Westwood+ TCP is a sender-side only modification of the classic Tahoe/Reno TCP that has been recently proposed to improve fairness and efficiency of TCP. The key idea of Westwood+ TCP is to perform an end-to-end estimate of the bandwidth available for a TCP connection by properly counting and filtering the stream of ACK packets. This estimate is used to adaptively decrease the congestion window and slow start threshold after a congestion episode. In this way Westwood+ TCP substitutes the classic multiplicative decrease paradigm with the adaptive decrease paradigm. In this paper we report experimental results that have been obtained running Linux 2.2.20 implementations of Westwood+, Westwood and Reno TCP to ftp data over an emulated WAN and over Internet connections spanning continental and intercontinental distances. In particular, collected measurements show that the bandwidth estimation algorithm employed by Westwood+ nicely tracks the available bandwidth, whereas the TCP Westwood bandwidth estimation algorithm greatly overestimates the available bandwidth because of ACK compression. Live Internet measurements also show that Westwood+ TCP improves the goodput w.r.t. TCP Reno. Finally, computer simulations using ns-2 have been developed to test Westwood, Westwood+ and Reno in controlled scenarios. These simulations show that Westwood+ improves fairness and goodput w.r.t. Reno.

Abstract:We propose to extend standard Radio Frequency IDentification (RFID) usage by storing semantically annotated data within RFID tags memory, so that objects may actually 'describe themselves' in a variety of scenarios. In particular here we exploit our approach to carry out an advanced matchmaking process using metadata stored in RFIDs. A 'fully backward compatible' modification to the original RFID data exchange protocol is presented, allowing to implement an advanced resource discovery framework. A compression algorithm specifically devised to ease embedding of annotated DIG description is also proposed. Motivations and benefits of the approach are outlined in a tracking of agricultural and food products case study.Keywords: RFID; Semantic Web; matchmaking; pervasive computing.Reference to this paper should be made as follows: Ruta, M., Di Noia, T., Di Sciascio, E., Scioscia, F. and Piscitelli, G. (2007) Biographical notes: Michele Ruta received the Laurea Degree in Electronic Engineering from Politecnico di Bari (Technical University of Bari) in 2002 and his PhD in InformationEngineering from the same University in 2007. His research interests include pervasive computing and ubiquitous web, mobile service discovery and composition, knowledge representation systems and applications for wireless ad-hoc contexts. On these topics he has co-authored various papers in international journals and conferences. He is involved in various research projects related to his research interests.Tommaso Di Noia is an Assistant Professor in Information Technology Engineering at Technical University of Bari (Politecnico di Bari). He got his PhD from Technical University of Bari. His main scientific interests include: description logics -theoretical and practical aspects; resource matchmaking; knowledge representation systems for electronic commerce; automatic (web) services discovery and composition; knowledge representation systems and applications for the semantic web. He co-authored papers which received the best paper award at conferences ICEC-2004 and IEEE CEC-EEE-2006.

We present an approach to automatic checking of the correctness of web applications structure during their lifecycle. The approach adopts the well-established symbolic model checking technique and the associated tool SMV [13]. A formalism allows the designer to describe the model of a web-based system. Computation Tree Logic (CTL) is adopted as language to define the properties to be verified.The approach has been implemented in a tool to provide automatic support in the design of web applications. The system embeds the NuSMV [1] model checker to perform verification. Verification is carried out after build-ing the finite state model of a site in the model checker input language. To this purpose the system parses the HTML source code of web pages, including code for dynamic pages. Properties are expressed using a user friendly interface for web application developers that automatically translates properties in CTL formulas.

Finding rapidly suitable experts in an organization to compose a team able to solve specific tasks is a typical problem in large consulting firms. In this paper we present a Description Logics approach to the semantic-based composition of ad-hoc teams based on individuals skill profiles and on task description. The selection process is carried out using a novel Concept Covering algorithm that exploits the recently proposed Concept Abduction inference service in Description Logics. The approach has been deployed as part of a skill management system that takes text files with curricula and project specifications as inputs and extracts from them available individual profiles and task descriptions, according to an ontology modeling skills.

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