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Séminaire INFRES TELECOM ParisTech / LINCS, Salle du conseil (23 av. d’Italie 75013 Paris) Speaker : de 14h à 15h M. Zukerman (University of Hong Kong) Talk : Modeling and blocking probability evaluation for multi-priority circuit switched optical networks Abstract: It is expected that circuit switching (CS) will play an important major role in future optical networks. CS normally does not require buffering which is very costly in the optical domain. If the traffic on a CS network is well managed CS networks can guarantee quality of service (QoS) to customers in a way that can even lead to efficient link utilization and low consumption of energy per bit. In the core Internet, where traffic is heavily multiplexed, it is easier to achieve high utilization and therefore the role of CS at the core is clearly important. However, CS can also lead to a green and efficient operation end-to-end for large bursts of data. Accurate, robust and scalable blocking probability evaluation is an important element in CS traffic management. We consider an optical network that uses various circuit-switching based technologies such as OCS and OFS. We model it as two-priority circuit-switched network with non-hierarchical alternate routing. We evaluate the blocking probability using algorithms based on the Erlang Fixed-point Approximation (EFPA) and the Overflow Priority Classification Approximation (OPCA). For a particular example of a 6-node fully meshed network with alternate routing, we compare numerically between OPCA over EFPA and discuss traffic implications. Speaker : à 15h à 16h M. Gagnaire, joint work with E. Doumith and S. Al Zahr (Telecom-ParisTech) Talk : Mutual Impact of Traffic Correlation and Regenerator Concentration in Translucent WDM Networks Abstract: Since the early 2000s, a real attention is paid to physical impairments arising in large-scale optical networks. One cost-effective solution to cope with transmission impairments is to deploy 3R (re-amplifying, re-shaping, and re-timing) regenerators in a limited number of network nodes (i.e., translucent networks).Taking into account the simultaneous effect of four transmission impairments (amplified spontaneous emission, chromatic dispersion,polarization mode dispersion, and non linear phase shift), we propose a novel exact approach for impairment-aware network planning. In contrast with previous works, we investigate the problem under pre-planed dynamic traffic. Our proposal takes advantage of the dynamics of the traffic pattern so that regeneration resources may be shared among non-concurrent requests.Given a network topology and a set of pre-planned requests, we target the minimum number of regenerators or/and regeneration sites. Thanks to an ILP formulation of this problem, we outline through the obtained numerical results the mutual impact between the time-correlation of the requests and the level of regenerators’ concentration. Séminaire INFRES TELECOM ParisTech / Amphi Saphir Speaker : à 14h Venkat Anantharam (UC Berkeley) Talk : Anonymity via networks of mixes Abstract: Mixes are relay nodes that accept packets arriving from multiple sources and release them after variable delays to prevent an eavesdropper from associating outgoing packets to their sources. We assume that each mix has a hard latency constraint. Using an entropy-based measure to quantify anonymity, we analyze the anonymity provided by networks of such latency-constrained mixes. Our results are of most interest under light traffic conditions. A general upper bound is presented that bounds the anonymity of a single-destination mix network in terms of a linear combination of the anonymity of two-stage networks. By using a specific mixing strategy, a lower bound is provided on the light traffic derivative of the anonymity of single-destination mix networks. The light traffic derivative of the upper bound coincides with the lower bound for the case of mix-cascades (linear single-destination mix networks).
Séminaire INFRES TELECOM ParisTech / Amphi Saphir Speaker : à 14h Pierre Latouche (candidat à mic2) Talk : Modèles de graphe aléatoire à classes chevauchantes pour l’analyse des réseaux Abstract: Les réseaux sont largement utilisés dans de nombreux domaines scientifiques afin de représenter les intéractions entre objets d’intérêt. Ainsi, en biologie, les réseaux de régulation s’appliquent à décrire les mécanismes de régulation des gènes, à partir de facteurs de transcription, tandis que les réseaux métaboliques permettent de représenter des voies de réactions biochimiques. En sciences sociales, ils sont couramment utilisés pour Speaker : à 15h15 Philippe Gambette (candidat à mic2) Talk : Problèmes d’optimisation combinatoire pour la reconstruction de réseaux phylogénétiques Abstract:Les réseaux phylogénétiques généralisent le modèle de l’arbre pour décrire l’évolution des espèces, en permettant à des arêtes entre les branches de l’arbre d’exprimer des échanges de matériel génétique entre espèces coexistantes. De nombreuses approches combinatoires - Je présenterai plusieurs problèmes d’optimisation combinatoire sur les réseaux phylogénétiques, concernant leur reconstruction à partir de triplets ou de clades. Je décrirai des méthodes de résolution basées sur des algorithmes exacts (de complexité paramétrée notamment) ou des heuristiques. |
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