Although Web services are generally envisioned as being stateless, some of them are implicitly stateful. The reason is that the Web services often work as front-ends to enterprise systems and are used in a session-ori...
详细信息
Although Web services are generally envisioned as being stateless, some of them are implicitly stateful. The reason is that the Web services often work as front-ends to enterprise systems and are used in a session-oriented way by the clients. Contrary to the case of stateless services, for a stateful Web service there exist constraints to the order in which the operations of the service may be invoked. However, specification of such constraints is not a standard part of a Web service interface, and compliance with such constraints is not checked by the standard Web service development tools. Therefore, we propose in this paper to extend a web service interface by a constraint definition that is based on behavior protocols. Also, we implemented a tool that checks whether a given BPEL code complies with the constraints of all stateful web services it communicates with. The key idea behind the tool is to translate the BPEL code into Java and then to check the Java program using Java PathFinder with behavior protocol extension.
The design of optical transport and IP networks is investigated with respect to the effect on overall network performance when the two aspects are combined in the same network architecture. The focus is on the identif...
详细信息
ISBN:
(纸本)9783800730971
The design of optical transport and IP networks is investigated with respect to the effect on overall network performance when the two aspects are combined in the same network architecture. The focus is on the identification of advantages in the joint design of IP and transport networks, as well as on the shortcomings and network bottlenecks which may result from sub-optimal design. The impact of different IP routing strategies (shortest path, equal-cost multipath) on the network utilization is quantified, and potential sources for overload in the IP domain are determined. Simulations were carried out to systematically assess technical metrics like link utilization and economic parameters such as cost for a 50-node transport network with line rates up to 40 Gbit/s. The impact of fiber cuts was taken into account, leading to multiple logical IP links to fail simultaneously, i.e. shared risk link groups (SRLGs), and triggering massive IP rerouting. Applying the results allows to identify bottlenecks in the design, and to devise mechanisms which allow cost-optimal network design of future IP and optical transport networks.
Television over the Internet (IPTV) is regarded as the killer application for Next Generation Networks (NGN). While the ITU is currently moving toward the standardized of IPTV, several existing applications like Joost...
详细信息
Television over the Internet (IPTV) is regarded as the killer application for Next Generation Networks (NGN). While the ITU is currently moving toward the standardized of IPTV, several existing applications like Joost and Zattoo are currently already providing a large amount of video content to Internet users. In this paper we study some popular video content delivery mechanisms and characterize them by measurements to study the user-perceived Quality of Experience (QoE).
The development of web services and especially semantic web services is a tremendous task for people who are not familiar with all language constructs. Especially with the growing mass of several semantic web service ...
详细信息
ISBN:
(纸本)9789898111005
The development of web services and especially semantic web services is a tremendous task for people who are not familiar with all language constructs. Especially with the growing mass of several semantic web service approaches a language-independent service development is needed. This gap can be filled by using model-driven software development. Therefore, in this paper we introduce a meta-model for semantic web services and show the benefits of automatic code generation on the basis of a small example.
Data management is a key aspect of any distributed system. This paper surveys data management techniques in various distributedsystems, starting from distributed Shared Memory (DSM) systems to Peer-to-Peer (P2P) syst...
详细信息
This tutorial presents the definition, the models and the techniques of location privacy from the data privacy perspective. By reviewing and revising the state of art research in data privacy area, the presenter descr...
详细信息
ISBN:
(纸本)9781595936493
This tutorial presents the definition, the models and the techniques of location privacy from the data privacy perspective. By reviewing and revising the state of art research in data privacy area, the presenter describes the essential concepts, the alternative models, and the suite of techniques for providing location privacy in mobile and ubiquitous data management systems. The tutorial consists of two main components. First, we will introduce location privacy threats and give an overview of the state of art research in data privacy and analyze the applicability of the existing data privacy techniques to location privacy problems. Second, we will present the various location privacy models and techniques effective in either the privacy policy based framework or the location anonymization based framework. The discussion will address a number of important issues in both data privacy and location privacy research, including the location utility and location privacy trade-offs, the need for a careful combination of policy-based location privacy mechanisms and location anonymization based privacy schemes, as well as the set of safeguards for secure transmission, use and storage of location information, reducing the risks of unauthorized disclosure of location information. The tutorial is designed to be self-contained, and gives the essential background for anyone interested in learning about the concept and models of location privacy, and the principles and techniques for design and development of a secure and customizable architecture for privacy-preserving mobile data management in mobile and pervasive information systems. This tutorial is accessible to data management administrators, mobile location based service developers, and graduate students and researchers who are interested in data management in mobile information syhhhstems, pervasive computing, and data privacy. Copyright 2007 VLDB Endowment, ACM.
Applications like weather forecasting and prediction, health-care monitoring, habitat monitoring, tsunami-warning systems, demand integration of Wireless Sensor Networks (WSNs) with grids. The issues that need to be a...
详细信息
Restoration or protection switching mechanisms are triggered by link or node failures to redirect traffic over backup paths. These paths then carry the normal and the backup traffic which may lead to overload and ther...
详细信息
ISBN:
(纸本)3540699619
Restoration or protection switching mechanisms are triggered by link or node failures to redirect traffic over backup paths. These paths then carry the normal and the backup traffic which may lead to overload and thereby to quality of service (QoS) violations, i.e. to excessive packet loss and delay. In this paper, we present a method to assess the potential overload of the links due to network failures. We calculate the complementary cumulative distribution function (CCDF) of the relative load for each link in the network. We discuss various performance measures that condense this information to a single value per link which is suitable for a link ranking. This helps to identify weak spots of the network and to appropriately upgrade the bandwidth of links although they are not overloaded during normal operation. We implemented the concept in a software tool which helps network providers to anticipate the potential overload in their networks prior to failures and intended modifications (new infrastructure, new routing, new customers,) and to take appropriate actions.
In this paper, we evaluate the performance of a P2P- based content distribution system in heterogeneous, wireless networks. The mobile users coordinate each other with cooperation strategies enabled by the multi-sourc...
详细信息
In this paper, we evaluate the performance of a P2P- based content distribution system in heterogeneous, wireless networks. The mobile users coordinate each other with cooperation strategies enabled by the multi-source download mechanism, as in eDonkey or BitTorrent. Due to the mobility, vertical handovers between different wireless access technologies are required which may result in transmission delays and IP address changes of the switching peer. Hence, connections among users have to be reestablished and downloading users are requeued at a providing peer's waiting queue. In detail, we investigate the impact of requeueing with each VHO as well as the use of mechanisms that preserve the IP address and connections beyond VHOs, like MobilelP. Another important phenomenon occurring with VHOs is the abrupt change of the available bandwidth, e.g., from a fast WLAN connection to a rather slow UMTS connection. We evaluate the download times for files by means of simulation while considering different load scenarios in today's and future network layouts of the B3G network. As a result of the performance evaluation, we derive a new time-based cooperation strategy that counters the impact of mobility. Instead of downloading individual blocks of a file, a user gets a time slot at a providing peer. We show that this leads to a significant performance gain.
In UMTS networks, HSDPA users share radio resources like transmit power and OSVF codes with QoS-users, which use dedicated channels as primary transport method. Several options for the resource allocation for HSDPA ex...
详细信息
In UMTS networks, HSDPA users share radio resources like transmit power and OSVF codes with QoS-users, which use dedicated channels as primary transport method. Several options for the resource allocation for HSDPA exist, which center around the question whether resources should be exclusively reserved for HSDPA, or whether the resources for the HSDPA should be adapted to the requirements of the QoS users. We investigate the impact of three radio resource allocation schemes on the HSDPA and on the dedicated channel performance by means of a time-dynamic simulation. The numerical results show the trade-offs between dedicated channel and HSDPA performance and the sensitivity of the system against power and code reservation parameters.
暂无评论