Section: New Results
Network Algorithms and Analysis
Bounds on the Cover Time in the Rotor-Router Model
In [23] and [33] , we
consider the rotor-router mechanism, which provides a deterministic
alternative to the random walk in undirected graphs. In this model, a set of
In [23] , we provide tight bounds on the cover time of
In [33] , we perform a case study of cover time of the
rotor-router, showing how the cover time depends on
Web Ranking and Aliveness
In [29] and [30] , we investigate how to efficiently retrieve large portions of alive pages from an old crawl using orderings we called LiveRanks. Our work establishes the possibility of efficiently recovering a significant portion of the alive pages of an old snapshot and advocates for the use of an adaptive sample-based PageRank for obtaining an efficient LiveRank. Additionally, application field is not limited to Web graphs. It can be straightforwardly adapted to any online data with similar linkage enabling crawling, like P2P networks or online social networks.
Wireless Positioning
In [31] , we consider how to construct a low-cost and efficient positioning system. We have proposed a new method called Two-Step Movement (2SM) to estimate the position of Mobile Terminal (MT). By exploiting useful information given by the position change of the device or user movement, this method can minimize the number of Reference Points (RP) required (i.e., only one) in a localization system or navigation service and reduce system implementation cost. Analytical result shows that the user position can be derived, under noisy environment, with an estimation error about 10% of the distance between the RP and MT, or even less.
Content Centric Networking
Today's Internet usage is mostly centered around location-independent services. Because the Internet architecture is host-centric, content or service requests still have to be translated into locations, or the IP address of their hosts. This translation is realized through different technologies, e.g. DNS and HTTP redirection, which are currently implemented at the Application Layer. (ICN) proposes to evolve the current Internet infrastructure by extending the networking layer with name-based primitives.
In [45] , we target the design and implementation of a content router, which is a network entity that implements name-based forwarding, or it can forward packets based on the content name they are addressed to. This work makes three major contributions. First, we propose an algorithm for name-based longest prefix match whose main novelty is the prefix Bloom filter, a Bloom filter variant that exploits the hierarchical nature of content prefixes. Second, a content router design that is compatible with both today's networking protocols and with widely used network equipments. Third, two innovative features that increase the scalability of a content router both in term of forwarding-information-base size and forwarding speed.
In the demonstration [34] held in the ICN conference, we demonstrate a high speed Information-Centric Network in a mobile backhaul setting. In particular, we emulate an information aware data plane and we highlight the significant benefits it provides in terms of both user experience and network provider cost in the backhaul setting. Our setup consists of high-speed ICN devices employed in a down-scaled realistic representation of a mobile backhaul topology, fed with traffic workloads characterized from Orange's mobile network. We compare numerical results activating and de-activating the ICN feature at run-time, showing the main differences between the two approaches. All the devices are implemented in a real high-speed multi-core equipment, and they are connected by means of internal port connections. Traffic is injected using a Traffic Generator which is implemented in the same architecture.
Information Dissemination
Dissemination with Noise or Limited Memory
In [26] , we introduce the study of basic distributed computing problems in the context of noise in communication. We establish tight and almost tight bounds for the rumor spreading problem as well as for the majority-consensus problem.
In [11] , we theoretically study a general model of information sharing within animal groups. We take an algorithmic perspective to identify efficient communication schemes that are, nevertheless, economic in terms of communication, memory and individual internal computation. We present a simple and natural algorithm in which each agent compresses all information it has gathered into a single parameter that represents its confidence in its behavior. Confidence is communicated between agents by means of active signaling. We motivate this model by novel and existing empirical evidences for confidence sharing in animal groups. We rigorously show that this algorithm competes extremely well with the best possible algorithm that operates without any computational constraints. We also show that this algorithm is minimal, in the sense that further reduction in communication may significantly reduce performances. Our proofs rely on the Cramér-Rao bound and on our definition of a Fisher Channel Capacity. We use these concepts to quantify information flows within the group which are then used to obtain lower bounds on collective performance.
Gossip and Rumor Spreading with Flooding
In [2] , we address the flooding problem in
dynamic graphs, where flooding is the basic mechanism in which every node
becoming aware of an information at step
Small-world Networks
In [9] , we study decentralized routing in small-world
networks that combine a wide variation in node degrees with a notion of spatial
embedding. Specifically, we consider a variant of J. Kleinberg's grid-based
small-world model in which (1) the number of long-range edges of each node is
not fixed, but is drawn from a power-law probability distribution with exponent
parameter
Voting Systems and Path Selection in Networks
In [24] , we apply our theoretical and experimental results on voting systems to a network use case: choosing a path in a network. In our model, nodes have an economical reward or cost for each possible path and they vote to elect the path. We show that the choice of the voting system has an important impact on the manipulability and the economical efficiency of this system. From both points of view, Instant-Runoff Voting gives the best results.