Mascotteis a joint team between INRIA Sophia Antipolis Méditerranée and the laboratory I3S (Informatique Signaux et Systèmes de Sophia Antipolis) which itself belongs to CNRS (Centre National de la Recherche Scientifique) and UNS (University of Nice Sophia Antipolis). Its research fields are Algorithmics, Discrete Mathematics, Combinatorial Optimization and Simulation, with applications to telecommunication networks.

The objectives of the Mascotteproject-team are to design networks and communication algorithms. In order to meet these objectives, the team studies various theoretical tools, such as Discrete Mathematics, Graph Theory, or Algorithmics and develops applied techniques and tools, especially for Combinatorial Optimization and Computer Simulation. In particular Mascotteused in the last years both these theoretical and applied tools for the design of various networks, such as WDM, wireless (radio), satellite, overlay, and peer-to-peer networks. This research has been done within various industrial and international collaborations.

This results also in the production of advanced softwares such as Grph, DRMSim, the Mascoptlibrary ( Mascotteoptimization), and ambitious software projects such as the OSA (Open Simulation Architecture) Computer Simulation Architecture.

The project develops tools and theory in the following domains: Discrete Mathematics (in particular Graph Theory), Algorithmics, Combinatorial Optimization and Simulation.

Typically, a telecommunication network (or an interconnection network) is modeled by a graph. A vertex may represent either a processor or a router or any of the following: a switch, a radio
device, a site or a person. An edge (or arc) corresponds to a connection between the elements represented by the vertices (logical or physical connection). We can associate more information
both to the vertices (for example what kind of switch is used, optical or not, number of ports, equipment cost) and to the edges (weights which might correspond to length, cost, bandwidth,
capacity) or colors (modeling either wavelengths or frequencies or failures) etc. Depending on the application, various models can be defined and have to be specified. This modeling part is an
important task. To solve the problems, we manage, when possible, to find polynomial algorithms. For example, a maximum set of disjoint paths between two given vertices is by Menger's theorem
equal to the minimum cardinality of a cut. This problem can be solved in polynomial time using graph theoretic tools or flow theory or linear programming. On the contrary, determining whether
in a directed graph there exists a pair of disjoint paths, one from

Graph coloring is an example of concept which appears in various contexts: WDM networks where colors represent wavelengths, radio networks where colors represent frequencies, fault tolerance where colors represent shared risk resource groups, and scheduling problems. Another tool concerns the development of new algorithmic aspects like parameterized algorithms.

In the last year the main application domain of the project remained Telecommunications. Within this domain, we consider applications that follow the needs and interests of our industrial partners, in particular Orange Labsor Alcatel-Lucent Bell-Labs, but also SMEs like 3-Roamand Avisto.

Mascotteis mainly interested in the design and management of heterogeneous networks. The project has kept working on the design of backbone networks (optical networks, backhaul and mesh (wireless) networks, and peer to peer networks).

The project has also been working on routing algorithms such as dynamic and compact routing schemes in the context of the STREP EULER leaded by Alcatel Lucent Bell Labs(Belgium). It also studied the evolution of the routing in case of any kind of topological modifications (maintenance operations, failures, capacity varaitions, etc.). Finally, an emphasis is done on green networks with low power consumption. This work is in collaboration with Orange Labsand the SME 3-Roamand partly supported by the ANR DIMAGREEN.

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Around 20,000 lines of code, developed in Java.

The Grphproject takes over Dipergrafs which was introduced in the activity report of 2010. A drastic change in the model of Dipergrafs justified the name change.

The objective of Grphis to provide researchers and engineers a suitable graph library for graph algorithms experimentation and network simulation. Grphis mainly a software library, but it also comes with a set of executable files for user interaction and graph format conversion; as such, it can be used autonomously. Performance and accessibility are the primary targets of the Grphlibrary. At every stage, it is designed to be efficient in terms of: computation time (use of parallelism, caching, adequate data structures, native code, etc.); memory requirements (use of Java primitives); and portability (it is written in a Java and C). Its model considers mixed graphs composed of (un)directed simple- and hyper-edges. It can handle large dynamic graphs in the order of millions of nodes. Grphcomes with a collection of base graph algorithms which are regularly augmented.

So far, most known users of the
Grphlibrary are part of INRIA and of the FP7 STREP EULER project.
Grphis distributed under the terms of a license defined by its contributors and is available for download. This license allows free usage and access
to the source code. See
http://

In 2011, Grphwas augmented over Dipergrafs of a number of features suited to its usage within the Mascotteresearch team. These include: addition of numerous graph manipulation methods; introduction of an incidence-list data structure for the representation of graphs; introduction of an adaptive data structure for the representation of sets (based on hash-tables and bit-vectors); integration of implementations of "maximum clique" and "sub-graph isomorphism" algorithms by Christine Solnon (CNRS, INSA Lyon). These sources, written in C, are compiled on-the-fly; integration of implementation of "graph isomorphism" algorithm by Brendan McKay (Australian National University); iteration of implementation of "number of triangles" algorithm by Matthieu Latapy (LIP6); introduction of a bridge to the Mascopt/OpenGVE library; introduction of a bridge to the JUNG library; addition of numerous graph algorithms; introduction of a new layer atop Grphwhich allows the representation and manipulation of graph as Java objects, like it is done in other libraries such as Mascopt, Jung, etc.; introduction of an efficient mechanism for the definition of graph properties; addition of graph reporting facilities.

On-going works concern the distributed execution of graph algorithms, a bridge to Sage, and the graphical edition of graphs.

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Around 45,000 lines, developed in Java, collaboration between MASCOTTE and researchers in LaBRI (95

The expansion of the Internet results in a number of issues: BGP (Border Gateway Protocol) starts to show its limits in terms of the number of routing table entries it can manage. More efficient dynamic routing protocols are thus under investigation. However, because deploying under-development routing protocols on the Internet is not practicable at a large-scale, simulation is a necessary step to validate the properties of a newly proposed routing scheme. Unfortunately, the simulation of routing protocols over large networks poses real challenges due to the limited computational capabilities of computers. Existing simulation tools exhibit limitations in terms of the number of nodes they can handle and of the models they propose. This motivated us to conceive and develop DRMSim (Dynamic Routing Model Simulator): a network simulator which addresses the specific problem of large-scale simulations of routing models.

DRMSim relies on a discrete-event simulation engine. It proposes a general routing model which accommodates any network configuration. Aside to this, it includes specific models for Generalized Linear Preference (GLP), and K-chordal network topologies, as well as implementations of routing protocols, including the routing protocol proposed in and lightweight versions of BGP (Border Gateway Protocol).

Recent developments (in 2011) in the DRMSim simulator include the four following elements:

1. The initial framework was composed of a routing model. It now incorporates a system model and a metric model. In addition, the system model now considers the dynamic evolution of the simulated network. This dynamic behavior includes the maintenance operations on the network infrastructure as well as router failures. This model stores the connectivity of routers and links before their failure is simulated. This information is used for the simulation of the recovery procedure. This model takes as its input parameter the distribution of failure probability for both routers and links.

2. The metric model has been fully rewritten and is now geared towards computational performance and flexibility. Taking measures along a discrete-event simulation can be performed in many ways. DRMSim uses a new approach which consists in a metric model listening to the simulation and system models. The user can define its own metrics. Memory and CPU usages depend on which metrics are defined, to which set of routers/links they are applied, how many measures are taken and their computational complexity. It is possible to restrict the model to a small amount of nodes/links by selectors provided as input parameters. At the cost of memory and CPU usage, metrics measures can be stored as time-ordered sequence of values. To reduce the need of resources, a single global measure for each metric can be computed. Finally, metrics can be computed globally on the set of selected entities (links/routers) but also separately for each entity.

3. DRMSim enables the definition of customized simulation scenarios and stateful simulation campaigns.

Commonly, a simulation campaign consists in iterating over the set of combinations of parameter values, calling the simulation function for every combination. These combinations cannot be found randomly nor can they be determined using linear functions. Indeed, most of the time there exist correlations between the parameters involved. Also for performance reasons, the end-user will prefer non-linear (most often logarithmic) evolutions for the values of the parameters. The definition of the set of combinations is strongly linked to the simulated system and the time needed to solve it. DRMSim provides a simulation methodology that describes (programmatically) the way a simulation campaign should be conducted.

The duration of a simulation can be as long as several hours (or days). In the context of a simulation campaign where numerous simulations are executed, it is important that re-starting a simulation campaign that was interrupted does not entail the re-computation of already computed results. In order to do this, DRMSim stores on disk every step of the execution of a simulation campaign.

In a simulation campaign, simulation runs are independent (no simulation depends on the result computed by another simulation). Consequently they can be executed in parallel. Because one simulation is most likely to use large amount of memory and to be multi-threaded, parallelizing the simulation campaign on one single computer is a poor parallelization scheme. Instead, we currently work at enabling the remote parallel execution of several simulation runs, with the same distribution framework that is used in the Grphlibrary.

4. Finally, DRMSim manipulates graph abstractions, allowing the user to force the use of a library different from the default one, i.e. Grph.

See also the web page
http://

Developed in Java.

Mascopt(
MascotteOptimization) is a Java library distributed under the terms of the LGPL license which is dedicated to graph and network processing.
Mascoptincludes a collection of Java interfaces and classes that implement fundamental data structures and algorithms. The forthcoming public
distribution of
Mascoptwill appear under the name of the
openGVEproject,
Mascoptbeing one implementation of the bridge graph interface (see
http://

The main objective of Mascoptproject is to ease software development in the field of network optimization. Examples of problems include routing, grooming, survivability, and virtual network design. Mascopthelps implementing a solution to such problems by providing a data model of the network and the demands, classes to handle data and ready to use implementations of existing algorithms or linear programs (e.g. shortest paths or integral multicommodity flow).

A key feature of Mascoptis to provide a generic linear programming object interface which allows users to program the same way whether the target solver is IBM ILOG CPLEX, GLPK (GNU Linear Programming Kit) or CLP/CBC (accessed through JNI).

Mascopthas been intensively used in the past within Mascotteindustrial cooperation programs for experimentation and validation purposes as for example with Alcatel Space Technologies and Orange Labs. Today, the library is used within the framework of the ANR AGAPE to implement FPT algorithms (work done at LIFO).

See also the web page
http://

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Developed in Java (

Component-based modeling has many well-known good properties. One of these properties is the ability to distribute the modeling effort amongst several experts, each having his/her own area of system expertise. Clearly, the less experts have to care about areas of expertise of others, the more efficient they are in modeling sub-systems in their own area. Furthermore, the process of studying complex systems using discrete-event computer simulations involves several areas of non-system expertise, such as discrete-event techniques or experiment planning.

The Open Simulation Architecture (OSA) is designed to enforce a strong separation of the end-user roles and therefore, ensure a successful cooperation of all the experts involved in the process of simulating complex systems.

The OSA architecture is also intended to meet the expectations of a large part of the discrete-event simulation community: it provides an open platform intended to support researchers in a wide range of their simulation activities, and allows the reuse and sharing of system models in the simulation community by means of a flexible and generic component model (Fractal).

Many discrete-event simulators are developed concurrently, but with identical or similar purpose. Another goal of OSA is to favor the reuse and integration of simulation software components and models. To favor reuse, OSA uses a layered approach to combine the modeling, simulation, and related concerns, such as instrumentation or deployment. This ability is demonstrated by the successful integration and reuse of third-party components, such as Scave, the analysis module of Omnet++, or a large number of the James II plugins developed by the University of Rostock. OSA is both a testbed for experimenting new simulation techniques and a tool for real case studies.

OSA is Open Source (LGPL) and is available for download on the INRIA forge server
http://

See also the web page
http://

Developed in Python, Cython, and C++. N. Cohen wrote more than 180 patches and N. Cohen, D. Coudert and L. Sampaio reviewed more than 120 others for inclusion in Sage.

Sagemath is a free open-source mathematics software aiming at becoming an alternative to Maple and Matlab. Initially created by William Stein (Professor of mathematics at Washington University), Sagemath is currently developed by more than 180 contributors around the world (mostly researchers). It has currently more than 200 MB of source code and the graph module consists of 40,000 lines. It was initially of interest for Mascotte because of its large library in Combinatorics and Graph Theory. This year, impressive improvements have been made to this library. In particular, N. Cohen contributed a lot into the following: 1) implementation of a generic interface between Sage and existing (Mixed Integer) Linear Program solvers, 2) implementation of exact algorithms for common Polynomial/NP-Complete graph problems, often through the use of Linear Programs, and 3) improving Sage's documentation by participating to the writing of a french manual on the use of Sage with 10 other french scientists. New patches are in preparation in the group for possible inclusion in Sage.

Sage's Graph and Linear Programing libraries are currently used by Mascotte members to test algorithms or compare their performances, as well as to prove/disprove theoretical conjectures and for teaching purposes in the Master IFI, stream UBINET.

More than 5,000 lines, developed in Java.

Java4unix proposes a development and distribution framework which simplifies the use of Java for UNIX software programming/distribution. Until now, Java could hardly be used for the development UNIX applications because invoking Java applications from the UNIX shell must be done through an explicit call to the Java virtual machine and writing simple things in Java often requires long coding. Java4unix aims at filling those two gaps by providing a UNIX installer for java applications, turning them to standard UNIX application and a framework that UNIX programmers may use to manipulate files/text, etc.

Java4unix includes a module which enables the reporting and automatic releasing of Eclipse Java projects. This module was formely separated from Java4unix and was referred to as EPR.

See also the web page
http://

Developed in Java.

Many mathematical and engineering problems can be expressed as linear programs, and doing so facilitates their resolution. Indeed it is generally more convenient to transform a domain-specific problem into a linear-optimizable one (that can be solved by any solver) rather than writing a complex domain-specific algorithm. In the case of graph theory, problems like flows, minimum vertex cover, maximum stable can be conveniently represented via linear programs.

Jalinopt is a Java toolkit for building and solving linear programs. It consists of a straightforward object-oriented model for linear programs, as well as a bridge to most common solvers, including GLPK and CPLEX.

Altought Jalinopt is inspired by Mascopt and JavaILP, it provides a significantly different model and an utterly different approach to connecting to the solver. In particular this approach, based in inter-process piping, offers better portability, and the possibility to connect (via SSH) to solvers on remote computers.

See also the web page
http://

More than 1,500 lines, developed in Java.

JavaFarm is a middleware enabling the distribution of Java applications across farms of servers. Its workflow basically enables an application to locally aggregate code and data into an object, called job that will migrate to another computer, where it will be computed. When a job completes, its result is transferred back to the caller. Among other features, JavaFarm supports futures (asynchronous job executions), thereby enabling parallelization of the distributed code. The design objectives of JavaFarm are to make distribution and parallelism as transparent and easy as possible.

See also the web page
http://

Around 12,000 lines, developed in Java.

Mascsim is a distributed discrete event simulator whose main target is to be easy to use.

Unlike most discrete-event simulators, the researcher who is using Mascsim is required to provide only the bare minimum material needed for the simulation: a model for the system, a set of events describing what is going on in the system, as well as a set of metrics of interest.

The simulation process is then entirely automatized.

See also the web page
http://

Around 8,000 lines, developed in Python.

P2PVSim is a simple discrete-event simulator created for analyzing theoretical properties of peer-to-peer live video streaming algorithms. Implemented in Python it was designed with clarity and extensibility in mind from the beginning. It is capable of simulating overlays of a few thousands of peers. Multiple control protocols have been implemented. At the same time, a lot of work was put into the performance and scalability aspects of the software. Currently it is meant for simulating overlays of a few thousand peers running multiple control protocols that have been implemented.

Network design is a very wide subject that concerns all kinds of networks. We mainly study telecommunications networks which can be either physical networks (backbone, access, wireless, ...) or virtual (logical) ones. The objective is to design a network able to route a (given, estimated, dynamic, ...) traffic under some constraints (e.g. capacity) and with some quality of service (QoS) requirements. Usually the traffic is expressed as a family of requests with parameters attached to them. In order to satisfy these requests, we need to find one (or many) path(s) between their end nodes. The set of paths is chosen according to the technology, the protocol or the QoS constraints. For instance, optical backbones use the WDM technology to take better advantage of the capacity of the optical fibers often already installed. This is achieved through the multiplexing of several wavelength channels onto the same fiber. In that case a resource allocation is an optical channel, also called lightpath, which includes a path and wavelengths assigned to its links, one per link. If wavelength translation is performed in optical switching, then each channel may be assigned different wavelengths on the links of its path; otherwise the wavelength continuity imposes all the links to have the same wavelength. Of course, two lightpaths sharing a link must use different wavelengths on that link. The design can be done at the conception of the network (i.e. when conceiving a virtual network in MPLS where we have to establish virtual paths) or to adapt the network to changes (failures, new link, updates of routers, variation of traffic, ...). Finally there are various optimization criteria which differ according to the point of view: for a network user they are related to his/her satisfaction (minimizing delays, increasing available bandwidth, ...), while for a network operator, economics criteria like minimizing deployment and operating costs are more important.

This very wide topic is addressed by a lot of academic and industrial teams in the world. Our approach is to attack these problems with tools from Discrete Mathematics.

In a WDM network, routing a connection request consists in assigning to this request a route in the physical network and a wavelength. When each request uses at most

This year, we considered the minimization of the number of ADMs in optical WDM bidirectional rings, considering symmetric shortest path routing and all-to-all unitary requests
. We formulate the problem in terms of graph decompositions, and
state a general lower bound for all the values of the grooming factor

In production networks, traffic evolution, failures and maintenance operations force to adapt regularly the current configuration of the network (virtual topology, routing of
connections). The routing reconfiguration problem in WDM networks is thus to schedule the
*migration*of established lightpaths from current routing to a new pre-computed one while minimizing service disruptions. We have shown in the past the relations between this problem
and the
*graph searching problem*(see also Section
).

This year, we have continued studying the tradeoffs between the total number and the number of simultaneous interruptions that occurs during the reconfiguration process, proving in particular that the knowledge of one parameter does not help to optimize the other , . We have also started investigating the influence of physical layer impairment constraints on the reconfiguration problem . More precisely, using a new wavelength in a fiber of a WDM network forces to tune or recalibrate all already used wavelengths. We thus model the cost of using a new wavelength with a linear function of the number of already used wavelengths. We have then studied the problem of minimizing the cost of the reconfiguration according to this function. We have shown that this optimization problem is already NP-complete in a two-node network. We have also obtained general bounds and characterized instances for which the problem can be solved in polynomial time. We have additionaly proposed and evaluated heuristics.

The minimization of ICT (Information and Communications Technologies) energy consumption has become a priority with the recent increase of energy cost and the new sensibility of public, governments and corporations towards energy consumption. ICT alone is responsible of 2% to 10% (depending on the estimations) of the world power consumption. For example, it is estimated that switches, hubs, routers account for 6 TWh per year in the US.

Several studies exhibit that the traffic load of the routers only has a small influence on their energy consumption. Hence, the power consumption in networks is strongly related to the number of active network elements, such as interfaces, line cards, base chassis, etc. In , , we have defined and modeled formally the problem of finding a routing that minimizes the (weighted) number of active network elements. We have proved that this problem is not in APX, that is there is no polynomial-time constant-factor approximation algorithm to solve it. We have obtained general bounds for this problem, and bounds for particular topologies such as trees, grids, and cliques. We have also proposed a heuristic algorithm offering good performance on real topologies. Last, we have analyzed the impact of energy efficient routing on the stretch factor and on fault tolerance.

We have also studied potential energy savings in fixed broadband wireless networks , . See Section for more details.

IP multicast is a protocol that deals with group communications with the aim of reducing traffic redundancy in the network. However, due to difficulty in deployment and poor scalability with a large number of multicast groups, IP multicast is still not widely deployed nor used on the Internet. Recently, Xcast6 and Xcast6 Treemap, the two network layer multicast protocols, have been proposed with complementary scaling properties to IP multicast: they support a very large number of active multicast sessions. However, the key limitation of these protocols is that they only support small multicast groups. To overcome this limitation, we have proposed the Xcast6 Treemap Island , a hybrid model of Application Layer Multicast (ALM) and Xcast6 that can work for large multicast groups. Our model has several advantages: ease of deployment, efficiency in bandwidth savings, no control message between end-host and router, zero multicast forwarding state at router and no need for a multicast address allocation protocol. In addition, this model is a potential service from which an ISP (Internet Service Provider) can get new revenue. We have shown the feasibility of our model by simulation and comparison with IP multicast and NICE protocols.

Other results on multi-interface networks were obtained outside of Mascotte , , , , , , .

Mascottehas conducted an intense research effort on wireless access networks. From the technological and architectural point of view, the field is broad, from mesh (or multi-hop cellular) networks to ad-hoc and sensor networks. Nevertheless, many questions and approaches are generic from an algorithmic and structural prospect. In particular, we have considered three of the most prominent performance metrics for radio networks. Using combinatorial optimization and centralized algorithmic with a network design flavor, fast data gathering, call scheduling, transport capacity and energy consumption of the networks have been studied. Our approach is complementary with those developed in other INRIA project-teams such as Planete, Maestro, Swing, or Pops. The complementarity has been exploited through a joint Ph.D. between Maestroand Mascotte , through an ANR VERSO project in which Maestro, Mascotte, and Swingare involved, and through regular collaborations with Pops. At the international level, we cooperate with some groups in renowned research centers such as CTI of Patras in Greece, RWTH Aachen in Germany, Universities of Roma or Salerno in Italy, the Technion Institute in Israël, SFU in Vancouver, Canada, UFC Universidade Federal do Ceará, Fortaleza, Brazil, or the University of Sao Paulo in Brazil. We studied a wide range of issues of wireless networks, from the design of efficient cross-layer medium access, call scheduling and routing techniques to energy efficient optimization. We developed theoretical tools for integrating dynamic caracteristics of the networks in the optimization models, and analyzing and evaluating dynamic networks. Some graph coloring problems motivated by channel assignment in wireless networks are detailed in Section .

We have investigated network optimization problems related to the design and configuration of fixed wireless microwave backhaul - the portion of the network infrastructure that provides interconnectivity between the access and the core networks. Unlike wired networks, the capacity of a microwave radio link is prone to variations, either due to external factors (e.g., weather) or by the action of the network operator. This fundamental difference raises a variety of new issues to be addressed appropriately. We concentrated on conceiving reliable fixed broadband wireless networks under outage probability constraints , . We have developed a joint optimization of data routing and bandwidth assignment that minimizes the total renewal fees of licenses, while handling all the traffic requirements simultaneously. We have proposed a chance-constrained mathematical program taking into account unreliable channel conditions. This approach remains one of the main challenges of modern stochastic programming and it is still considered as very difficult and widely intractable. We have derived integer linear programming (ILP) counterparts for these chance-constrained programs and propose cutset-based valid inequalities to enhance the performance of ILP solvers. Computational results illustrate the price of reliability and present a comparative study on the performance of the different formulations. Moreover, we have been interested in potential energy savings in fixed broadband wireless networks by selectively turning off idle communication devices in low-demand scenarios , . We have proposed a mathematical formulation of the problem relying on a fixed-charge capacitated network design (FCCND) problem, which is very hard to optimize. We have derived from this modeling heuristic algorithms producing feasible solutions in a short time. This work was done in collaboration with the SME 3Roam, and partially developed within the scope of the joint project RAISOM (Réseaux de collecte IP sans fil optimisés).

We have addressed the problem of computing the transport capacity of Wireless Mesh Networks (WMNs) dedicated to Internet access . Routing and transmission scheduling have a major impact on the capacity provided to the clients. A cross-layer optimization of these problems allows the routing to take into account contentions due to radio interference. We have presented a generic Mixed Integer Linear Programing (MILP) addressing gateway placement, routing, and scheduling optimizations in a WMN. We have then derived new optimization models that can take into account a large variety of radio interference models, and QoS requirements on the routing. We also provide efficient resolution methods that deal with realistic size instances. It allows to work around the combinatoric of simultaneously achievable transmissions and point out a critical region in the network bounding the network achievable capacity. Based upon strong duality arguments, it is then possible to restrict the computation to a bounded area. It allows for computing solutions very efficiently on large networks. We have then extended our models to deal with the dynamic caracteristics of the network . We have proposed a new robust optimization model that considers traffic demand uncertainty, in order to compute an optimal robust routing and bandwidth allocation in WMNs. We have presented a linear program efficiently solved by column generation, and we have quantified the price of robustness, i.e. the additional cost to pay in order to obtain a feasible solution for the robust scheme.

We have additionally investigated on the feasibility of providing network connectivity to vehicles over a predefined trajectory (trains, metros, urban buses, etc.) . The communication between the vehicle and the infrastructure network is based only on WiFi technology. The contributions of this work are two-fold: 1) the horizontal handover (between WiFi access points) and 2) the design and analysis of an infrastructure network (backbone network plus WiFi access network) deployed along the trajectory of the vehicle.

We have studied algorithmic and complexity issues originating from the problem of data gathering in wireless networks
. We give an algorithm to construct minimum makespan
transmission schedules for data gathering when the communication graph is a tree network, the interference range is
*any*integer

Distributed or peer-to-peer storage solutions rely on the introduction of redundant data to be fault-tolerant and to achieve high reliability. To ensure long-term fault tolerance, the storage system must have a self-repair service that continuously reconstructs lost fragments of redundancy. The speed of this reconstruction process is crucial for the data survival. In , we propose a new analytical framework, based on queuing models, to estimate the repair time and the probability of data loss. This model takes into account the correlation of concurrent repairs. The models and schemes proposed are validated by mathematical analysis, extensive set of simulations, and experimentation using the Grid'5000 test-bed platform. Recently, the Regenerating Codes were proposed as an improvement over classical replication and erasure codes to introduce redundancy. These codes make a better use of the available bandwidth when reconstructing the missing information. In , we propose a new code based on a hybrid approach, Double Coding, and compare it to existing codes from the point of view of availability, durability and storage space.

Time-shifted streaming (or catch-up TV) allows viewers to watch their TV programs within an expanded time window. In , we emphasize the challenging characteristics of time-shifted TV systems that prevent known delivery systems to be used. We model time-shifted TV as multiple-interval graph, then we present a Peer-Assisted Catch-Up Streaming system, namely PACUS, where a set of end users' computers assists the server for the content delivery. We show in particular how the PACUS tracker server can be efficiently implemented for catch-up TV. We demonstrate the benefits of PACUS by simulations. We especially highlight that PACUS reduces the traffic at the server side with the advantages of lightweight and self-adaptive unstructured peer-to-peer systems.

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The works related to simulation and optimization tools address two kinds of issues: issues related to the development of the tools and their associated methodology, and issues related to the use of these tools in order to investigate a particular problem or assess the performances or properties of a particular system.

Since 2005,
Mascottehas been developing a discrete event simulation architecture, named OSA, whose aim is to investigate how new software engineering techniques,
such as component-based frameworks or Aspect Oriented Programming can help improving the simulation methodology, especially in terms of software reuse
,
,
. After six years of research development, OSA entered in the
process of being diffused in 2011. This process is supported by a two-year INRIA “Development Action” (ADT) funding. This first year was devoted to cleaning the code base and produce a public
release with a significant effort placed on user documentation and tutorial (cf
http://

Aside our efforts on the OSA project, we are strongly involved in the USS-SimGrid ANR funded project, whose aim is at developing an efficient simulation platform geared at Grid Computing and very large scale distributed computing architectures. In this project, we worked on two tasks:

Monitoring and characterization of the workload of large scale distributed applications ;

Support for modeling Peer-to-peer applications in the SimGrid simulator (originally designed for modeling grid-computing platforms).

We also pursued our involvement in the Discrete Event Systems Specification (DEVS) standardization effort , . This formalism has reached a strong agreement amongst the community, but it still lacks implementation standard. Since OSA is aimed at providing better support for methodology, we consider necessary to support DEVS and participate to this effort. Our particular focus was on techniques and Architecture Description Languages (ADLs) for describing very large models of distributed applications .

Regarding our works on simulation studies and application-oriented developments, this year was the conclusion of our effort on the Internet on Rails project . In this project, we studied and designed, both by means of simulations and experimentations, a low cost communication architecture based on IEEE 802.11 WiFi to provide high quality Internet access onboard high speed trains.

.

Mascotteprincipally investigates applications in telecommunications via Graph Theory (see other objectives). However it also studies a number of theoretical problems of general interest. Our research mainly focused on graph coloring and some other problems arising from networks problems.

Coloring and edge-coloring are two central concepts in Graph Theory. There are many important and long-standing conjectures in these areas. We are trying to make advances towards such conjectures, in particular Steinberg's conjecture, the List coloring Conjecture and the Acyclic Edge-Coloring Conjecture.

We are also interested in coloring problems arising from some practical problems: improper coloring,

We also study some other variants of coloring like non-repetitive coloring or frugal coloring.

For all the coloring problems, we also consider the associated algorithmic problem, which consists in designing algorithms for finding the minimum number of colors of a coloring of a given graph. Algorithmic results on graph coloring are presented in Section .

The most classical notion of coloring (of edges or vertices) is the one of proper coloring, in which we insist on two adjacent elements to have distinct colors. However, it is usual to
consider additional constraints,as well as relaxed constraints. For each variant of coloring, one can consider, its list version in which every element
* $L$-colorable*if is has an

The famous Four Color Theorem states that every planar graph can be properly colored with 4 colors and Thomassen Five Color Theorem states that the choosability of every planar graph is at most 5. Hence, a natural question is to ask about the chromatic number and choosability of graphs with few crossings. In , we disprove a conjecture of Oporowski and Zhao stating that every graph with crossing number at most 5 and clique number at most 5 is 5-colorable. However, we show that every graph with crossing number at most 4 and clique number at most 5 is 5-colorable. We also show some colorability results on graphs that can be made planar by removing few edges. In particular, we show that if there exists three edges whose removal leaves the graph planar then it is 5-colorable. In , we show that every graph with two crossings is 5-choosable. We also prove that every graph which can be made planar by removing one edge is 5-choosable.

Another famous theorem on planar graphs is the one of Grötzsch, which says that every planar graph with no cycle of length 3 can be properly 3-colored. Steinberg's Conjecture (1976)
asserts that a graph with no cycles of length 4 or 5 is 3-colorable. Many approaches have been used towards this conjecture. We considered the following one in which, we relax the
constraints on the color classes. Instead of insisting on them be independent sets, we allow them to induce a graph with some bounded degree. A graph
* $(i,j,k)$-colorable*if its vertex set can be partitioned into three sets

A classical constraint added to a proper coloring is that at least three colors appears on each cycle, in which case we speak about acyclic coloring. In other words, the graph induced by
the elements of any two color classes is a forest. The
*acyclic chromatic index*of a graph
*acyclic edge-coloring*with

Even stronger constraints are the following: a proper coloring of a graph is
*2-frugal*(resp.
*linear*) if the graph induced by the elements of any two color classes is of maximum degree 2 (resp. is a forest of paths). In
, we improve some bounds on the 2-frugal choosability and
linear choosability of graphs with small maximum average degree.

We studied several variants of vertex and edge colorings of plane graphs insisting one some constraints on the faces.

A face of a vertex colored plane graph is called
*loose*if the number of colors used on its vertices is at least three. The
*looseness*of a plane graph

A vertex coloring of a 2-connected plane graph
*strong parity vertex coloring*if for every face

A
*facial parity edge coloring*of a connected bridgeless plane graph is such an edge coloring in which no two face-adjacent edges (consecutive edges of a facial walk of some face)
receive the same color, in addition, for each face

A sequence
*repetition*. A sequence
*non-repetitive*if no
*block*(i.e. subsequence of consecutive terms of
*non-repetitive*if the sequence of colors of its edges is non-repetitive. If
*facial non-repetitive edge-coloring*of
*facial trail*(i.e. trail of consecutive edges on the boundary walk of a face) is non-repetitive. We denote

In
and
, we study a coloring problem motivated by a practical
frequency assignment problem and up to our best knowledge new. In wireless networks, a node interferes with the other nodes the level of interference depending on numerous parameters:
distance between the nodes, geographical topography, obstacles, etc. We model this with a weighted graph

Several on-line algorithms producing colorings have been designed. The most basic and most widespread one is the greedy algorithm. The largest number of colours that can be given by the
greedy algorithm on some graph. is called its
*Grundy number*. Determning the Grundy number of a graph is NP-hard even for

In
, we study a game version of greedy coloring. Given a graph

A
*wheel*is a graph formed by a chordless cycle and a vertex that has at least three neighbors in the cycle. We prove in
that every 3-connected graph that does not contain a wheel as a
subgraph is in fact minimally 3-connected. We prove that every graph that does not contain a wheel as a subgraph is 3-colorable. We were then told that this result was already proved by
Thomassen, though with a different proof.

Gallai-Hasse-Roy-Vitaver Theorem states that every

Matchings and independent sets are important substructures which appears in many problems. In particular, color classes of vertex-colorings and edge-colorings are independent sets and matchings, respectively.

In
, we show that every cubic bridgeless graph

Hypergraphs, also called set systems, are a natural generalization of graphs. In a graph an edge is set of two vertices, while in a hypergraph an edge is a set of any size. It turns out to
be an important notion in database theory. A digraph is

The first and second Zagreb indices of a graph are defined by

An
*induced
$H$-decomposition*of a graph

.

Mascotteis also interested in the algorithmic aspects of Graph Theory. In general we try to find the most efficient algorithms to solve various problems of Graph Theory and telecommunication networks.

Almost all graph coloring problems are NP-hard and most of them are even hard to approximate. Hence, to solve them efficiently, we aim at designing general exponential-time algorithms as well as polynomial-time algorithms for special classes. This is examplified by the following results.

An
* $L(p,q)$-labeling of
$G$*is an integer assignment

For some coloring problems that are known to be NP-hard for general graphs, we give some polynomial-time algorithms for the restriction to some graph classes. These graph classes defined
in terms of forbidden induced subgraphs. In
,
, we provide linear algorithms for coloring

We used graph theory to model various networks' problems. In general we study their complexity and then we investigate the structural properties of graphs that make these problems hard or easy. In particular, we try to find the most efficient algorithms to solve the problems, sometimes focusing on specific graph classes where the problems are polynomial-time solvable.

A subset

The geodesic convexity of graphs naturally extends the notion of convexity in euclidean metric spaces. A set

A circuit in a simple undirected graph

Pursuit-evasion encompasses a wide variety of combinatorial problems related to the capture of a fugitive residing in a network by a team of searchers. The goal consists in minimizing the number of searchers required to capture the fugitive in a network and in computing the corresponding capture strategy. This can also be viewed as cleaning the edges of a contaminated graph. We investigated several variants of these games.

Graph searching, where the fuggitive is arbitrary fast and moves simultaneously to the searchers, has been widely studied for its close relationship with graph decompositions. More recently, a variant of graph searching, namely the graph processing game, has been widely studied as a model for the routing reconfiguration in WDM networks (see Section ). In , we give a linear time (resp. polynomial-time) algorithm to recognize graphs (resp., digraphs) with process number at most 2, along with a characterization in terms of forbidden minors, and a structural description. In , we give a polynomial (both in terms of time complexity and in the number of exchanged messages) distributed algorithm to compute the process number of trees. By slightly modifying the intial parameter of the algorithm, it also allows to compute various parameters of trees as pathwidth, search number, etc.

The "Cops and Robber Games" are turn-by-turn games where a team of cops purchase a robber in a graph. We investigated two generalizations of the game introduced by Quilliot, Nowakoski and Winkler in 1983. We provided structural characterizations of graphs where one cop is sufficient to capture a fast fugitive able to hide . In particular, one of these characterizations relies on hyperbolicity of the considered graph.

A surprising application of "Cops and Robber"-like games is the problem for a web-browser to download documents in advance while an internaut is surfing on the Web. In , we provide a modelling of the prefetching problem in terms of Cops and Robber games. The parameter to be optimized is then the download-speed necessary for the Internaut only accesses to already download webpages. This allows us to provide several complexity results and polynomial-time algorithms in some graph classes.

We investigated algorithmic problems arising in complex networks like the Internet or social networks. In this kind of networks, problems are becoming harder or impracticable because of the size and the dynamicity of these networks. One way to handle the dynamicity is to provide (distributed) fault tolerant algorithms. Studying the mobile agents paradigm seems to be a promissing approach (somehow related to Cops and Robber in Section ) to adress some models of distributed computing. We considered self-stabilizing algoritms for the gathering problem, and algorithms for updating routing tables.

Besides, the more an algorithm uses local information, the easier it is to update/correct the behaviour of the algorithm. In this direction, we investigated communication problems through game theory. We also studied the power of a communication model using only localized information, i.e., we study what can be computed using this communication model.

We address dynamic large scale emerging networks, e.g., mobile sensor (agent) networks. The agents are resource limited and prone to failures. They move almost unpredictably and communicate in pairs. Population Protocol model is a communication model suited for such networks. We use a recently proposed version of this model where every agent is associated with a parameter called Cover Time. Cover Times abstract the interaction characteristics of mobile agents and allow the design of fast converging protocols and the evaluation of their convergence times (this is impossible in the original model). We take advantage of this model and perform first analytical analysis of a data collection protocol used in the ZebraNet project for the wild-life tracking of zebras. We propose alternative data collection protocols for ZebraNet and we analysis their time complexities , , . To achieve fault-tolerance in population protocols, we develop a generic self-stabilizing transformer . This is an automatic technique to convert a protocol to its self-stabilizing version.

In addition, we address important problems of coordination and synchronization. We present and prove correct two self-stabilizing deterministic protocols solving the classical mutual exclusion problem and the group mutual exclusion one .

Arc-Flags is a data structure used to speed-up the shortest paths computation in a graph. In , we introduce a new data structure, named Road-Signs, which allows us to efficiently update the Arc-Flags of a graph in a dynamic scenario. Road-Signs can be used to compute Arc-Flags, can be efficiently updated and do not require large space consumption for many real-world graphs.

Since, we need to face both locality and dynamicity issues, we are developing new techniques allowing to obtain global structural information from local (partial) views of the network.
In
,
, we has investigated the question of determining which graph
properties can or cannot be computed using only local information. We consider the following model: each of the

Mascotteis part of the join laboratory INRIA / Alcatel-Lucent Bell-labs France within the ADR HiMa (research action on High Manageability) and works on autonomous dynamic management of virtual topologies.

On Wireless IP Service Deployment optimization and monitoring.

"Convention de recherche encadrant une bourse CIFRE" on the topic
*Outils algorithmiques pour la détection des communautés*.

"Convention de recherche encadrant une bourse CIFRE" on the topic
*Smart Transports: optimisation du trafic dans les villes*.

The objectives of the project DIMAGREEN (DesIgn and MAnagement of GREEN networks with low power consumption) are to introduce and analyze energy-aware network designs and managements in order to increase the life-span of telecommunication hardware and to reduce the energy consumption together with the electricity bill.

(
http://

The project AGAPE (Parameterized and exact graph algorithms) is led by Mascotteand implies also LIRMM (Montpellier) and LIFO (Orléans). The aim of AGAPE is to develop new techniques to solve exactly NP- hard problems on graphs. To do so, we envisage two approaches which are closely related ways to reduce the combinatorial explosion of NP-hard problems: moderately exponential exact algorithms and fixed-parameter tractability.

(
http://

The ECOSCells (Efficient Cooperating Small Cells) project aims at developing the algorithms and solutions required to allow Small Cells Network (SCN) deployment. The consortium gathers industrial groups, together with 3 SMEs and 6 research institutes: Alcatel-Lucent Bell Labs(leader), Orange Labs, 3-ROAM, Sequans, Siradel, INRIA teams Maestro, Mascotteand Swing, Université d'Avignon et des Pays de Vaucluse, Laboratoire des Signaux et Systèmes / Supelec, LAAS and Eurecom.

(
http://

The USS-SimGrid project aims at Ultra Scalable Simulations with SimGrid. This tool is leader in the simulation of HPC settings, and the main goal of this project is to allow its use in the simulation of desktop grids and peer-to-peer settings.

*Réseaux de communications*, working group of GDR ASR, CNRS. (
http://

*Action Graphes*, working group of GDR IM, CNRS. (
http://

Title: EULER (Experimental UpdateLess Evolutive Routing)

Type: COOPERATION (ICT)

Challenge: Future Internet Experimental Facility and Experimentally-driven Research

Instrument: Specific Targeted Research Project (STREP)

Duration: October 2010 - September 2013

Coordinator: ALCATEL-LUCENT (Belgium)

Others partners: IBBT (Belgium), UPMC (France), UCL (Belgium), RACTI (Greece), CAT (Spain)

See also:
http://

Abstract: STREP EULER (Experimental UpdateLess Evolutive Routing) is part of FIRE (Future Internet Research and Experimentation) objective of FP7. It aims at finding new paradigms to design, develop, and validate experimentally a distributed and dynamic routing scheme suitable for the future Internet and its evolution. The STREP EULER gathers 7 partners: Alcatel-Lucent Bell (leader) (Antwerp, Belgique), IBBT (Ghent, Belgium), UCL (Louvain, Belgium), RACTI (Patras, Grece), UPC (Barcelona, Spain), UPMC (ComplexNetworks, Paris 6), INRIA (MASCOTTE, GANG, CEPAGE). MASCOTTE is the leader of WP3 on Topology Modelling and Routing scheme experimental analysis.

On Graph coloring: theoretical and algorithmic aspects.

"Défis algorithmiques dans les réseaux de communication". The purpose of the project is to exchange expertise between the discrete optimization group of RWTH Aachen University and the MASCOTTE team at INRIA Sophia-Antipolis and to address algorithmic problems in communication networks.

Title: Web-Service approaches for simulation

INRIA principal investigator: Olivier Dalle

International Partner:

Institution: Carleton University (Canada)

Laboratory: Advanced Real-Time Simulation Laboratory

Duration: 2011 - 2014

See also:
http://

This Franco-Canadian team will advance research on the definition of new algorithms and techniques for component-based simulation using a web-services based approach. On the one hand, the use of web-services is expected to solve the critical issues that pave the way toward the simulation of systems of unprecedented complexity, especially (but not exclusively) in the studies involving large networks such as Peer-to-peer networks. Web-Service-oriented approaches have numerous advantages, such as allowing the reuse of existing simulators, allowing non-computer experts to merge their respective knowledge, or seamless integration of complementary services (eg. on-line storage and repositories, weather forecast, traffic, etc.). One important expected outcome of such approaches is to improve significantly the simulation methodology in network studies, especially by enforcing the seamless reproducibility and traceability of simulation results. On the other hand, a net-centric approach of simulation based on web-services comes at the cost of added complexity and incurs new practices, both at the technical and methodological levels. The results of this common research will be integrated into the discrete-event distributed simulators of both teams: the CD++ simulator at Carleton University and the simulation middle-ware developed in the MASCOTTE EPI, called OSA, whose developments are supported by an INRIA ADT since January 2011.

Title: Efficient algorithms in WIreless Networks

INRIA principal investigator: Frédéric Havet

International Partner:

Institution: Universidade Federal do Ceara (Brazil)

Laboratory: Laboratorio de Inteligencia Artificial

Duration: 2009 - 2011

See also:
http://

The research themes are the design of exact or approximate algorithms for solving problems in networks, in particular wireless networks. The problems that we will consider can be modelled as graph coloring or graph decomposition problems. More specifically, we studied the following problems: channel assignment in radio networks which can be modelled by various graph coloring problems, dynamic routing in wireless networks using microwave links, and routing reconfiguration in MPLS or WDM networks, certain models of which are closely related to graph searching problems and tree and path decompositions.

GRATEL (Graphs and Telecomunications) has been started in collaboration with LABRI Bordeaux, UJF Grenoble and three partners in Taiwan: Sun Yat-sen University, the National Taiwan University and Academia Sinica.

Collaboration and joint publications with B. Jaumard (Concordia), B. Reed (Mac Gill).

Visits of J. Yu and J. Peters (SFU Vancouver, Canada) in Mascotte and joint publications.

Reciprocal visits of N. Nisse in Chile and I. Rapaport (Universidad de Chile) and K. Suchan (Universidad Adolfo Ibáñez) in Mascotte. Moreover, there are joint publications.

Visits of J. Bang-Jensen (University of Southern Denmark). N. Nepomuceno (former PhD in Mascotte) went to University of Southern Denmark for his Post-Doc. Moreover, there are joint publications.

Long-term collaboration with University of Patras, D. Coudert spent 3 months there in 2011, joint participation in many european projects.

Visits of L. Gargano and U. Vaccaro (University of Salerno) and joint publications.

University of Southern Denmark, Odensee, Denmark, October 10-October 30, 2011 (3 weeks).

Universidade Federal do Ceara, Fortaleza, Brazil, November 28 - december 4 (1 week).

Lehrstuhl II fur Mathematik, RWTH Aachen - Aachen, Germany, September 11-16, 2011 (1 week) and December 12-16 (1 week).

National Sun Yat-Sen University, Kiaoshung, Taiwan, November 25 - December 2 (1 week).

University of l'Aquila, Italy, June 18 - July 9 (3 weeks).

University of Bergen, Bergen, Norway, April 4- April 30, 2011 (1 month) and November 16-18 (Colloquium Morgenstern).

Dipartimento di Informatica ed Applicazioni “Renato M. Capocelli” of the Università di Salerno, Salerno, Italy, July 15- August 31 (1 month 1/2).

University of West Bohemia, Pilsen, Czech Republic, November 28 - December, 4 (1 week).

Lehrstuhl II fur Mathematik, RWTH Aachen - Aachen, Germany, September 11-16, 2011 (1 week).

Charles University, Prague, Czech Republic, October 17-21, 2011 (1 week);

Lehrstuhl II fur Mathematik, RWTH Aachen - Aachen, Germany, September 11-16, 2011 (1 week) and December 12-16 (1 week).

SFU Vancouver, Canada, May 14 - June, 4 (3 weeks).

Universidad de Chile, Santiago, Chile, May, 2011 (2 weeks).

G-SCOP, Grenoble, October 19-21, 2011 (3 days).

Universidad Adolfo Ibáñez, Santiago, Chile, September 21 - December 28, 2011 (3 months).

University of Oran, Algeria, November 7-25, 2011 (3 weeks).

Dipartimento di Informatica ed Applicazioni “Renato M. Capocelli” of the Università di Salerno, Salerno, Italy, July 15- August 31 (1 month 1/2).

Carleton University, Ottawa, Canada, January 19-24 (1 week) and June 13 - July 8 (3 weeks).

Abbotsford and SFU, Vancouver, Canada, March 1st - April 15, 2011 (1 month 1/2).

Visit to Federal University of Ceará, Fortaleza, Brazil (December 22th, 2010 - January 15th, 2011).

Visit to Montpellier March 30-31.

Visit to LRI, University Paris-Sud 11, Orsay, France, (January 31-February 3, 2011).

Visit to University of Bergen, Norway (February 12-27, 2011); Visit the National Taiwan University, Taipei, Taiwan (March 9–16, 2011).

Visit the Research Unit 1 (RU1) of the Research Academic Computer Technology Institute (RACTI), Patras, Greece (January 8 till March 31, 2011); Visit the mathematics department of the National and Kapodistrian University of Athens, Greece (February 23-25, 2011); Visit the mathematics departement of RWTH Aachen, Germany (October 30 till November 4, 2011).

Visit to Carleton University, Ottawa, Canada (July 5 - August 3 2011).

Visit University of L'Aquila, L'Aquila, Italy (November 5-14 and December 12-15); Visit "Sapienza" University of Rome, Rome, Italy (November 8).

National Taiwan University, Taipei, Taiwan (March 9-12 and 17-18, 2011); National Sun Yat Sen University, Kiaoshung, Taiwan (March 13-16); Federal University of Ceara, Fortaleza, Brasil (April 4-8, 2011 and September 27-October 4, 2011); LIRMM, University Montpellier 2, (February 7-11, 2011 and October 14-15, 2011); LIFO, University of Orléans, (May 18-22, 2011); Lebanese University, Beyruth, Lebanon (May 16-20, 2011).

Visit RWTH Aachen University, Germany (December 5-9, 2011).

Visit to Louvain-la-Neuve University, Belgium, (July 8, 2011).

Visit to Carleton University, Ottawa, Canada (September 5-October 4-2011).

Visit to Carleton University, Ottawa, Canada (August 7-September 4 2011).

Visit to Universidad de Chile, Santiago, Chile, (2 weeks, January 13-31, 2011); Visit to CITI, Lyon, France, (1 week, July 25-29, 2011).

Visit RWTH Aachen University, Germany (July 4-15, 2011 and December 5-9, 2011);

supervised the internship of Guillaume Ducoffe (École Polytechnique Universitaire Nice Sophia Antipolis) on Eulerian and Hamiltonian hypergraphs, June 15- August 31 (2 months 1/2).

supervised the internship of Felipe Menezes Machado (Universidade Federal de Minas Gerais, Belo Horizonte, Brasil) on studying community structures in dynamic graphs, April-June 2011 (3 months 1/2).

supervised the internship of Truong Khoa Phan (parcours UBINET master IFI, UNS, France) on Minimization of network power consumption with WAN Optimization, March-August 2011 (6 months).

supervised the internship of Dang Dinh Khanh (parcours UBINET master IFI, UNS, France) on the study of variants of Cops and Robber Games, March-August 2011 (5 months 1/2).

ALERTE (ALgorithmes Efficaces pour les Réseaux de TElécommunications), with Pargo Team, Universidade Federal do Ceará, Brazil, accepted in June 2011.

PhD Grant of J.-C. Maureira supervised by J.-C. Bermond and O. Dalle.

Expert for DRTT, and various projects outside France (Canada, Qatar,...); Responsible of the
*Pôle ComRed*of I3S till January 31th; Member of the Ph.D. committee of the University of Marseille; Member of the
*comité de sélection des ATER*till march 15; Member of the I3S laboratory committee (until October).

Member of the
*comité du suivi doctoral*of INRIA Sophia Antipolis (since January 2009); Member of INRIA working group GT AER; Member of
*comité de sélection 27e section*of UNS, 2011; Member of the scientific board of the GIS ENSL-UNS (CNRS, ENSL, INRIA, UNS) since 2011; Expert for the National Sciences and
Engineering Research Council of Canada (NSERC), the Future and Emerging Technologies Open Scheme (FET-Open) European program, and the ANR (ARPEGE, JC-JC, SIMI).

Member of the
*comité de sélection 27e section*of UNS; Member of the CUMIR comittee of INRIA Sophia Antipolis; Expert reviewer for Ministry of Higher Education and Research (MESR) CIR applications
(Credit Impot Recherche); Member of the PhD defense committee of P. Vehlo, Univ. Grenoble, July 2011 (reviewer).

Expert for ANR (
*Agence Nationale de la Recherche*) and its analogue in Slovakia VEGA; Member of the I3S laboratory committee (until October); External member of the Doctoral Deparment I2S committee
(Montpellier); Reviewer of the PhD Theses of V. Campos (Federal University of Ceara, Brasil, September 2011) and S. Ghazal (Lebanese University, Lebanon and University of Lyon I, December
2011); Examiner of the PhD Thesis of Anthony Perez (University of Montpellier 2, November 2011).

Member of the
*comité de sélection 27e section*of Université de Montpellier II; Member of the CDL (Commission for software development) at INRIA Sophia Antipolis since 2009; Member of the
*Conseil de Département*(Department Committee) of IUT Nice since 2007; Responsible of the International stream Ubinet, Master IFI (
http://

Member of the
*comité de sélection 27e section*of Université de la Méditerranée; member of the
*comité de sélection 27e section*of Université de Montpellier II, 2011; co-responsible of the Computer Science course of MPSI, INRIA-Lycée International de Valbonne.

Expert for DRTT PACA; Member of
*comité de sélection 27e section*of UNS, 2011 (ATER, "ad-hoc"); Member of DCCE committee ED STIC; Member of the PhD defense committee of Swann Perarnau (University of Grenoble,
December 1st 2011).

Combinatorics Probability and Computing, Computer Science Reviews, Discrete Mathematics, Discrete Applied Mathematics, Journal of Graph Theory, Journal Of Interconnection Networks (Advisory Board), Mathématiques et Sciences Humaines, Networks, Parallel Processing Letters the SIAM book series on Discrete Mathematics, Transactions on Network Optimization and Control , Discrete Mathematics, Algorithms and Applications.

Discrete Applied Mathematics.

Discrete Mathematics and Theoretical Computer Science.

Pôle ResCom du GDR ASR du CNRS (since 2005); Rencontres francophones sur les aspects algorithmiques des télécommunications (AlgoTel).

*ICST Intl. Conf. on Simualtion Tools and Techniques*(SIMUTools).

*Journées Combinatoire et Algorithmes du Littoral Méditerranéen*(JCALM);
*Journées Graphes et Algorithmes*(JGA); GT Graphes du GDR IM du CNRS.

13mes rencontres francophones sur les Aspects Algorithmiques des Télécommunications, Agay, France, May 2011; Organizing Chairs: F. Giroire and N. Nisse.

25th ACM/IEEE/SCS Workshop on Principles of Advanced and Distributed Simulation (PADS 2011), Nice, France (June 14-17, 2011). Organized: by O. Dalle, A. Lancin, E. Mancini and I. Tahiri.

Workshop Cycles and colorings 2011, Nový Smokovec, Slovakia, September 04-09, 2011. Member of the organizing commitee: F. Kardoš.

13th Workshop on Advances in Parallel and Distributed Computational Models (APDCM2011), Anchorage, Alaska, USA (May 16, 2011).

10th International Symposium on Experimental Algorithms (SEA'11), Chania, Greece (May 5-7, 2011); 13es Rencontres Francophones sur les Aspects Algorithmiques des Télécommunications (AlgoTel'11), Cap Estérel, France (May 23-26, 2011); 18th International Symposium on Fundamentals of Computation Theory (FCT), Oslo, Norway (August 22-25, 2011).

Member of International Workshop on SImulation Models and Techniques for Intelligent Mobility (SIMTIM −2011), 2nd International Track on Collaborative Modeling & Simulation - CoMetS’11, DEVS/TMS 2011, Boston, MA, April 2011, Omnet++ Workshop, Barcelona, March 2011.

Journées Graphes et Algorithmes, Lyon, France, (November 16-18, 2011).

Workshop TERA-NET’11, Toward Evolutive Routing Algorithms for scale-free/internet-like NETworks, Roma, September 19, 2011.

Seminar at the MPLA graduate students seminar, University of Athens, Greece (February 25, 2011); Seminar at mathematics department of RWTH Aachen, Germany (November 2, 2011).

46th Czech-Slovak Conference on Graph Theory, Banská Bystrica, Slovakia (June 06-10, 2011). 43th Slovak Mathematicians Conference, Jasná, Slovakia (December 01-04, 2011).

IMSA Workshop on Algorithms and Randomness, Santiago, Chili, February 2011.

AGAPE meeting, Montpellier, (February 7-9, 2011). Attended by J. Araújo, A. K. Maia, F. Havet, R. Pardo Soares, S. Pérennes, L. Sampaio (Speaker) and I. Tahiri.

*Évaluation du pôle COMRED*, Sophia Antipolis, France (January 19th, 2011). Attended by most of the Mascotte members (speaker: J. Moulierac).

Scientific meeting of ANR Verso ECOSCELLS, Villarceaux, France (June 9, 2011). Attended by D. Coudert.

Roma, September 20-21, 2011. Attended by A. Lancin, B. Li and N. Nisse.

Interim meeting of the FP7 STREP EULER project, Paris, France (January 20-21, 2011). Attended by D. Coudert and A. Lancin.

Retreat of the FP7 STREP EULER project, St-Raphael, France (May 10-12, 2011). Attended by D. Coudert and A. Lancin.

Annual meeting of FP7 STREP EULER project, Barcelona, Spain (November 7-9, 2011). Attended by D. Coudert and A. Lancin.

FIRE Conference co-located with the Future Internet Week, Poznan, Poland (October 26-27, 2011). Attended by D. Coudert.

Mid-term Workshop, Taipei (March 11-12, 2011). Attended by N. Cohen (speaker) and F. Havet (speaker).

GreenDays meeting, Paris, (May 31th - June 1st, 2011). Attended by Y. Liu.

8th day on Network Optimization, Paris, France (October 21, 2011). Attended by C. Caillouet.

Paris VI, Paris, France (19-21 January 2011). Attended by N. Cohen.

Mascotte project annual seminar, Agay, France (May 26-27, 2011). Attended by most of the MASCOTTE members.

Journée du pôle MDSC de l'I3S, Sophia Antipolis (May 23, 2011). Attended by F. Havet.

10th
*Journées du Pôle ResCom du GDR ASR*, Paris, France (October 20-21, 2011). Attended by D. Coudert.

LEA STRUCO Kick-off meeting, Paris, (December 8-9, 2011). Attended by F. Havet and F. Kardoš.

Meeting, Nice, France (Janaury 22, 2011). Organized by O. Dalle, E. Mancini and J. Ribault.

Fourth International Conference on Combinatorics, Graph Theory, and Applications, Elgersburg, Germany (March 21-25, 2011). Attended by F. Kardoš (speaker).

10th International Conference on Ad Hoc Networks and Wireless, Paderborn, Germany (July 18-20, 2011). Attended by C. Caillouet (speaker).

13mes rencontres francophones sur les Aspects Algorithmiques des Télécommunications, Agay, France, May 23-26, 2011. Attended by J. Araújo, J.-C. Bermond, J. Burman (speaker), C. Caillouet (speaker), D. Coudert, F. Giroire, D. Mazauric (speaker), J. Moulierac, N. Nisse, L. Sampaio, R. Pardo Soares and I. Tahiri (speaker).

Workshop DEVS/TMS, colocated with the SpringSim 2011 Conference, Boston, MA, April 2011. Attended by O. Dalle (speaker).

DIPAM Workshop on Combinatorics and Graph Theory, Warwick, Great Britain (April 04-07, 2011). Attended by F. Kardoš (speaker).

25th International Symposium on DIStributed Computing, Roma, September 20-22, 2011. Attended by A. Lancin and B. Li.

European Conference on Combinatorics, Graph Theory and Applications, Budapest, Hungary (August 29th - September 2nd, 2011). Attended by J. Araújo (speaker), L. Sampaio and R. Pardo Soares.

4th Workshop on GRAph Searching, Theory and Applications, Dagstuhl, Germany, February 14-18, 2011. Attended by N. Nisse (speaker).

Workshop on Algorithms and Randomness, Santiago, Chile, January 18th, 2011. Attended by N. Nisse (speaker).

5th International Network Optimization Conference, Hamburg, Germany (June 13-16, 201). Attended by I. Tahiri.

International Workshop on Combinatorial Algorithms, Victoria, Canda (June 20th - June 22th, 2011). Attended by J. Araújo (speaker).

13èmes Journées Graphes et Algorithmes, Univ. Claude Bernard, Lyon, France, November 16-18, 2011. Attended by J. Araújo (speaker), F. Havet, F. Kardoš, A. K. Maia (speaker), G. Morel, N. Nisse (speaker) and L. Sampaio (speaker).

La 7ème édition des Journées Polyèdres et Optimisation, Valenciennes, France (8-10 june 2011). Attended by I. Tahiri.

6th Latin-american Algorithms, Graphs and Optimization Symposium, Bariloche, Argentina (March 28 - April 1, 2011). Attended by F. Havet (speaker) and A. K. Maia (speaker).

12ème congrès annuel de la Société française de Recherche Opérationnelle et d'Aide à la décision, Saint-Etienne, France (March 2nd - 4th, 2011). Attended by G. Morel.

Workshop Toward Evolutive Routing Algorithms for scale-free/internet-like NETworks, Roma, September 19, 2011. Attended by D. Coudert, A. Lancin, B. Li and N. Nisse.

Workshop on distributed storage systems, Cesson Sévigné, France (September 19th - September 20th, 2011). Attended by J. Araújo and R. Modrzejewski (speaker).

WinterSim Conference 2011, Phoenix, AZ, USA (December 11-14, 2011). Attended by E. Mancini.

9èmes Journées Combinatoire et Algorithmes du Littoral Méditerranéen, Marseille,(February 18, 2011). Attended by J. Araújo, R. Pardo Soares and F. Havet.

10èmes Journées Combinatoire et Algorithmes du Littoral Méditerranéen, Barcelona, Spain, (June 7-8, 2011). Attended by J.Araújo, N. Cohen, D. Coudert, F. Havet, N. Nisse and L. Sampaio.

Summer school on Networking, Louvain-la-Neuve, Belgium, (July 6-7, 2011). Attended by A. Lancin.

L'école de la 7ème édition des Journées Polyèdres et Optimisation, Valenciennes, France (6-8 june 2011). Attended by I. Tahiri.

Geilo, Norway (23-25 February 2011). Attended by N. Cohen (speaker).

Ecole de Recherche Operationnelle, Université d'Abomey-Calavi(UAC)/Institut des Mathematiques et Sciences Physiques(IMSP), Porto-Novo, Benin, November, 14-19 2011. Attended by A. Kodjo and M. Toko-Worou.

Laboratoire de Mathématiques d'Orsay (Université Paris-Sud 11), Orsay, France (17-19 January 2011). Attended by N. Cohen (speaker).

Winter School on Network Optimization, Estoril, Portugal (January 17-21, 2011). Attended by C. Caillouet.

Since April 1, J.-C. Bermond is in charge of the attractiveness of the center INRIA Sophia Antipolis Méditerannée.

J.-C. Bermond gave a talk at the Colloquium organized in Montpellier on March 31, 2011.

J.-C. Bermond gave a talk at the Colloquium organized in Sophia Antipolis on May 12, 2011.

D. Mazauric gave a talk to the students of Polytech' Nice, on "Compromis pour le problème du reroutage dans les réseaux optiques" at Sophia Antipolis (March 10, 2011).

F. Havet presented the stand "Mathématiques" at Rians, France (October 12-16, 2011).

F. Havet presented "Maths et magie", Rians, France (February 12, 2011).

F. Havet gave two conferences "Graph theory and networks” and “Researcher as a job” in Lycée du Rempart, Marseille, November 24, 2011.

D. Mazauric gave a talk to the students of SUP'COM, on "Reconfiguration du routage dans les réseaux optiques" at Sophia Antipolis (July 12, 2011).

**Licence:**

- ASR5 - Networks, 150h, Level L1, IUT Nice Côte d'Azur, University of Nice Sophia Antipolis.

- Introduction to Operating Systems, 40h, Level L1, IUT Nice Côte d'Azur, University of Nice Sophia Antipolis.

- Informatique, 20h, Level L1 (classe préparatoire MPSI), Lycée International de Valbonne.

- IT Tools, 32h, Level L1, IUT Nice Côte d’Azur, University of Nice Sophia Antipolis.

- Programmation fonctionnelle (Scheme), 18h, Level L1, UFR Sciences, University of Nice Sophia Antipolis.

- Database and advanced information system, 36h, Level L2, IUT Nice Côte d’Azur, University of Nice Sophia Antipolis.

- Operating Systems : Advanced Programming, 63h, Level L2, IUT Nice Côte d'Azur, University of Nice Sophia Antipolis.

- Algorithmique et Programmation, 35h, Cycle Initial Polytechnique 2, École Polytech'Nice, University of Nice Sophia Antipolis.

- Mathématiques discrètes, 64h, Level L3, Ecole Polytech'Nice, University of Nice Sophia Antipolis.

- Advanced Networks, 15h, Level L3, IUT Nice Côte d'Azur, University of Nice Sophia Antipolis.

- Object-Oriented Programming, 54h, L3, Licence Miage, Université de Nice, France.

- Graph Theory, 18h, Level L3, Mathematics Department, RWTH Aachen, Germany.

- Introduction to Algorithms, 36h, Level L3, IUT Nice Côte d'Azur, University of Nice Sophia Antipolis.

- Bash Scripting, 15h, Level L3, IUT Nice Côte d'Azur, University of Nice Sophia Antipolis.

- Linux Systems Administration, 24h, Level L3, IUT Nice Côte d'Azur, University of Nice Sophia Antipolis.

- Algorithmique et complexité, 25h, Level L3, IUT Nice Côte d'Azur, University of Nice Sophia Antipolis.

**Master:**

- Théorie des graphes, 24h, M1 PENSUNS, University of Nice Sophia Antipolis.

- Combinatoire des graphes, 25h, Level M2, Master MDFI, Université de la Méditerranée - Faculté des sciences de Luminy.

- Probabilistoc method, 18h, Master 2 Mathematics, Lebanese University, Beyruth, Lebanon.

- Algorithms for telecommunications, 42h, Level M2, Master IFI (international stream Ubinet), University of Nice Sophia Antipolis.

N. Nisse is co-responsible of the Computer Science course of MPSI.

M. Syska is responsible of the Computer Science Department of IUT since september 2011.

J.-C. Bermond is member of the scientific committee.

J. Moulierac was responsible of the International stream Ubinet, Master IFI (
http://

F. Giroire is responsible of the Internships within international stream Ubinet, Master IFI (
http://

J.-C. Bermond is member of the scientific committee of the international track of the M1.

**PhD:**

Nathann Cohen,
*Three years of graphs and music: some results in graph theory and its applications*, Université de Nice Sophia Antipolis, October 20, 2011, F. Havet.

J.-C. Maureira,
*Internet on rails*, Université de Nice Sophia Antipolis, January 21, 2011, J.-C. Bermond and O. Dalle.

D. Mazauric,
*Optimisation discrète dans les réseaux de télécommunication: reconfiguration du routage, routage efficace en énergie, ordonnancement de liens et placement de données*, Université de
Nice Sophia Antipolis, November 7, 2011, P. Nain and J.-C. Bermond.

J. Ribault,
*Reuse and Scalability in Modeling and Simulation Software Engineering*, Université de Nice Sophia Antipolis, January 20, 2011, O. Dalle.

* *

**PhD in progress:**

*3rd year:*

J. Araújo,
*Dynamic network routing*, since December 2009, J.-C. Bermond, C. Linhares Sales and F. Giroire.

L. Sampaio,
*Algorithmic aspects of graph colorings*, since November 2009, F. Havet.

I. Tahiri,
*Optimisation dans les réseaux de collecte IP sans fils*, since November 2009, D. Coudert.

M. Toko Worou,
*Outils algorithmiques pour la détection des communautés*, since November 2009, J.-C. Bermond and J. Galtier.

* *

*2nd year:*

S. Félix,
*Smart transports : optimisation du trafic dans les villes*, since January 2011, J.-C. Bermond and J. Galtier.

A. Lancin,
*Study of network properties for efficient routing algorithms*, since January 2011, D. Coudert.

R. Modrzejewski,
*Systèmes pair-à-pair de partage de données*, since November 2010, S. Pérennes and F. Giroire.

R. Pardo Soares,
*Routing reconfiguration in WDM networks*, since November 2010, D. Coudert and N. Nisse.

* *

*1st year:*

A. Kodjo,
*Design and optimization of multi-operators wireless backhaul networks*, since October 2011, D. Coudert.

B. Li,
*Study of Internet model and its properties for efficient routing algorithms*, since October 2011, D. Coudert and N. Nisse.

A. K. Maia,
*Partitions of directed graphs*, since September 2011, F. Havet.

T. K. Phan,
*Design and Management of networks with low-power Consumption*, since October 2011, D. Coudert and J. Moulierac.