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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Cognizant Networks: A Model and Framework for Session-based Communications and Adaptive Networking

Kalim, Umar 09 August 2017 (has links)
The Internet has made tremendous progress since its inception. The kingpin has been the transmission control protocol (TCP), which supports a large fraction of communication. With the Internet's wide-spread access, users now have increased expectations. The demands have evolved to an extent which TCP was never designed to support. Since network stacks do not provide the necessary functionality for modern applications, developers are forced to implement them over and over again --- as part of the application or supporting libraries. Consequently, application developers not only bear the burden of developing application features but are also responsible for building networking libraries to support sophisticated scenarios. This leads to considerable duplication of effort. The challenge for TCP in supporting modern use cases is mostly due to limiting assumptions, simplistic communication abstractions, and (once expedient) implementation shortcuts. To further add to the complexity, the limited TCP options space is insufficient to support extensibility and thus, contemporary communication patterns. Some argue that radical changes are required to extend the networks functionality; some researchers believe that a clean slate approach is the only path forward. Others suggest that evolution of the network stack is necessary to ensure wider adoption --- by avoiding a flag day. In either case, we see that the proposed solutions have not been adopted by the community at large. This is perhaps because the cost of transition from the incumbent to the new technology outweighs the value offered. In some cases, the limited scope of the proposed solutions limit their value. In other cases, the lack of backward compatibility or significant porting effort precludes incremental adoption altogether. In this dissertation, we focus on the development of a communication model that explicitly acknowledges the context of the conversation and describes (much of) modern communications. We highlight how the communication stack should be able to discover, interact with and use available resources to compose richer communication constructs. The model is able to do so by using session, flow and endpoint abstractions to describe communications between two or more endpoints. These abstractions provide means to the application developers for setting up and manipulating constructs, while the ability to recognize change in the operating context and reconfigure the constructs allows applications to adapt to the changing requirements. The model considers two or more participants to be involved in the conversation and thus enables most modern communication patterns, which is in contrast with the well-established two-participant model. Our contributions also include an implementation of a framework that realizes such communication methods and enables future innovation. We substantiate our claims by demonstrating case studies where we use the proposed abstractions to highlight the gains. We also show how the proposed model may be implemented in a backwards compatible manner, such that it does not break legacy applications, network stacks, or middleboxes in the network infrastructure. We also present use cases to substantiate our claims about backwards compatibility. This establishes that incremental evolution is possible. We highlight the benefits of context awareness in setting up complex communication constructs by presenting use cases and their evaluation. Finally, we show how the communication model may open the door for new and richer communication patterns. / PHD / In this dissertation, we focus on the development of a communication model that explicitly acknowledges the context of the conversation and describes (much of) modern communications. We highlight how the networking software should be able to discover, interact with and use available resources. The model is able to do so by using abstractions that describe communications between participants as if human beings were having a conversation i.e., the semantics of interactions between participants are defined in terms of a conversation session. These abstractions provide means to the application developers for describing communications in a holistic manner, recognizing change in the context and reconfigure communications to allow adaptation to changing requirements. The model considers two or more participants to be involved in the conversation and thus enables most modern communication patterns, which is in contrast with the well-established two-participant legacy model. Our contributions also include an implementation of a framework that realizes such communication methods and enables future innovation. We substantiate our claims by demonstrating case studies where we use the proposed abstractions to highlight the gains. We also show how the proposed model may be implemented in a backwards compatible manner, such that it does not break legacy applications, networking software, or network infrastructure. We also present use cases to substantiate our claims about backwards compatibility. This establishes that incremental evolution is possible. We highlight the benefits of context awareness in setting up complex communication constructs by presenting use cases and their evaluation. Finally, we show how the communication model may open the door for new and richer communication patterns.
2

Determination of Real-Time Network Configuration for Self-Adaptive Automotive Systems

Zhang, Ziming 19 May 2015 (has links) (PDF)
The Electric/Electronic architecture of vehicle becomes more complex and costly, self-adaption can reduce the system, enhance the adaptive meanwhile reduce energy consumption and costs. The self-adaption needs the cooperation of both hardware and software reconfigurations, such that after the software is reconfigured the automotive network continues to fulfill the time constraints for time-critical applications. The thesis focuses on the real-time network reconfiguration. It uses EAST-ADL to model a real-time automotive system with timing events and constraints, which conforms to AUTOSAR timing extensions. The network media access is analyzed based on the model and a scheduling algorithm is developed. Then the concept is implemented by a use case, which is transformed from an EAST-ADL model to an executable simulation.
3

Determination of Real-Time Network Configuration for Self-Adaptive Automotive Systems

Zhang, Ziming 17 April 2015 (has links)
The Electric/Electronic architecture of vehicle becomes more complex and costly, self-adaption can reduce the system, enhance the adaptive meanwhile reduce energy consumption and costs. The self-adaption needs the cooperation of both hardware and software reconfigurations, such that after the software is reconfigured the automotive network continues to fulfill the time constraints for time-critical applications. The thesis focuses on the real-time network reconfiguration. It uses EAST-ADL to model a real-time automotive system with timing events and constraints, which conforms to AUTOSAR timing extensions. The network media access is analyzed based on the model and a scheduling algorithm is developed. Then the concept is implemented by a use case, which is transformed from an EAST-ADL model to an executable simulation.:1. Introduction 2. Research Fundamentals 2.1. AUTOSAR Specifications for Modeling Function Communication 2.2. Media Access Control in Real-time Network 3. Function Communication Model and Determination of Network Configuration 3.1. Function Communication Model 3.2. Scheduling Algorithm for Media Access 4. Implementation of Communication Model and Plugin for Model Transformation 4.1. EAST-ADL Modeling Language 4.2. Implementation of Function Communication Model in EAST-ADL 4.3. Model Transformation Plugin and Simulation Tool Integration 5. Evaluation of the Function Communication Model 5.1. Use-Case Model for Evaluation 5.2. Time Values of Use-Case Model 5.3. Analysis and Evaluation of Simulation Result 6. Conclusion and Outlook 6.1. Conclusion of the Work 6.2. Outlook of the Future Work A. OMNeT++ Simulation Log B. EAST-ADL Model to Artop Model Mapping Bibliography Nomenclature

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