WebPADS : a Web proxy for actively deployable services

viii, 139 leaves : ill. ; 30 cm.PolyU Library Call No.: [THS] LG51 .H577M COMP 2002 ChuangThe success of wireless cellular technology has led to the evolution of a highly mobile computing model that is based on the potentially unconstrained movement of clients using wireless connectivity. However, the wireless environment is drastically different from its wired counterpart. Many design assumptions, upon which existing protocols and applications for fixed network environment are built, are no longer appropriate in a wireless environment. In particular, bandwidth, latency, and error rates are all significantly poorer, and varying and asymmetric in nature, which leads to sub-optimal utilization of a wireless link when it is used by Web applications. Several new services and extensions have been proposed to overcome these problems. However, these solutions are static since the services require a priori installation and configuration of the Web server or the Web proxy. This means that a mobile node is not able to benefit from new or dynamic services as it moves to a foreign network that does not provide the specified services. Consequently, the capabilities of these existing solutions are limited by this deployment problem. It is desirable to support a dynamic architecture for Web traffic, so that new services can be introduced and configured in a continuously changing wireless environment. A mobile node would then be able to dynamically deploy any appropriate services that it needs onto the foreign network, based on the conditions and characteristics of the wireless link. The focus of this thesis is on alleviating the shortcomings of the existing proposals. We propose an active service deployment model where the proxy is composed of a chain of service objects called mobilets (pronounced as mo-be-lets), which can be deployed onto the network actively. This model offers flexibility because the chain of mobilets can be dynamically reconfigured to adapt to the vigorous changes in the characteristics of a wireless environment, without interrupting the service provision for other mobile nodes. Furthermore, mobilets can also be migrated to a new proxy server when the mobile node moves to a different network domain. We have realized the active service deployment model by crafting its design into a programmable infrastructure that forms the baseline architecture of the WebPADS (short for Web Proxy for Actively Deployable Services) system.Department of ComputingM.Phil., Dept. of Computing, The Hong Kong Polytechnic University, 2002