Wirelessly networked dynamic and mobile environments, such as tactical military environments, pose many challenges to building distributed computing systems. A wide variety of node types and resources, unreliable and bandwidth constrained communications links, high chum rates, and rapidly changing user demands and requirements make it difficult to build systems that satisfy the needs of the users and provide good performance. Agile c ._mputing is an innovative metaphor for distributed computing systems and prescribes a new approach to their design and implementation. Agile computing may be defined as opportunistically discovering, manipulating, and exploiting available computing and communication resources. The term agile is used to highlight the desire to both quickly react to changes in the environment as well as to take advantage of transient resources only available for short periods of time. This thesis describes the overall agile computing metaphor as well as one concrete realisation through a middleware infrastructure. An important contribution of the thesis is the definition of a generic architecture for agile computing, which identifies the core and ancillary attributes that contribute to systems that are to be agile. The thesis also describes the design and implementation of one concrete middleware solution, which provides a number of components and capabilities that integrate together to address the challenges of the overall problem. These components include the Aroma virtual machine, the Mockets communications library, the Group Manager resource discovery component, the DisService peer-to-peer information dissemination system, and the AgServe service oriented architecture. The design and development of these components has been motivated by observing problems with real systems in tactical military environments. As a result, the components have been incorporated into real systems and used in the field. The key contribution of this thesis is the prescribed approach to combining these capabilities in order to build opportunistic systems. The capabilities of these components, both individually, as well as part of a single integrated system, are evaluated through a series of experiments and compared with existing systems and standards. The results show significant performance improvements for each of the components. For example, the Mockets library performs up to 7.6x better than TCP (Transmission Control Protocol) sockets in terms of throughput depending on the type of radio utilised. When exploiting unique features in the Mockets library, such as message replacement, the Mockets library performs up to 44x better than SCTP (Stream Control Transmission Protocol) and SCPS (Space Communications Protocol Standards) in terms of timeliness of delivery of data. Likewise, when compared to the JXTA middleware from Sun Microsystems, the Group Manager uses up to 4.8x less bandwidth to support service discovery. Finally, experiments to measure the agility of the integrated middleware show that transient resources that are available for as short a period as 10 seconds can be opportunistically exploited. The Agile Computing Middleware, as presented in this thesis, continues to evolve in terms of further optimisations, incorporation of new components, enhancement of the existing components, and test and evaluation in real-world demonstrations and exercises. It is also hoped that the definition of the concept of agile computing and a general architecture for agile computing will encourage other researchers to build new systems that adopt and advance the notions of agile computing.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:533102 |
| Date | January 2008 |
| Creators | Suri, Niranjan |
| Publisher | Lancaster University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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