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Search Results: 1 - 10 of 42 matches for " Udi Weinsberg "
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Topological Trends of Internet Content Providers
Yuval Shavitt,Udi Weinsberg
Computer Science , 2012,
Abstract: The Internet is constantly changing, and its hierarchy was recently shown to become flatter. Recent studies of inter-domain traffic showed that large content providers drive this change by bypassing tier-1 networks and reaching closer to their users, enabling them to save transit costs and reduce reliance of transit networks as new services are being deployed, and traffic shaping is becoming increasingly popular. In this paper we take a first look at the evolving connectivity of large content provider networks, from a topological point of view of the autonomous systems (AS) graph. We perform a 5-year longitudinal study of the topological trends of large content providers, by analyzing several large content providers and comparing these trends to those observed for large tier-1 networks. We study trends in the connectivity of the networks, neighbor diversity and geographical spread, their hierarchy, the adoption of IXPs as a convenient method for peering, and their centrality. Our observations indicate that content providers gradually increase and diversify their connectivity, enabling them to improve their centrality in the graph, and as a result, tier-1 networks lose dominance over time.
Near-Deterministic Inference of AS Relationships
Yuval Shavitt,Eran Shir,Udi Weinsberg
Computer Science , 2007,
Abstract: The discovery of Autonomous Systems (ASes) interconnections and the inference of their commercial Type-of-Relationships (ToR) has been extensively studied during the last few years. The main motivation is to accurately calculate AS-level paths and to provide better topological view of the Internet. An inherent problem in current algorithms is their extensive use of heuristics. Such heuristics incur unbounded errors which are spread over all inferred relationships. We propose a near-deterministic algorithm for solving the ToR inference problem. Our algorithm uses as input the Internet core, which is a dense sub-graph of top-level ASes. We test several methods for creating such a core and demonstrate the robustness of the algorithm to the core's size and density, the inference period, and errors in the core. We evaluate our algorithm using AS-level paths collected from RouteViews BGP paths and DIMES traceroute measurements. Our proposed algorithm deterministically infers over 95% of the approximately 58,000 AS topology links. The inference becomes stable when using a week worth of data and as little as 20 ASes in the core. The algorithm infers 2-3 times more peer-to-peer relationships in edges discovered only by DIMES than in RouteViews edges, validating the DIMES promise to discover periphery AS edges.
Recommending with an Agenda: Active Learning of Private Attributes using Matrix Factorization
Smriti Bhagat,Udi Weinsberg,Stratis Ioannidis,Nina Taft
Computer Science , 2013,
Abstract: Recommender systems leverage user demographic information, such as age, gender, etc., to personalize recommendations and better place their targeted ads. Oftentimes, users do not volunteer this information due to privacy concerns, or due to a lack of initiative in filling out their online profiles. We illustrate a new threat in which a recommender learns private attributes of users who do not voluntarily disclose them. We design both passive and active attacks that solicit ratings for strategically selected items, and could thus be used by a recommender system to pursue this hidden agenda. Our methods are based on a novel usage of Bayesian matrix factorization in an active learning setting. Evaluations on multiple datasets illustrate that such attacks are indeed feasible and use significantly fewer rated items than static inference methods. Importantly, they succeed without sacrificing the quality of recommendations to users.
The Shapley Value in Knapsack Budgeted Games
Smriti Bhagat,Anthony Kim,S. Muthukrishnan,Udi Weinsberg
Computer Science , 2014,
Abstract: We propose the study of computing the Shapley value for a new class of cooperative games that we call budgeted games, and investigate in particular knapsack budgeted games, a version modeled after the classical knapsack problem. In these games, the "value" of a set $S$ of agents is determined only by a critical subset $T\subseteq S$ of the agents and not the entirety of $S$ due to a budget constraint that limits how large $T$ can be. We show that the Shapley value can be computed in time faster than by the na\"ive exponential time algorithm when there are sufficiently many agents, and also provide an algorithm that approximates the Shapley value within an additive error. For a related budgeted game associated with a greedy heuristic, we show that the Shapley value can be computed in pseudo-polynomial time. Furthermore, we generalize our proof techniques and propose what we term algorithmic representation framework that captures a broad class of cooperative games with the property of efficient computation of the Shapley value. The main idea is that the problem of determining the efficient computation can be reduced to that of finding an alternative representation of the games and an associated algorithm for computing the underlying value function with small time and space complexities in the representation size.
CARE: Content Aware Redundancy Elimination for Disaster Communications on Damaged Networks
Udi Weinsberg,Athula Balachandran,Nina Taft,Gianluca Iannaccone,Vyas Sekar,Srinivasan Seshan
Computer Science , 2012,
Abstract: During a disaster scenario, situational awareness information, such as location, physical status and images of the surrounding area, is essential for minimizing loss of life, injury, and property damage. Today's handhelds make it easy for people to gather data from within the disaster area in many formats, including text, images and video. Studies show that the extreme anxiety induced by disasters causes humans to create a substantial amount of repetitive and redundant content. Transporting this content outside the disaster zone can be problematic when the network infrastructure is disrupted by the disaster. This paper presents the design of a novel architecture called CARE (Content-Aware Redundancy Elimination) for better utilizing network resources in disaster-affected regions. Motivated by measurement-driven insights on redundancy patterns found in real-world disaster area photos, we demonstrate that CARE can detect the semantic similarity between photos in the networking layer, thus reducing redundant transfers and improving buffer utilization. Using DTN simulations, we explore the boundaries of the usefulness of deploying CARE on a damaged network, and show that CARE can reduce packet delivery times and drops, and enables 20-40% more unique information to reach the rescue teams outside the disaster area than when CARE is not deployed.
Privacy Tradeoffs in Predictive Analytics
Stratis Ioannidis,Andrea Montanari,Udi Weinsberg,Smriti Bhagat,Nadia Fawaz,Nina Taft
Computer Science , 2014,
Abstract: Online services routinely mine user data to predict user preferences, make recommendations, and place targeted ads. Recent research has demonstrated that several private user attributes (such as political affiliation, sexual orientation, and gender) can be inferred from such data. Can a privacy-conscious user benefit from personalization while simultaneously protecting her private attributes? We study this question in the context of a rating prediction service based on matrix factorization. We construct a protocol of interactions between the service and users that has remarkable optimality properties: it is privacy-preserving, in that no inference algorithm can succeed in inferring a user's private attribute with a probability better than random guessing; it has maximal accuracy, in that no other privacy-preserving protocol improves rating prediction; and, finally, it involves a minimal disclosure, as the prediction accuracy strictly decreases when the service reveals less information. We extensively evaluate our protocol using several rating datasets, demonstrating that it successfully blocks the inference of gender, age and political affiliation, while incurring less than 5% decrease in the accuracy of rating prediction.
On the Dynamics of IP Address Allocation and Availability of End-Hosts
Oded Argon,Anat Bremler-Barr,Osnat Mokryn,Dvir Schirman,Yuval Shavitt,Udi Weinsberg
Computer Science , 2010,
Abstract: The availability of end-hosts and their assigned routable IP addresses has impact on the ability to fight spammers and attackers, and on peer-to-peer application performance. Previous works study the availability of hosts mostly by using either active pinging or by studying access to a mail service, both approaches suffer from inherent inaccuracies. We take a different approach by measuring the IP addresses periodically reported by a uniquely identified group of the hosts running the DIMES agent. This fresh approach provides a chance to measure the true availability of end-hosts and the dynamics of their assigned routable IP addresses. Using a two month study of 1804 hosts, we find that over 60% of the hosts have a fixed IP address and 90% median availability, while some of the remaining hosts have more than 30 different IPs. For those that have periodically changing IP addresses, we find that the median average period per AS is roughly 24 hours, with a strong relation between the offline time and the probability of altering IP address.
The Extent of Mathematical Creativity and Aesthetics in Solving Problems among Students Attending the Mathematically Talented Youth Program  [PDF]
Einav Aizikovitsh-Udi
Creative Education (CE) , 2014, DOI: 10.4236/ce.2014.54032

This study investigates the extent of mathematical creativity among 57 eight-grade talented students in the Mathematically Talented Youth Program. We examine the reasoning these students applied in solving a problem; the degree of mathematical creativity and aesthetic in their approach in solving a non-routine mathematical problem; and explore whether the students’ mathematical thinking is dependent solely upon previous mathematical knowledge and skills. We found that majority of the students relied on technical algorithm to solve the problem. Although talented students coped well with the thinking challenge, most of them operated at the basic level of creativity. One implication drawn from this study is the need to broaden and develop mathematical-logical thinking both as specific lessons and also as an integral part of other lessons in the program.

Igualdad de oportunidades y autonomía familiar
An??lisis filos?3fico , 2007,
Abstract: this essay analyzes the problem of the normative incompatibility between two principles which are widely accepted by liberals -the principle of equality of opportunities and that of family autonomy- and this within the framework of rawls′s theory of justice. after specifying different ways in which the autonomy of the family necessarily leads to inequality of opportunities between individuals, i examine two different solutions suggested by rawls in a theory of justice and i intend to demonstrate why they are wrong.
Justicia versus caridad en la teoría de la propiedad de Locke
Juliana Udi
Revista Latinoamericana de Filosofía , 2012,
Abstract: En el presente trabajo identifico dos conceptos diferentes de justicia en los escritos de Locke -"justicia propietaria" y "justicia como imparcialidad"- y examino el modo en que cada uno de ellos se vincula con la caridad. Me propongo poner de relieve cómo, en ambos casos, Locke exige que frente a un conflicto de principios prevalezca la caridad. Esto permite matizar la interpretación de Locke como defensor de la apropiación ilimitada y suma elementos de juicio para considerar, en cambio, que su teoría no excluye la convalidación de un esquema redistributivo tendiente a garantizar el bienestar material mínimo de los noapropiadores. In this paper I identify two different lockean concepts of justice - "proprietary justice" and "justice as fairness" - and examine the relationship between each of them and charity in John Locke′s theory of property. As I try to show, in both cases Locke considers that charity may have priority over justice. This undermines the classical interpretation of Locke as a defender of unlimited capitalistic appropriation and provides additional evidence supporting Locke′s acceptation of a minimal redistributive system which should guarantee the material welfare of non-appropriators.
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