Using XML-Based Multicasting to Improve Web Service Scalability

Abstract

Web services’ (WS) emphasis on open standards provides substantial benefits over previous application integration techniques. A major WS feature is SOAP, a simple, robust and extensible XML-based protocol for the exchange of messages. For this reason, SOAP WS on virtual hosts are now widely used to provide shared functionalities on clouds. Unfortunately, SOAP has two major performance-related drawbacks: i) verbosity, related to XML, that leads to increased network traffic, and ii) high computational burden of XML parsing and processing, that leads to high latency. In this paper, we address these two issues and present new results regarding our framework for Differential SOAP Multicasting (DSM). The main idea behind our framework is identifying the common pattern and differences between SOAP messages, modeled as trees, so as to multicast similar messages together. Our method is based on the well known concept of Tree Edit Distance, built upon a novel filter-differencing architecture to reduce message aggregation time, identifying only those messages which are relevant (i.e., similar enough) for similarity evaluation. In this paper we focus on recent improvements to the filter-differencing architecture, including a dedicated differencing output format designed to carry the minimum amount of diff information, in the multicast message, so as to minimize the multicast message size, and therefore reduce the network traffic. Simulation experiments highlight the relevance of our method in comparison with traditional and dedicated multicasting techniques.