisioning. It covers topics such as static and dynamic QoS provisioning, the limitations of distributed object computing (DOC), and the use of component middleware to overcome these limitations. The article also introduces the QuO framework for specifying and managing QoS requirements in DRE systems.

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Expert Topic for 1770

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  1. Expert Topic for 1770 QoS-Enabled Middleware Reza Eftekhari

  2. Content • Introduction • Key Technical issues for DRE • Component Middleware • Limitation of DOC • Static QoS Provisioning • Dynamic QoS Provisioning • Conclusion Reza Eftekhari

  3. Introduction • COTS (Commercial off-the-shelf) middlewares: CORBA, RMI, COM+ • Business-oriented QoS requirements: • Data persistence, confidentiality, and transactional support. • DRE (Distributed Real-time Embedded) systems: • Processor allocation, network latency, jitter, bandwidth Reza Eftekhari

  4. Key Technical issues for DRE • Reducing the complexity of managing large-scale DRE software • Component middleware • Real-time QoS requirements • Statically: task prioritization, communication bandwidth reservation • Dynamically: runtime reallocation reprioritization for handling bursty CPU load. Reza Eftekhari

  5. Component Middleware • Reusable services, create applications rapidly • CORBA Component Model CCM • Interfaces for collaboration • Component strategies via metadata (XML) • Persistence • Event notification • Transaction • Load balancing • Security Reza Eftekhari

  6. Limitation of DOC • DOC (Distributed Object Computing): • Distributed computing + Object-oriented design • CORBA 2.x (DOC middleware standard) limitations: • Lack of functional boundaries • Lack of generic server standards • Lack of software configuration and deployment standards Reza Eftekhari

  7. Component Middleware addresses DOC limitations • Virtual boundary around app component, well-defined interfaces • Standard container mechanism, generic component servers • Infrastructure to assemble, package, deploy CORBA Component Model CCM Reza Eftekhari

  8. Limitations of Component Middleware for DRE • End-to-end QoS provisioning • Many interacting components • Component server for some resources (thread pools) • Component implementation not right level for QoS provision • Conflicting policies: high throughput, low latency • End-to-end QoS context a priori Solution: Separating programming and QoS concerns • Functional paths: flows of information • QoS systemic paths: end-to-end interaction, failure detection, recovery Reza Eftekhari

  9. Static QoS Provisioning • Fixed set of QoS demand • Tightly bounded predictability for system functionality • Simplest solution available + QoS provisioning integral part of component + Decouple QoS provisioning from component functionality • Aspect-oriented techniques • Crosscut multiple interacting components, end-to-end QoS behavior Reza Eftekhari

  10. Static QoS Provisioning with CIAO • QoS-enable implementation of CCM • Extends TAO (The ACE ORB), support component, end-to-end QoS at system assembly • Application assembly descriptor • QoS-enabled containers • CPU resources: priority models, priority levels • Communication resources: reserving and allocating communication resources, RSVP protocol Usage: • decouple QoS provisioning functionality • Compose static QoS provisioning capabilities into the application via the component assembly and deployment phases Reza Eftekhari

  11. Dynamic QoS Provisioning • Allocation and management of resources at runtime • Events triggers reevaluation and reallocation of resources Dynamic QoS middleware capabilities: • Monitor DRE system, detect changes • Adapt to change, adjust the resource usage Dynamic QoS abstractions and mechanism for DRE systems • Design formalisms: level of service, measured QoS • Runtime capabilities: adapt behavior • Management mechanisms: dynamic control of resources Reza Eftekhari

  12. QuO (Quality Object) Framework Allows DRE developers to specify: • QoS requirements • System elements that must be monitored and controlled to measure and provide QoS • Behavior for adapting to QoS variations that occur at runtime. QuO needs: • Contracts: level of service • Delegates: local proxies for remote components • System Condition objects: interfaces to resources, mechanisms, and ORBs Reza Eftekhari

  13. Conclusion • DRE app QoS: predictability, latency, and dependability • DRE app historically been custom-programmed • expensive to build and maintain, adapt new functional needs • tight coupling between custom DRE software modules • increases the time and effort required to develop • QoS provisioning crosscuts multiple layers in applications • end-to-end enforcement • Component QoS-enable middleware • Static, dynamic provisioning • www.dre.vanderbilt.edu/CIAO • quo.bbn.com Reza Eftekhari

  14. Discussion • End-to-end QoS in IP networks Reza Eftekhari

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