TagNet: a scalable tag-based information-centric network

The Internet has changed dramatically since the time it was created. What was originally a system to connect relatively few remote users to mainframe computers, has now become a global network of billions of diverse devices, serving a large user population, more and more characterized by wireless communication, user mobility, and large-scale, content-rich, multi-user applications that are stretching the basic end-to-end, point-to-point design of TCP/IP. In recent years, researchers have introduced the concept of Information Centric Networking (ICN). The ambition of ICN is to redesign the Internet with a new service model more suitable to today's applications and users. The main idea of ICN is to address information rather than hosts. This means that a user could access information directly, at the network level, without having to first find out which host to contact to obtain that information. The ICN architectures proposed so far are based on a "pull" communication service. This is because today's Internet carries primarily video traffic that is easy to serve through pull communication primitives. Another common design choice in ICN is to name content, typically with hierarchical names similar to file names or URLs. This choice is once again rooted in the use of URLs to access Web content. However, names offer only a limited expressiveness and may or may not aggregate well at a global scale. In this thesis we present a new ICN architecture called TagNet. TagNet intends to offer a richer communication model and a new addressing scheme that is at the same time more expressive than hierarchical names from the viewpoint of applications, and more effective from the viewpoint of the network for the purpose of routing and forwarding. For the service model, TagNet extends the mainstream "pull" ICN with an efficient "push" network-level primitive. Such push service is important for many applications such as social media, news feeds, and Internet of Things. Push communication could be implemented on top of a pull primitive, but all such implementations would suffer for high traffic overhead and/or poor performance. As for the addressing scheme, TagNet defines and uses different types of addresses for different purposes. Thus TagNet allows applications to describe information by means of sets of tags. Such tag-based descriptors are true content-based addresses, in the sense that they characterize the multi-dimensional nature of information without forcing a partitioning of the information space as is done with hierarchical names. Furthermore, descriptors are completely user-defined, and therefore give more flexibility and expressive power to users and applications, and they also aggregate by subset. By their nature, descriptors have no relation to the network topology and are not intended to identify content univocally. Therefore, TagNet complements descriptors with locators and identifiers. Locators are network-defined addresses that can be used to forward packets between known nodes (as in the current IP network); content identifiers are unique identifiers for particular blocks of content, and therefore can be used for authentication and caching. In this thesis we propose a complete protocol stack for TagNet covering the routing scheme, forwarding algorithm, and congestion control at the transport level. We then evaluate the whole protocol stack showing that (1) the use of both push and pull services at the network level reduces network traffic significantly; (2) the tree-based routing scheme we propose scales well, with routing tables that can store billions of descriptors in a few gigabytes thanks to descriptor aggregation; (3) the forwarding engine with specialized matching algorithms for descriptors and locators achieves wire-speed forwarding rates; and (4) the congestion control is able to effectively and fairly allocate all the bandwidth available in the network while minimizing the download time of an object and avoiding congestion

Synchronization of a WDM Packet-Switched Slotted Ring

In this paper, we present two different strategies of slot synchronization in wavelength-division-multiplexing (WDM) packet-switched slotted-ring networks. Emphasis is given to the architecture behind the WDM Optical Network Demonstrator over Rings (WONDER) project, which is based on tunable transmitters and fixed receivers. The WONDER experimental prototype is currently being developed at the laboratories of Politecnico di Torino. In the former strategy, a slotsynchronization signal is transmitted by the master station on a dedicated control wavelength; in the latter, slave nodes achieve slot synchronization aligning on data packets that are received from the master. The performance of both synchronization strategies, particularly in terms of packet-collision probability, was evaluated by simulation. The technique based on transmitting a timing signal on a dedicated control wavelength achieves better performance, although it is more expensive due to the need for an additional wavelength. However, the technique based on aligning data packets that are received from the master, despite attaining lower timing stability, still deserves further study, particularly if limiting the number of wavelengths and receivers is a major requirement. Some experimental results, which were measured on the WONDER prototype, are also shown. Measurement results, together with theoretical findings, demonstrate the good synchronization performance of the prototype

A system for online beam emittance measurements and proton beam characterization

A system for online measurement of the transverse beam emittance was developed. It is named $^{4}$PrOB$\varepsilon$aM (4-Profiler Online Beam Emittance Measurement) and was conceived to measure the emittance in a fast and efficient way using the multiple beam profiler method. The core of the system is constituted by four consecutive UniBEaM profilers, which are based on silica fibers passing across the beam. The $^{4}$PrOB$\varepsilon$aM system was deployed for characterization studies of the 18~MeV proton beam produced by the IBA Cyclone 18 MeV cyclotron at Bern University Hospital (Inselspital). The machine serves daily radioisotope production and multi-disciplinary research, which is carried out with a specifically conceived Beam Transport Line (BTL). The transverse RMS beam emittance of the cyclotron was measured as a function of several machine parameters, such as the magnetic field, RF peak voltage, and azimuthal angle of the stripper. The beam emittance was also measured using the method based on the quadrupole strength variation. The results obtained with both techniques were compared and a good agreement was found. In order to characterize the longitudinal dynamics, the proton energy distribution was measured. For this purpose, a method was developed based on aluminum absorbers of different thicknesses, a UniBEaM detector, and a Faraday cup. The results were an input for a simulation of the BTL developed in the MAD-X software. This tool allows machine parameters to be tuned online and the beam characteristics to be optimized for specific applications.Comment: published in Journal of Instrumentatio

Software redundancy: what, where, how

Software systems have become pervasive in everyday life and are the core component of many crucial activities. An inadequate level of reliability may determine the commercial failure of a software product. Still, despite the commitment and the rigorous verification processes employed by developers, software is deployed with faults. To increase the reliability of software systems, researchers have investigated the use of various form of redundancy. Informally, a software system is redundant when it performs the same functionality through the execution of different elements. Redundancy has been extensively exploited in many software engineering techniques, for example for fault-tolerance and reliability engineering, and in self-adaptive and self- healing programs. Despite the many uses, though, there is no formalization or study of software redundancy to support a proper and effective design of software. Our intuition is that a systematic and formal investigation of software redundancy will lead to more, and more effective uses of redundancy. This thesis develops this intuition and proposes a set of ways to characterize qualitatively as well as quantitatively redundancy. We first formalize the intuitive notion of redundancy whereby two code fragments are considered redundant when they perform the same functionality through different executions. On the basis of this abstract and general notion, we then develop a practical method to obtain a measure of software redundancy. We prove the effectiveness of our measure by showing that it distinguishes between shallow differences, where apparently different code fragments reduce to the same underlying code, and deep code differences, where the algorithmic nature of the computations differs. We also demonstrate that our measure is useful for developers, since it is a good predictor of the effectiveness of techniques that exploit redundancy. Besides formalizing the notion of redundancy, we investigate the pervasiveness of redundancy intrinsically found in modern software systems. Intrinsic redundancy is a form of redundancy that occurs as a by-product of modern design and development practices. We have observed that intrinsic redundancy is indeed present in software systems, and that it can be successfully exploited for good purposes. This thesis proposes a technique to automatically identify equivalent method sequences in software systems to help developers assess the presence of intrinsic redundancy. We demonstrate the effectiveness of the technique by showing that it identifies the majority of equivalent method sequences in a system with good precision and performance

Healing Web applications through automatic workarounds

We develop the notion of automatic workaround in the context of Web applications. A workaround is a sequence of operations, applied to a failing component, that is equivalent to the failing sequence in terms of its intended effect, but that does not result in a failure. We argue that workarounds exist in modular systems because components often offer redundant interfaces and implementations, which in turn admit several equivalent sequences of operations. In this paper, we focus on Web applications because these are good and relevant examples of component-based (or service-oriented) applications. Web applications also have attractive technical properties that make them particularly amenable to the deployment of automatic workarounds. We propose an architecture where a self-healing proxy applies automatic workarounds to a Web application server. We also propose a method to generate equivalent sequences and to represent and select them at run-time as automatic workarounds. We validate the proposed architecture in four case studies in which we deploy automatic workarounds to handle four known failures in to the popular Flickr and Google Maps Web application

Regulation and functions of bacterial PNPase

Polynucleotide phosphorylase (PNPase) is an exoribonuclease that catalyzes the processive phosphorolytic degradation of RNA from the 3\u2032-end. The enzyme catalyzes also the reverse reaction of polymerization of nucleoside diphosphates that has been implicated in the generation of heteropolymeric tails at the RNA 3\u2032-end. The enzyme is widely conserved and plays a major role in RNA decay in both Gram-negative and Gram-positive bacteria. Moreover, it participates in maturation and quality control of stable RNA. PNPase autoregulates its own expression at post-transcriptional level through a complex mechanism that involves the endoribonuclease RNase III and translation control. The activity of PNPase is modulated in an intricate and still unclear manner by interactions with small molecules and recruitment in different multiprotein complexes. Not surprisingly, given the wide spectrum of PNPase substrates, PNPase-defective mutations in different bacterial species have pleiotropic effects and perturb the execution of genetic programs involving drastic changes in global gene expression such as biofilm formation, growth at suboptimal temperatures, and virulence

MISURAZIONE DIRETTA DEL TRAFFICO NERVOSO SIMPATICO IN DIFFERENTI FASI DELL'ACROMEGALIA

Sympathovagal imbalance has been shown in acromegaly by indirect measurements of adrenergic tone. Data regarding direct measurement of sympathetic activity are lacking as yet. Aim of this study was to assess the adrenergic tone through direct recording of muscle sympathetic nerve activity (MSNA) in acromegalic patients. Skin sympathetic nerve traffic (SSNA) was also recordered. Study: After evaluating anthropometric and echocardiographic parameters, anterior pituitary function, glucose and lipid metabolism, and measuring plasma leptin, direct recording of sympathetic outflow via the microneurographic technique was performed in the following groups of subjects: 15 newly diagnosed acromegalics without hyperprolactinaemia, pituitary hormone deficiencies, obstructive sleep apnoea and cardiac hypertrophy (GROUP 1); 22 patients on somatostatin analogues (SSA), 11 of whom attaining biochemical control according to the currently accepted criteria and 11 not attaining biochemical control (GROUP 3); 2 acromegalic patients affected by OSAS (GROUP 4); 10 patients cured from acromegaly after neurosurgery (GROUP 5). The 15 newly diagnosed acromegalic patients were also studied for SSNA (GROUP 2). Fiften normalweight healthy subjects serving as controls. Results For similar anthropometric and metabolic parameters in patients and contros the group 1 displayed insulin resistance and a marked sympathetic inhibition (MSNA 18\u20223 \ub1 8\u202210) vs controls (37\u20223 \ub1 6\u202248 bursts/ min). A significant reduction in plasma leptin (1\u20226 \ub1 1\u202204 vs 6\u20225 \ub1 2\u202201 lg/l, P < 0\u20220001) was also recorded in patients. Patients on SSA (GROUP 3), either with controlled or uncontrolled disease, displayed mean MSNA values (27.4 \ub1 8.24 and 31.6 \ub1 3.27 bursts/min, respectively) significantly lower than those shown by controls (p < 0.01) but significantly higher than those found in untreated acromegalics (p < 0.05). Mean MSNA values were not significantly different between controlled and uncontrolled SSA-treated patients. GROUP 5 showed mean MSNA values (30.17 \ub1 3.2 bursts/min) significantly higher than those shown by GROUP 1 (p< 0.01) and than patients non controlled by SSA (p<0.05), but superimposable to that of patients controlled by SSA and controls. Mean leptin levels of cured were significantly higher than those shown by active patients (p<0.01). MSNA levels registered in two patients affected by OSAS (GROUP 4) was higher than those found in acromegalic patients without OSAS. There were no significant differences in SSNA between GROUP 2 and controls. Considering the whole population IGF-1 levels were negative correlated with MSNA and leptin levels ( p<0.05 and p<0.0005, respectively) and MSNA was positive correlated with leptin levels (p<0.05). Comment. Our study demonstrates that recently diagnosed acromegalic patients, in spite of insulin resistance (a condition known to increase MSNA), display a decreased sympathetic outflow. This finding, together with the tendency to normalization of adrenergic tone in pharmacologically treated and cured acromegalic patients and the negative correlations found between IGF-1 on the one hand and leptin and MSNA on the other hand, and the positive correlation between leptin and MSNA, suggests a relevant influence of the GH/IGF-I axis on the activity of the sympathetic nervous system through leptin modification