A Service Query Dissemination Algorithm for Accommodating Sophisticated QoS Requirements in a Service Discovery System
For many service discovery protocols, user service queries need to be disseminated to some service directories within the system for discovering matched services. The scope of dissemination identifies the scope of service discovery. How to determine the s
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Abstract. For many service discovery protocols, user service queries need to be disseminated to some service directories within the system for discovering matched services. The scope of dissemination identifies the scope of service discovery. How to determine the service discovery scope needs to be discussed. In this paper, we present a service query dissemination algorithm in our developing service discovery system, Service CatalogNet. In this system, users can pose different QoS requirements upon their service queries in order to manually control the scope of service discovery. The service query dissemination algorithm will dynamically transform the QoS requirements into a set of directories as well as the routing paths to them. The performance analysis shows a sound result of our algorithm. Keywords: QoS, multicast, service discovery, mobile computing, NPcomplete.
1 Introduction Recent trends in mobile and ubiquitous computing have created new requirements for automatic configuration of network devices. Furthermore, the exploding deployment of network devices in diverse environment has increased the need to simplify the network administration for different kinds of networks. In response to these requirements, a variety of new protocols have been proposed, which attempt to provide automatic discovery and configuration of network devices and services. These protocols are called service discovery protocols [1]. The majority service discovery protocols rely on a special component called service directory, or directory in short, for maintaining service information. Users post service queries to a directory for services they need. To enhance scalability and robustness, the whole set of service information within a system is normally distributed to a set of directories across the system. In this circumstance, user service queries are first sent to a specific directory called access directory and then dynamically forwarded to a set of other directories for service discovery. The challenge is how to select an appropriate subset of directories within the system as well as the routing paths to them. Within the entire spectrum of directory selection, there are two extreme T.-W. Kuo et al. (Eds.): EUC 2007, LNCS 4808, pp. 577–586, 2007. © IFIP International Federation for Information Processing 2007
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L. Zhang and B. Jin
strategies: full-directory strategy, where the user desires the service query to be processed at all the directories within the system, and no-directory strategy, where the system restricts the service query only at the access directory for minimizing the transmission cost. Both the user requirement of maximizing the processing directories and the system requirement of minimizing the transmission cost are referred to as QoS requirements. Our problem can be defined as dynamically determining the directories and routing paths for disseminating service queries with the consideration of an ordered list of user and system QoS requirements according to the priority. For example, a service query will be diss
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