Internet routing paths stability model and relation to forwarding paths

Analysis of real datasets to characterize the local stability properties of the Internet routing paths suggests that extending the route selection criteria to account for such property would not increase the routing path length. Nevertheless, even if selecting a more stable routing path could be considered as valuable from a routing perspective, it does not necessarily imply that the associated forwarding path would be more stable. Hence, if the dynamics of the Internet routing and forwarding system show different properties, then one can not straightforwardly derive the one from the other. If this assumption is verified, then the relationship between the stability of the forwarding path (followed by the traffic) and the corresponding routing path as selected by the path-vector routing algorithm requires further characterization. For this purpose, we locally relate, i.e., at the router level, the stability properties of routing path with the corresponding forwarding path. The proposed stability model and measurement results verify this assumption and show that, although the main cause of instability results from the forwarding plane, a second order effect relates forwarding and routing path instability events. This observation provides the first indication that differential stability can safely be taken into account as part of the route selection process

Inferring Update Sequences in Boolean Gene Regulatory Networks

International audienceThis paper employs mathematical programming and mixed integer linear programming techniques for solving a problem arising in the study of geneticregulatory networks. More precisely, we solve the inverse problem consisting in the determination of the sequence of updates in the digraph representingthe gene regulatory network (GRN) of Arabidopsis thaliana in such a way that the generated gene activity is as close as possible to the observed data

Efficient Measurement of Complex Networks Using Link Queries

International audienceComplex networks are at the core of an intense research activity. However, in most cases, intricate and costly measurement procedures are needed to explore their structure. In some cases, these measurements rely on link queries: given two nodes, it is possible to test the existence of a link between them. These tests may be costly, and thus minimizing their number while maximizing the number of discovered links is a key issue. This is a challenging task, though, as initially no information is known on the network. This paper studies this problem: we observe that properties classically observed on real-world complex networks give hints for their efficient measurement; we derive simple principles and several measurement strategies based on this, and experimentally evaluate their efficiency on real-world cases. In order to do so, we introduce methods to evaluate the efficiency of strategies. We also explore the bias that different measurement strategies may induce

Revealing intricate properties of communities in the bipartite structure of online social networks

International audienceMany real-world networks based on human activities exhibit a bipartite structure. Although bipartite graphs seem appropriate to analyse and model their properties, it has been shown that standard metrics fail to reproduce intricate patterns observed in real networks. In particular, the overlapping of the neighbourhood of communities are difficult to capture precisely. In this work, we tackle this issue by analysing the structure of 4 different real-world networks coming from online social activities. We first analyse their structure using standard metrics. Surprisingly, the clustering coefficient turns out to be less relevant than the redundancy coefficient to account for overlapping patterns. We then propose new metrics, namely the dispersion coefficient and the monopoly, and show that they help refining the study of bipartite overlaps. Finally, we compare the results obtained on real networks with the ones obtained on random bipartite models. This shows that the patterns captured by the redundancy and the dispersion coefficients are strongly related to the real nature of the observed overlaps

Inferring Parameters in Genetic Regulatory Networks

International audienceWe formulate and solve the problem of determining the arc weights in a Genetic Regulatory Network (GRN) so that it presents observed states at given development stages

Inferring Parameters in Genetic Regulatory Networks

International audienceWe formulate and solve the problem of determining the arc weights in a Genetic Regulatory Network (GRN) so that it presents observed states at given development stages

Proceedings of the 8th Cologne-Twente Workshop on Graphs and Combinatorial Optimization

International audienceThe Cologne-Twente Workshop (CTW) on Graphs and Combinatorial Optimization started off as a series of workshops organized bi-annually by either Köln University or Twente University. As its importance grew over time, it re-centered its geographical focus by including northern Italy (CTW04 in Menaggio, on the lake Como and CTW08 in Gargnano, on the Garda lake). This year, CTW (in its eighth edition) will be staged in France for the first time: more precisely in the heart of Paris, at the Conservatoire National d’Arts et Métiers (CNAM), between 2nd and 4th June 2009, by a mixed organizing committee with members from LIX, Ecole Polytechnique and CEDRIC, CNAM

Inferring Parameters in Genetic Regulatory Networks

International audienceWe formulate and solve the problem of determining the arc weights in a Genetic Regulatory Network (GRN) so that it presents observed states at given development stages

UDP PING: a dedicated tool for improving measurements of the Internet topology

International audienceThe classical approach for Internet topology measurement consists in collecting as much data as possible and in constructing from it a view of the topology by merging the obtained data. Although this approach may seem reasonable, in most cases network measurements give partial views of the networks under concern, contain erroneous data, and may moreover be intrinsically biased. Here we present a new tool, namely UDP PING, that relies on a very different approach for the measurement of the Internet topology. We show the principles on which it relies and how to use it to deploy real worldwide measurements for obtaining a reliable estimation of the real degree distribution of routers in the core Internet