Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P12

The explosive growth of distributed computing has been fuelled by many factors. Applications such as video conferencing, teleoperation and most notably the World Wide Web are placing ever more demanding requirements on their underlying communication systems. Having never been designed to support such diverse communication patterns these systems are failing to provide appropriate services to individual applications. Artificial neural networks have been used in areas of communication systems including signal processing and call management (Kartalopolus, 1994)....
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P12 Telecommunications Optimization: Heuristic and Adaptive Techniques. Edited by David W. Corne, Martin J. Oates, George D. Smith Copyright © 2000 John Wiley & Sons Ltd ISBNs: 0-471-98855-3 (Hardback); 0-470-84163X (Electronic)12Neural Networks for theOptimization of RuntimeAdaptable CommunicationProtocolsRobert S. Fish and Roger J. Loader12.1 IntroductionThe explosive growth of distributed computing has been fuelled by many factors.Applications such as video conferencing, teleoperation and most notably the World WideWeb are placing ever more demanding requirements on their underlying communicationsystems. Having never been designed to support such diverse communication patterns thesesystems are failing to provide appropriate services to individual applications. Artificial neural networks have been used in areas of communication systems includingsignal processing and call management (Kartalopolus, 1994). This chapter suggests a furtheruse of neural networks for the maintenance of application tailored communication systems.In this context, a neural network minimises the difference between an applications requiredQuality of Service (QoS) and that provided by the end-to-end connection.12.1.1 Problem areaCommunication systems based on the ISO Open System Interconnection (OSI) modelhistorically suffered inefficiencies such as function duplication and excessive data copying.Telecommunications Optimization: Heuristic and Adaptive Techniques, edited by D. Corne, M.J. Oates and G.D. Smith© 2000 John Wiley & Sons, Ltd200 Telecommunications Optimization: Heuristic and Adaptive TechniquesHowever, a combination of modern protocol implementation techniques and an increase inthe power and resources of modern computers has largely eliminated these overheads.Zitterbart (1993) defines the characteristics of various distributed applications and identifesfour possible classes based on their communication requirements. Table 12.1 illustratesthese classifications and highlights the broad range of transport services required by moderndistributed applications. In the face of such diversity, the challenge of optimizingperformance shifts from the efficiency of individual mechanisms to the provision of aservice that best satisfies the broad range of application requirements. Providing such aservice is further complicated by external factors such as end-to-end connectioncharacteristics, host heterogeneity and fluctuations in network utilization. Traditionalprotocols, such as TCP/IP do not contain the broad functionality necessary to satisfy allapplication requirements in every operating environment. In addition, the QoS required byan application may change over the lifetime of a connection. If a protocol provides a greaterQoS than is required then processor time and network bandwidth may be wasted. For thesereasons, applications that use existing protocols do not necessarily receive thecommunication services they require. Table 12.1 Diversity of application transport requirements.Transport service Example Average Burst Delay Jitter Order Loss Priorityclass applications throughput Factor sens. sens. sens. Tol. DeliveryInteractive Voice Low Low High High Low High NoTime Critical Tele conf Mod Mod High High Low Mod Yes Motion videoDistributed Compressed High High High Mod Low Mod YesTime Critical Motion video raw Very high Low High High Low Mod YesReal Time ManufactureTime Critical Control Mod Mod High Var High Low YesNon Real File transfer Mod Low Low N/D High None NoTime TELNET Very low High High Low High None YesNon Time Trans. process Low High High Low Var None NoCritical File service Low High High Low Var None No Configurable protocols offer customised communication services that are tailored to aparticular set of application requirements and end-to-end connection characteristics. Theymay be generated manually, through formal languages or graphical tools, or automaticallywith code scanning parsers that determine application communication patterns.12.1.2 Adaptable Communication SystemsWhilst configurable communication systems provide ...