Alberto Negro

F-Chord: Improved Uniform Routing on Chord

We propose a family of novel schemes based on Chord retain- ing all positive aspects that made Chord a popular topology for routing in P2P networks. The schemes, based on the Fibonacci number system, allow to improve on the maximum/average number of hops for lookups and the routing table size per node.

Ulam's searching game with three lies

In this paper we determine the minimal number of yes-no queries needed to find an unknown integer between 1 and 2^m if at most three of the answers may be erroneous.

Efficient distributed selection with bounded messages

We consider the problem of selecting the Kth smallest element of a set distributed among the sites of a communication network when the size of messages is bounded; that is, each message is a packet which contains at most c bits, where c/spl ges/1 is a constant. A general selection algorithm using packets is presented and its packet complexity is analyzed. Its complexity is shown to be a significant improvement for a large range of packet sizes over the existing bounds. The proposed technique is then instanciated for specific classes of network topologies; the resulting bounds either match or improve the ones of existing solutions for a large range of values of the packet size. Furthermore, it is bit optimal in star networks.

GAS: Group Adaptive System

This paper describes an ongoing research project to design a Group Adaptive System (GAS) for collaborative navigation on the web. Our objective is to provide information that adapts to web users based on automatically determined, dynamic user groups. To do this, our approach takes into account the structure of the web (using the CLEVER algorithm [16]) and user interactions when navigating the web (gathered by our collaborative environment) to offer users in a consistent information space determined by their interests and activities. In the end, our system, GAS, enables users to perform asynchronous collaborative navigation by combining resources discovered by a group of users and suggestions discovered by the CLEVER algorithm to provide recommendations to the group.

Multimodal monitoring of Web servers

We present a multimodal real-time monitoring system called MMM that describes server activity by multimodal representation and supplements traditional ways of conveying sonification and peripheral information to Webmasters. We also describe a prototype and plug-in that MMMs three-level distributed architecture implements.

CHEOPS: Adaptive Hypermedia on World Wide Web

Because of stateless characteristics of http, it is not possible for http servers to adapt responses on the basis of previous interactions with the same user. Although efficient, this is a limiting aspect of the protocol, particularly for Web documents that are directed toward a broad audience, including experts and novices and an adaptive response would be helpful in providing information with the right style.

Solution of Ulam's problem on binary search with three lies

Abstract In this paper we determine the minimal number of yes-no queries needed to find an unknown integer between 1 and 1000000 if at most three of the answers may be erroneous.

Non-uniform deterministic routing on F-Chord(/spl alpha/)

In this paper, we present a family of novel P2P routing schemes based on Chord (and its variation F-Chord(/spl alpha/) that trades off uniformity with efficiency without using any additional overhead. We prove that H-F-Chord(/spl alpha/)s routing is more efficient than in F-Chord(/spl alpha/) in terms of its average path length that is O(log n/ log log n). We also show, by simulations, that H-F-Chord(/spl alpha/) is more efficient than the corresponding F-Chord(/spl alpha/) by a percentage that goes from 15% to 22% even for small n.

Mobile phone batteries draining: Is green web browsing the solution?

Providing mechanisms to improve energy efficiency of mobile devices is, in the past few years, one of the important objectives in the field of green computing and energy savings. Several studies have addressed this issue from different point of views, i.e., hardware, software, as well as by analyzing the energy drained by different mobile applications. On the other hand, the energy consumption of Web browsing activities has been poorly addressed, given the lack of analysis about users real browsing sessions. We propose in this paper a new methodology that exploits an hardware-based instrumentation to measure energy savings in mobile devices when switching on/off filtering techniques offered by a privacy-enhancing technology. We discuss an extensive experimental study that shows how privacy-preserving mechanisms can help users to protect their privacy, their personal information, and en passant efficiently reduce communication and computation overhead and thus battery consumption.

Degree-Optimal Routing for P2P Systems

AbstractnWe define a family of Distributed Hash Table systems whose aim is to combine the routing efficiency of randomized networks—e.g. optimal average path length O(logu20092n/δlogu2009δ) with δ degree—with the programmability and startup efficiency of a uniform overlay—that is, a deterministic system in which the overlay network is transitive and greedy routing is optimal. It is known that Ω(logu2009n) is a lower bound on the average path length for uniform overlays with O(logu2009n) degree (Xu et al., IEEE J. Sel. Areas Commun. 22(1), 151–163, 2004).nnOur work is inspired by neighbor-of-neighbor (NoN) routing, a recently introduced variation of greedy routing that allows us to achieve optimal average path length in randomized networks. The advantage of our proposal is that of allowing the NoN technique to be implemented without adding any overhead to the corresponding deterministic network.nnWe propose a family of networks parameterized with a positive integer c which measures the amount of randomness that is used. By varying the value c, the system goes from the deterministic case (c=1) to an “almost uniform” system. Increasing c to relatively low values allows for routing with asymptotically optimal average path length while retaining most of the advantages of a uniform system, such as easy programmability and quick bootstrap of the nodes entering the system.nnWe also provide a matching lower bound for the average path length of the routing schemes for any c.n