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We examine the fundamental properties that determine the basic performance metrics for opportunistic communications. We first consider the distribution of inter-contact times between mobile devices. Using a diverse set of measured mobility traces, we find as an invariant property that there is a characteristic time, order of half a day, beyond which the… (More)

Motivated by the study of peer-to-peer file swarming systems à la BitTorrent, we introduce a probabilistic model of <i>coupon replication systems</i>. These systems consist of users, aiming to complete a collection of distinct coupons. Users are characterised by their current collection of coupons, and leave the system once they complete their coupon… (More)

— We define " random trip", a generic mobility model for independent mobiles that contains as special cases: the random waypoint on convex or non convex domains, random walk with reflection or wrapping, city section, space graph and other models. We use Palm calculus to study the model and give a necessary and sufficient condition for a stationary regime to… (More)

We consider unicast equation-based rate control, where a source estimates the loss event ratio $p$, and, primarily at loss events, adjusts its send rate to $f(p)$. Function $f$ is assumed to represent the loss-throughput relation that TCP would experience. When no loss occurs, the rate may also be increased according to some additional mechanism. We assume… (More)

Balanced graph partitioning in the streaming setting is a key problem to enable scalable and efficient computations on massive graph data such as web graphs, knowledge graphs, and graphs arising in the context of online social networks. Two families of heuristics for graph partitioning in the streaming setting are in wide use: place the newly arrived vertex… (More)

— We consider a simple model of parallel TCP connections defined as follows. There are N connections competing for a bottleneck of fixed capacity. Each connection is assumed to increase its send rate linearly in time in absence of congestion indication and otherwise decreases its rate to a fraction β of the current send rate. Whenever aggregate send rate of… (More)

We consider epidemic-style information dissemination strategies that leverage the nonuniformity of host distribution over subnets (e.g., IP subnets) to optimize the information spread. Such epidemic-style strategies are based on random sampling of target hosts according to a sampling rule. In this paper, we consider the metric of total number of samplings… (More)

We describe a seriation algorithm for ranking a set of n items given pairwise comparisons between these items. Intuitively, the algorithm assigns similar rank-ings to items that compare similarly with all others. It does so by constructing a similarity matrix from pairwise comparisons, using seriation methods to reorder this matrix and construct a ranking.… (More)

This paper aims to quantify two common assumptions about social tagging: (1) that tags are "meaningful" and (2) that the tagging process is influenced by tag suggestions. For (1), we analyze the semantic properties of tags and the relationship between the tags and the content of the tagged page. Our analysis is based on a corpus of search keywords,… (More)

We study the effectiveness of automatic patching and quantify the speed of patch dissemination required for worm containment. We focus on random scanning as this is representative of current generation worms, though smarter strategies exist. We find that even such "dumb'' worms require very fast patching. Our primary focus is on how delays due to worm… (More)