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

The objectives of the Coati project-team are to design networks and communication algorithms. In order to meet these objectives, the team studies various theoretical problems in Discrete Mathematics, Graph Theory, and Algorithmics and develops applied techniques and tools, especially for Combinatorial Optimization and Computer Simulation. In particular, Coati (previously Mascotte) used 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 software such as Grph and DRMSim, and in the contribution to large open source software such as SageMath.

Members of Coati have a good expertise in the design and management of wired and wireless backbone, backhaul, broadband, and complex networks. On the one hand, we cope with specific problems such as energy efficiency in backhaul and backbone networks, routing reconfiguration in connection oriented networks (MPLS, WDM), traffic agregation in SONET networks, compact routing in large-scale networks, survivability to single and multiple failures, etc. These specific problems often come from questions of our industrial partners. On the other hand, we study fondamental problems mainly related to routing and reliability that appear in many networks (not restricted to our main fields of applications) and that have been widely studied in the past. However, previous solutions do not take into account the constraints of current networks/traffic such as their huge size and their dynamics. Coati thus puts a significant research effort in the following directions:

**Energy efficiency** at both the design and management levels. More
precisely, we plan to develop accurate modeling of the power consumption of
various parts and components of the networks through measurement done in
collaboration with industrial partners (Alcatel-Lucent, 3Roam, Orange labs,
etc.). Then, we shall propose new designs of the networks and new
routing algorithms in order to lower the power consumption.

**Larger networks:** Another challenge one has to face is the
increase in size of practical instances. It is
already difficult, if not impossible, to solve practical instances optimally
using existing tools. Therefore, we will have to find new ways to solve
problems using reduction and decomposition methods, characterization of
polynomial instances (which are surprisingly often the practical ones), or
algorithms with acceptable practical performances.

**Stochastic behaviors:** Larger topologies mean frequent changes due
to traffic and radio fluctuations, failures, maintenance
operations, growth, routing policy changes, etc. We aim at including these
stochastic behaviors in our combinatorial optimization process to handle the
dynamics of the system and to obtain robust designs of networks.

Coati is mostly interested in telecommunications networks. Within this domain, we consider applications that follow the needs and interests of our industrial partners, in particular Orange Labs or Alcatel-Lucent Bell-Labs, but also SMEs like 3-Roam and Avisto.

We focus on the design and management of heterogeneous networks. The project has kept working on the design of backbone networks (optical networks, radio networks, IP networks). We also study routing algorithms such as dynamic and compact routing schemes in the context of the FP7 EULER leaded by Alcatel-Lucent Bell-Labs (Belgium), and the evolution of the routing in case of any kind of topological modifications (maintenance operations, failures, capacity variations, etc.).

Our combinatorial tools may be well applied to solve many other problems in various areas (transport, biology, resource allocation, chemistry, smart-grids, speleology, etc.) and we intend to collaborate with teams of these other domains.

For instance, we have recently started a collaboration in Structural Biology with EPI ABS (Algorithms Biology Structure) from Sophia Antipolis (described in Section ). Furthermore, we are also working on robot moving problems coming from Artificial Intelligence/Robotic with Xavier Defago (Associate Professor at Japan Advanded Institute of Science and Technology, Japan).

Around 20,000 lines of code, developed in Java, and licensed under LGPL.
See http://

The objective of Grph is to provide researchers and engineers a suitable graph library for graph algorithms experimentation and network simulation. Grph is primarily 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 Grph library. It allows manipulating large graphs (millions of nodes). Its model considers mixed graphs composed of directed and undirected simple- and hyper-edges. Grph comes with a collection of graph algorithms which is regularly augmented.

Grph includes bridges to other graph libraries such as JUNG, JGraphT, CORESE (a software developed by the WIMMICS team Inria-I3S), LAD (Christine Solnon, LIRIS), Nauty (Brendan D. McKay), SageMath, as well as specific algorithms developed by Matthieu Latapy and Jean-Loup Guillaume (LIP6), etc.

In 2013, we have added several graph algorithms to Grph (e.g., subgraph isomorphism, subgraph search as sets or regular expressions, transitive closure, etc.). In particular, a significant effort has been put on the support for paths with multiple data-structures for more efficient in-memory representation of paths, and the implementation of algorithms for the enumeration of paths, the characterization of paths, the computation of the k-shortest paths, etc. Furthermore, we have improved the support of weigths in graphs and developed software bridges to SageMath and OGDF. We have also added several models (link-failures, node mobility) for graph dynamics using the discrete-event simulator included in Grph, as well as models for the development of decentralized algorithms (useful for instance for the simulation of routing schemes). Finally, we have redesigned the website which now includes a forum gathering the community of users.

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) and its source code, developed in Python, Cython, and C++, has reached 350 MB.

It is of interest for Coati members because it combines a large collection of graph algorithms with various libraries in algebra, calculus, combinatorics, linear programming, statistics, etc. We use SageMath for quickly testing algorithms, analyzing graphs, and disseminating algorithms. We also use it for teaching purposes in the Master 2 IFI, stream UBINET.

In 2013, David Coudert has contributed to the development of the SageMath releases 5.0 to 6.0 with 10 patches (from bug fix to advanced graph algorithms) and participated to the reviewing process of more than 20 patches that are now part of the standard distribution.

Around 45,000 lines, developed in Java, collaboration between Coati, LaBRI, and Alcatel-Lucent Bell labs.

DRMSim relies on a discrete-event simulation engine aiming at enabling the large-scale simulations of routing models. DRMSim is developped in the framework of the FP7 EULER project. 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 a previously defined routing protocol and lightweight versions of BGP (Border Gateway Protocol).

The metric model takes measures along a discrete-event simulation which can be performed in many ways.

Commonly, a simulation campaign consists in iterating over the set of combinations of parameter values, calling the simulation function for every combination. These combinations are most often complex, impeding their description by a set of mathematical functions. Thus DRMSim provides a simulation methodology that describes (programmatically) the way a simulation campaign should be conducted.

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 Grph library.

DRMSim relies on the Mascsim abstract discrete-event simulation framework, the Grph library and the Java4Unix integration framework.

In 2013, the work on DRMSim consisted (1) in the implementation of a full support for dynamic networks, including topological modifications and evolving transfer loads in the simulated network. The implementation of the BGP protocol was updated so as to support these dynamic properties. (2) This implementation of BGP was also augmented with a framework enabling its dynamic profiling. (3) Finally DRMSim does no longer relies on the Dipergrafs library. Instead it now uses Grph, which brings better performance, stability and a broader set of graph algorithms.

See also the web page http://

Around 12,000 lines, developed in Python.

P2PVSim is a 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. And in 2012, a distributed version of P2PVSim was developed running on an arbitrary number of computers. It has been so far used with success on a dozen computers with multiple cores all located in the same LAN.

About 500 lines, developed in Java.

Papareto is a Java framework for the development of evolutionary solutions to computational problems. The primary motivation for developing an evolutionary framework was to give the Grph library the ability to generate particular graph instances. Papareto differs from other evolutionary frameworks (ECJ, WatchMaker, JGAP, etc) in the following ways:

it is *multi-objective*;

it is *not a genetic algorithms (GAs)* framework because it manipulates objects *as is*. It does not consider their chromosomes representation. Performance consequently is no longer impacted by the computational cost of encoding/decoding;

it *parallelizes* the creation and the evaluation of a new generation, adaptively to the evolving load of the computer;

it is *self-adaptive* in the sense that it dynamically evaluates the performance of the crossover and mutation operators, then gives greater priority to most efficient ones;

it is *easy to use*, by exposing the cleanest and more natural API possible and the minimal set of functionality enabling researchers and engineers to perform evolutionary computing;

See also the webpage
http://

Around 3,000 lines, developed in Java.

Toools is a general purpose Java toolbox which, much like Google Guava and Apache Commons, aims at providing classes useful in daily programming tasks. It focuses on the following topics:

runtime (threads, control of parallel executions of SIMD code, execution of external processes, management of I/O operations, piping);

input/output files (a complete, easier to use and more complete new model for files on disk is provided) and streams;

reflection, including dynamic loading of classes, classpath management, Java beans, and access to the source code at runtime;

application configuration files (parsing, querying, saving);

plain text, XML;

collections, including Java collection utilities and efficient sets of primitive integers;

mathematical and statistical operations.

See also the webpage http://

We ensure the maintenance of various tools developped in the past:

a software glue for the integration of Java applications intro the UNIX environment; http://

a Java toolkit for linear optimization; http://

a minimal middleware infrastructure for practical distributed computing; see http://

a discrete event simulation engine use in the DRMSim routing model simulator; http://

a Java toolkit for the XML (de)serialization of Java objects; http://

The notion of Shared Risk Link Groups (SRLG) has been introduced to capture survivability issues where some links of a network fail simultaneously. In this context, the diverse routing problem is to find a set of pairwise SRLG-disjoint paths between a given pair of end nodes of the network. This problem has been proved NP-complete in general and some polynomial instances have been characterized.

In , , we investigate the diverse-routing problem in networks where the SRLGs are localized and satisfy the *star property*. This property states that a link may be subject to several SRLGs, but all links subject to a given SRLG are incident to a common node. We first provide counterexamples to the polynomial-time algorithm proposed in the literature for computing a pair of SRLG-disjoint paths in networks with SRLGs satisfying the star property, and then prove that this problem is in fact NP-complete. We have also characterized instances that can be solved in polynomial time or are fixed parameter tractable, in particular when the number of SRLGs is constant, the maximum degree of the vertices is at most 4, and when the network is a directed acyclic graph. Moreover,
we have considered the problem of finding the maximum number of SRLG-disjoint paths in networks with SRLGs satisfying the star property. We have proved that such problem is NP-hard and hard to approximate. Then, we have provided exact and approximation algorithms for relevant subcases.

Let

With one third of the world population online in 2013 and an international Internet bandwidth multiplied by more than eight since 2006, the ICT sector is a non-negligible contributor of worldwide greenhouse gases emissions and power consumption. Indeed, power consumption of telecommunication networks has become a major concern for all the actors of the domain, and efforts are made to reduce their impact on the overall figure of ICTs, and to support its foreseen growth in a sustainable way. In this context, the contributors of the European Network of Excellence TREND have developed innovative solutions to improve the energy efficiency of optical networks summarized in .

Many studies have shown that energy-aware routing (EAR) can significantly reduce energy consumption of a backbone network. Redundancy Elimination (RE) techniques provide a complementary approach to reduce the amount of traffic in the network. In particular, the GreenRE model combines both techniques, offering potentially significant energy savings.

In , we enhance the MIP formulation proposed in for the GreenRE model. We derive cutting planes, extending the well-known cutset inequalities, and report on preliminary computations.

In , we propose a concept for respecting uncertain rates of redundant traffic within the GreenRE model, closing the gap between theoretical modeling and drawn-from-life data. To model redundancy rate uncertainty, the robust optimization approach in is adapted and the problem is formally defined as mixed integer linear program. An exemplary evaluation of this concept with real-life traffic traces and estimated fluctuations of data redundancy shows that this closer-to-reality model potentially offers significant energy savings in comparison to GreenRE and EAR.

The basic protocols of the Internet are point-to-point in nature. However, the traffic is largely broadcasting, with projections stating that as much as 80-90% of it will be video by 2016. This discrepancy leads to an inefficiency, where multiple copies of essentially the same messages travel in parallel through the same links. We have studied approaches to mitigate this inefficiency and reduce the energy consumption of future networks, in particular in .

Recently, there is a trend to introduce content caches as an inherent capacity of network equipment, with the objective of improving the efficiency of content distribution and reducing network congestion. In , , , we study the impact of using in-network caches and content delivery network (CDN) cooperation on an energy-efficient routing. Experimental results show that by placing a cache on each backbone router to store the most popular content, along with well choosing the best content provider server for each demand to a CDN, we can save up to 23% of power in the backbone.

In a P2P storage system using erasure codes, a data block is encoded in many redundancy fragments. These fragments are then sent to distinct peers of the network. In , we study the impact of different placement policies of these fragments on the performance of storage systems.

In , , we propose and analyze a simple localized algorithm to balance a tree. The motivation comes from live distributed streaming systems in which a source diffuses a content to peers via a tree, a node forwarding the data to its children. Such systems are subject to a high churn, peers frequently joining and leaving the system. It is thus crucial to be able to repair the diffusion tree to allow an efficient data distribution. In particular, due to bandwidth limitations, an efficient diffusion tree must ensure that node degrees are bounded. Moreover, to minimize the delay of the streaming, the depth of the diffusion tree must also be controlled. We propose here a simple distributed repair algorithm in which each node carries out local operations based on its degree and on the subtree sizes of its children.

We study the problem of gathering information from the nodes of a
radio network into a central node. We model the network of possible
transmissions by a graph and consider a binary model of interference
in which two transmissions interfere if the distance in the graph
from the sender of one transmission to the receiver of the other is

The Autonomous System (AS)-level topology of the Internet that currently comprises more than 40k ASs, is growing at a rate of about 10% per year. In these conditions, Border Gateway Protocol (BGP), the inter-domain routing protocol of the Internet starts to show its limits, among others in terms of the number of routing table entries it can dynamically process and control. To overcome this challenging situation, the design but also the evaluation of alternative dynamic routing models and their comparison with BGP will be performed by means of simulation. However, existing routing models simulators such as DRMSim, the Dynamic Routing Model Simulator developped in Coati in collaboration with Alcatel-Lucent , are limited in terms of the number of routing table entries they can dynamically process and control on a single computer.

In telecommunication networks packets are carried from a source

Coati is 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. More information on several results presented in this section may be found in R. Soares's thesis .

We use graph theory to model various network 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 from which the problems are polynomial-time solvable.

Parameterized complexity is a way to deal with intractable computational problems having some parameters that can be relatively small with respect to the input size. This area has been developed extensively during the last decade.
More precisely, we consider problems that consist in deciding whether a graph

We study the parameterized complexity of the edge-modification problems. Given a graph

We also design a unified parameterized algorithm for computing various widths of graphs (such as branched tree-width, branch-width, cut-width, etc.) .

The geodesic convexity of graphs naturally extends the notion of convexity in euclidean metric spaces. A set *convex* if any vertex on a shortest path between two vertices of *convex hull* of *hull set* of a graph is a set of vertices whose convex hull is

The Gromov hyperbolicity is an important parameter for analyzing complex networks since it expresses how the metric structure of a network looks like a tree. In other words, it provides bounds on the stretch resulting from the embedding of a network topology into a weighted tree. It is therefore used to provide bounds on the expected stretch of greedy-routing algorithms in Internet-like graphs. However, the best known algorithm for computing this parameter has time complexity in

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. We investigated several variants of these games.

We study non-deterministic graph searching where the searchers have to capture an invisible fugitive but can see him a bounded number of times. This variant generalizes the notion of pathwidth and treewidth of graphs. In this setting, we provide a polynomial-time algorithm that approximates the minimum number of searchers needed in trees, up to a factor of two .

In , , we define another variant of graph searching, where searchers have to capture an invisible fugitive with the constraint that no two searchers can occupy the same node simultaneously. This variant seems promising for designing approximation algorithms for computing the pathwidth of graphs. The main contribution in , is the characterization of trees where

We also study graph searching in directed graphs. We prove that the graph processing variant is monotone which allows us to show its equivalence with a particular digraph decomposition .

A surprising application of some variant of pursuit-evasion games is the problem for a web-browser to download documents in advance while an internaut is surfing on the Web. In a previous work, we model this problem as a Pursuit-evasion game called Surveillance game. In , , we continue our study of the Surveillance game. We provide some bounds on the connected and online variants of this game. In particular, we show that, in the online variant (when the searchers discover the graph during the game), the best strategy is the trivial one that consists in downloading the document in the neighborhood of the position of the internaut.

In , , , we define a framework generalizing and relaxing many games (including the Surveillance game) where Players use fractions of their token at each turn. We design an algorithm for solving the fractional games. In particular, our algorithm runs in polynomial-time when the length of the game is bounded by 2 (in contrast, computing the surveillance game is NP-hard even when the game is limited to two turns). For some games, we also prove that the fractional variant provides some good approximation. This direction of research seems promising for solving many open problems related to Pursuit-evasion games.

Motivated by the understanding of the limits of distributed computing, we consider a recent model of robot-based computing which makes use of identical, memoryless mobile robots placed on nodes of anonymous graphs. The robots operate in Look-Compute-Move cycles that are performed asynchronously for each robot. In particular, we consider various problems such as graph exploration, graph searching and gathering in various graph classes. We provide a new distributed approach which turns out to be very interesting as it neither completely falls into symmetry-breaking nor into symmetry-preserving techniques. We proposed a general approach , to solve the three problems in rings even in case of symmetric initial configurations.

In Coati, we have recently started a collaboration with EPI ABS (Algorithms Biology Structure) from Sophia Antipolis on “minimal connectivity complexes in mass spectrometry based macro-molecular complex reconstruction” , . This problem turns out to be a minimum color covering problem (minimum number of colors to cover colored edges with connectivity constraints on the subgraphs induced by the colors) of the edges of a graph, and is surprizingly similar to a capacity maximization problem in a multi-interfaces radio network we were studying.

Graph colouring is a central problem in graph theory and it has a huge number of applications in various scientific domains (telecommunications, scheduling, bio-informatics, ...). We mainly study graph colouring problems that model ressource allocation problems.

A well-known channel assignment problem is the following: we are given a graph *span* of the used bandwidth.

We studied a particular, yet quite general, case, called *backbone colouring*, in which there are only two levels of interference. So we are given a graph *the backone*.
Two adjacent vertices in * $q$-backbone chromatic number*
and is denoted

We also studied weighted colouring which models various problems of shared resources allocation.
Given a vertex-weighted graph *weight* of a colour class *weight* of *weighted chromatic number*. In , we prove that the Weighted Colouring Problem admits a version of Hajós' Theorem and so we show a necessary and sufficient condition for the weighted chromatic number of a vertex-weighted graph

Since many applications, and in particular channel assignment problems, must be solved on-line,
we studied on-line colouring algorithms. The most basic and most
widespread of them 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* and is denoted

With the success of moderately exponential algorithms, there is an increasing interest
for enumeration problems, because of their own interest but also because they might be crucial to solve optimization problems.
In , we are interested in computing the number of edge colourings and total colourings of a connected graph. We prove that the maximum number of

Graph theory can be roughly partitioned into two branches: the areas of undirected graphs and directed graphs (digraphs). Even though both areas have numerous important applications, for various reasons, undirected graphs have been studied much more extensively than directed graphs. One of the reasons is that many problems for digraphs are much more difficult than their analogues for undirected graphs.

One of
the cornerstones of modern (undirected) graph theory is minor
theory of Robertson and Seymour. Unfortunately, we cannot expect an equivalent for directed graphs.
Minor theory implies in particular that,
for any fixed

Let

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

"Convention de recherche encadrant une bourse CIFRE" on the topic *Graphic Processing Units for Signal Processing* with joint supervision with Aoste project.

Coati is part of the join laboratory Inria / Alcatel-Lucent Bell-labs France within the ADR Network Science and works on the fast computation of topological properties (hyperbolicity, covering, etc.) .

The project AGAPE (Parameterized and exact graph algorithms) is led by Coati and 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 consider two approaches which are closely related ways to reduce the combinatorial explosion of NP-hard problems: moderately exponential exact algorithms and fixed-parameter tractability.

Réseaux de communications, working group of GDR ASR, CNRS.

Action Graphes, working group of GDR IM, CNRS.

Title: EULER (Experimental UpdateLess Evolutive Routing)

Type: COOPERATION (ICT)

Defi: Future Internet Experimental Facility and Experimentally-driven Research

Instrument: Specific Targeted Research Project (STREP)

Duration: October 2010 - June 2014

Partners: Alcatel-Lucent Bell (leader) (Antwerp, Belgique), iMind (Ghent, Belgium), UCL (Louvain, Belgium), RACTI (Patras, Grece), UPC (Barcelona, Spain), UPMC (ComplexNetworks, Paris 6), Inria (Coati, Gang, Cepage).Coordinator: ALCATEL-LUCENT (Belgium)

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. Coati is the leader of WP3 on Topology Modelling and Routing scheme experimental analysis.

Bilateral collaboration funded by the french ministry of foreign affairs (MAE), the french ministry of research and education (MESR), and the Deutscher Akademischer Austauschdienst (DAAD). The funding covers scientific visits.

"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 Coati team at Inria Sophia-Antipolis and to address algorithmic problems in communication networks.

Title: Algorithm for large and Dynamic Networks

Inria principal investigator: Nicolas Nisse

International Partner (Institution - Laboratory - Researcher):

Universidad Adolfo Ibañez, Santiago, Chile

Facultad de Ingeniería y Ciencias

Karol Suchan

Duration: 2013 - 2015

The main goal of this Associate Team is to study the structure of networks (modeled by graphs) to design both efficient distributed algorithms and reliable network topologies suitable to applications. We are interested both in large-scale (Facebook, Internet, etc.) and in smaller networks (e.g., WDM) that handle heavy traffic. More precisely, we aim at designing new techniques of distributed and localized computing to test structural properties of networks and to compute structures (e.g., decompositions) to be used in applications. Concerning the applications, we will first focus on routing and subgraph packing problems.

There are two main objectives:

Find efficient localized algorithms to test certain graph properties or to prove that no such algorithms exist. We will formalize several distributed computing models and analyze which properties can and which cannot be tested in them.

Define graph properties – computable or approximable in distributed systems – such as structures/decompositions/representations. The driving idea is to combine several well studied graph properties in order to obtain more specific structures which we hope to be more easily computable.

To verify the practical efficiency of our results, the designed algorithms will be implemented and compared to existing ones. For this purpose, a particular effort will be put to design and implement algorithms to generate graphs that satisfy properties of interest, in order to use them to test the algorithms.

The originality of the proposal is to combine powerful tools of graphs theory (e.g., FPT complexity) and of combinatorial optimization (Mixed Integer Programming) with distributed computing. One challenge here is to balance between the degree of locality of desired algorithms and the relevance of properties that may be computed.

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.

ALERTE (ALgorithmes Efficaces pour les Réseaux de TElécommunications), with Pargo Team, Universidade Federal do Ceará, Brazil, 07/2011-07/2013.

ALgorithmes Distribués pour le calcul de la structure des réseaux, with Chile, 2013-2015.

Univ. Southern Denmark, Odensee, Denmark, from October 11 to November 2, 2013 (3 weeks);

Univ. degli studi di Perugia, Italy, September 9-17, 2013 (2 weeks);

Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, Japan, from September 16, 2013 to January 31, 2014 (4.5 months);

Univ. L’aquila, Italy, from March 1 to April 30, 2013 (2 months);

Univ. of L'Aquila, Italy, from June 22 to July 13, 2013 (3 weeks);

Concordia Univ., Montréal, Canada, February 11-22, 2013 (2 weeks);

Univ. Oran, Algeria, December 6-13, 2013 (1 week);

Tokyo Woman's Christian Univ., Suginami-ku, Tokyo, Japan, from March 21 to April 4, 2013 (2 weeks);

RWTH Aachen Univ., Germany, February 11-15, 2013 (1 week);

UFC Fortaleza, Brazil, November 5-11, 2013 (1 week);

Univ. Thessaly, Volos, Greece, March 24th-31th (1 week);

Univ. L’Aquila, Italy, September 1-8, 2013 (1 week);

Simon Frasier Univ., Vancouver, Canada, from January 20 to June 14, 2013 (5 months);

Univ. L'Aquila, Italy, September 1-9, 2013 (1 week);

Univ. Adolfo Ibañez, Chile, from September 7 to October 6, 2013 (1 month);

Univ. Adolfo Ibáñez, Chile, September 7-21, 2013 (2 weeks);

Univ. Oran, Algeria, June 12 till July 13, 2013 (1 month);

Abbotsford and SFU, Vancouver, Canada, from March 1 to April 19, 2013 (1 month 1/2);

ENS Cachan, from March 18, 2013 until August 31, 2013, and since October 15, 2013;

Univ. Federal do Ceará, Brazil, since November 2013;

Univ. Adolfo Ibañez, Chile, since December 2013;

National and Kapodistrian Univ. Athens, Greece, from March 2013 until September 2013;

Univ. Central Greece, from January 2013 until July 2013;

Univ. São Paulo (USP), Brazil, from March 2013 until July 2013;

Univ. Federal do Ceará, Brazil, since November 2013;

Visit to Simon Fraser Univ., Vancouver, Canada (January 11-February 10, 2013).

LRI, Orsay (March 29, 2013); LIRMM, Montpellier (April 16, 2013);

Visit to Univ. Adolfo Ibañez (part of EA AlDyNet), Santiago Chile (November 15-30, 2013);

Visit to LIRMM, Univ. Montpellier 2, (December 9-11, 2013);

Visit to Concordia Univ., Montreal, Canada, (August 1st-September 1st, 2013);

Visit to Univ. Adolfo Ibañez, Santiago, Chile, (November 14-December 12, 2013);

Visit to Univ. Adolfo Ibañez (part of EA AlDyNet), Santiago Chile (November 15-December 1st, 2013); Visit to Univ. Perugia, Italy (October 20-25, 2013)

Expert for DRTT, and various projects outside France (Canada, Italy,...); Member of the Ph.D. committee of the University of Marseille;

Member of the *comité du suivi doctoral* of Inria Sophia Antipolis (since January 2009); Member of the scientific board of the GIS ENSL-UNS (CNRS, ENSL, Inria, UNS) since 2011; Expert for the Future and Emerging Technologies Open Scheme (FET-Open) European program, and the ANR;

Member of the *conseil de laboratoire I3S*;

Responsible of the Pôle ComRed of I3S (since September 2013); Expert for the ANR and its Czech analogues; Member of the *conseil de l'Ecole Doctorale I2S* (Montpellier);

Member of the commission ad-hoc ATER 27 UNS; Member of *Comité Permanent de Ressources Humaines* (CPRH) UNS 27e; Member of the *conseil de département* (Department Committee) of IUT Nice; Expert for DRTT PACA.

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, SIAM book series on Discrete Mathematics, Transactions on Network Optimization and Control, Discrete Mathematics, Algorithms and Applications;

Discrete Applied Mathematics (Elsevier); Networks (Wiley);

Discrete Mathematics and Theoretical Computer Science;

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

GT Graphes du GDR IM du CNRS; Journée Combinatoire et Algorithmes du Littoral Méditerranéen;

this scientific event comprises the *European Symposium on Algorithms* (ESA), the *Workshop on Algorithms for Bioinformatics* (WABI), the *International Symposium on Parameterized and Exact Computation* (IPEC), the *Workshop on Approximation and Online Algorithms* (WAOA), the *International Symposium on Algorithms for Sensor Systems, Wireless Ad Hoc Networks and Autonomous Mobile Entities* (ALGOSENSORS), the *Workshop on Algorithmic Approaches for Transportation Modeling, Optimization, and Systems* (ATMOS), and the *Workshop on Massive Data Algorithmics* (MASSIVE). Sophia Antipolis, France (September 2-6, 2013); D. Coudert and J. Moulierac were members of the organizing committee.

17th International Conference On Principle Of DIstributed Systems; Conference Chair: N. Nisse; Organization Committee: A. Kodjo, B. Li.

IEEE ICC – Green Communications and Networks Track, Budapest, Hungary (June 9-13, 2013); IEEE GLOBECOM – Green Networks and Communication Systems Track, Atlanta, GA, USA (December 9-13, 2013); 17th International Conference on Optical Network Design and Modeling (ONDM'13), Brest, France (April 16-19, 2013);

15emes Journées Graphes et Algorithmes, Orsay, France (November 13-15, 2013);

PC Chair of the 15th Rencontres francophones sur les aspects algorithmiques des télécommunications (AlgoTel) (May 28-31, 2013);

DIMACS Workshop on Algorithms for Green Data Storage, DIMACS, Rutgers University USA (December 18, 2013);

Bell labs - NIST Workshop on Large-Scale Networks, Murray Hill, NJ, USA (October 25, 2013); AlDyNet Workshop on Algorithms and Randomness, Santiago , Chile (November 21, 2013);

School on Graph Theory, Oléron, France (June 17-21, 2010), five hour lecture on “Orientations and colorings of graphs”;

AlDyNet Workshop on Algorithms and Randomness, Santiago , Chile (November 21, 2013);

Meeting of ADR Network Science of the Alcatel-Lucent / Inria Joint lab, Paris, France (February 28, 2013) Attended by D. Coudert (speaker) and N. Nisse (speaker); Sophia-Antipolis, France (December 5) Attended by D. Coudert;

Journée du pôle COMRED (December 3-4, 2013). Attended by all members of COATI;

Journées de l'ANR - Rencontres du numérique (April 17-18, 2013). Attended by F. Giroire;

Plenary meeting of FP7 STREP EULER , Antwerp, Belgium (September 23-25, 2013). Attended by D. Coudert and A. Lancin.

GreenDay@Lille, Lille, France (November 28-29, 2013). Attended by K. Phan;

29e Journee Francilienne de Recherche Operationnelle, Paris, France (June 4, 2013). Attended by J. Araújo, B. Li, N. Nisse;

15èmes Journées Graphes et Algorithmes, Orsay, France (November 13-15, 2013). Attended by J. Araújo, F. Havet, A. Maia (speaker);

Journées D'informatique fondamentale de Paris Diderot (April 24, 2013). Attended by N. Nisse;

Journées Scientifiques and Journée REP of Inria, Rennes, France (June 25-27, 2013). Attended by D. Coudert;

Kick off meeting Phase 2 of the Common Lab Inria-Alcatel Lucent Bell Labs, Nozay, France (March 27, 2013). Attended by J-C. Bermond;

Polyèdres et Optimisation Combinatoire: Journée sur l'Optimisation Robuste et la programmation mathématique Paris, France (December 6th, 2013). Attended by A. Kodjo;

meeting for preparing submission of ANR SEAT (October 2nd, 2013). Attended by D. Coudert and N. Nisse;

Meeting on Combinatorics and Distributed Computing, Pont-à-Mousson, (November 12-15, 2013). Attended by F. Havet;

NoE TREND Plenary Meeting, Catania, Italy (February 6-8, 2013). Attended by F. Giroire;

AlDyNet Workshop on Algorithms and Randomness, Santiago, Chile (November 21, 2013). Attended by D. Coudert (speaker), B. Li (speaker), F. Moataz (speaker), N. Nisse (speaker);

Sophia Antipolis, France (September 2-6, 2013). Attended by all members of COATI;

15èmes Rencontres Francophones pour les Aspects Algorithmiques des Telecommunications, Pornic, France (May 28-31, 2013). Attended by F. Moataz (speaker), N. Nisse, D. Coudert, G. Ducoffe (speaker), I. Tahiri, A. Lancin, R. Soares (speaker) and F. Giroire;

Working group and Workshop on Algorithms for Green Data Storage, DIMACS, Rutgers University USA (December 16-18, 2013). Attended by J-C. Bermond (speaker);

the 9th International Conference on Design of Reliable Communication Networks, Budapest, Hungary (March 4-7, 2013). Attended by F.Z. Moataz (speaker);

26th European Conference on Operational Research, Roma, Italy (July 2-4, 2013). Attended by C. Molle-Caillouet (speaker), D. Coudert and N. Nisse (speaker);

Global Information Infrastructure and Networking Symposium, Trento, Italy (October 28-31, 2013). Attended by A. Kodjo (speaker);

6th International Conference on Data Management in Cloud, Grid and P2P Systems, Prague, Czech Republic (August 28-29, 2013). Attended by R. Modrzejewski (speaker);

IEEE Global Communications Conference, Atlanta, United States (December 9-13, 2013). Attended by F. Giroire (speaker);

6th workshop on Graph Classes, Optimization, and Width Parameters, Santorini Island (October 09–11, 2013). Attended by F. Havet (speaker) and N. Nisse;

IEEE International Conference on Communications, Budapest, Hungary (June 912, 2013). Attended by R. Modrzejewski (speaker);

IEEE International Conference on Green Computing and Communications, Beijing, China (August 20-23, 2013). Attended by K. Phan (speaker);

6th International Network Optimization Conference, Tenerife, Spain (May 20-22, 2013). Attended by I. Tahiri (speaker);

VII Latin-American Algorithms, Graphs and Optimization Symposium, Playa del Carmen, Mexico (April 22-26, 2013). Attended by J. Araújo (speaker), A. Maia (speaker), P. Moura (speaker), R. Soares (speaker);

17th International Conference On Principle Of DIstributed Systems, Nice, France (December 16-18, 2013). Attended by B. Li, A. Kodjo and N. Nisse

20th International Colloquium on Structural Information and Communication Complexity, Ischia, Italy (July 1–3, 2013). Attended by F. Giroire (speaker) and N. Nisse (speaker);

Bell labs - NIST Workshop on Large-Scale Networks, Murray Hill, NJ, USA (October 25, 2013). Attended by D. Coudert;

School on Constraint Satisfaction problems, ENS Lyon, France (January 21-25, 2013). Attended by F. Moataz;

Summer School on Graph and Routing Dynamics: Models and Algorithms, Barcelona, Spain (July 1-5, 2013). Attended by F. Moataz, B. Li and A. Lancin;

13es Journées Combinatoire et Algorithmes du Littoral Méditerranéen, Marseille, France (June 10-11, 2013). Attended by J. Araújo, G. Ducoffe, F. Giroire, A. Maia, N. Nisse;

14es Journées Combinatoire et Algorithmes du Littoral Méditerranéen, Barcelona, Spain (October 14-15, 2013). Attended by F. Havet (speaker), A. Maia

Winter School on Network Optimization, Estoril, Portugal (January 14-18, 2013). Attended by B. Li and A. Kodjo;

Summer school ResCom 2013 of GDR ASR of CNRS on Content Centric Networks, Porquerolles, France (May 13-17, 2013). Attended by J-C. Bermond, D. Coudert, F. Giroire, R. Modrzejewski;

Summer School on Graph Theory, île d'Oléron, France (June 17-21, 2013). Attended by J. Araújo, F. Havet, B. Li, A. Maia, F. Moataz, N. Nisse;

The TREND PhD School in Green Networking, Turin, Italy (July 1-5, 2013). Attended by K. Phan;

Licence: A. Kodjo, Algorithme-Programmation Objet-Python, 40h ETD, L2, Networks, 15h ETD, L2, IUT Nice Côte d'Azur, Informatique pratique, 36h ETD, L1,Univ. Nice Sophia Antipolis;

Licence: F. Moataz, Systèmes Informatiques, 40h ETD, L1, Univ. Nice Sophia Antipolis;

Licence: C. Molle-Caillouet, IT Tools, 53h, L1, Database and advanced information system, 36h, L2, Operations Research, 81h, L2, Delivery Optimization, 30h, L3, IUT Nice Côte d'Azur, Univ. Nice Sophia Antipolis;

Licence: J. Moulierac, Algorithms and Programming, 100h ETD, L1, ASR5 - Networks, 30h ETD, L1, IUT Nice Côte d'Azur, Univ. Nice Sophia Antipolis;

Licence: N. Nisse, informatique, 30h ETD, 1ère année classes préparatoires (L1), CIV, Sophia Antipolis, France;

Licence: I. Tahiri, Introduction to networks, 96h ETD, L1, IUT Nice Côte d'Azur, Univ. Nice Sophia Antipolis;

Licence: M. Syska, Introduction to Operating Systems, 40h ETD, L1, Operating Systems : Advanced Programming, 60h ETD, L2, Bash Scripting, 20h ETD, L3, Introduction to Algorithms, 30h ETD, L3, Linux Systems Administration, 40h ETD, L3, IUT Nice Côte d'Azur, Univ. Nice Sophia Antipolis.

Master: D. Coudert, Algorithms for Telecommunication 2, 30 ETD, M2 Ubinet of Master IFI, Univ. Nice Sophia Antipolis;

Master: F. Giroire, 16h ETD, Introduction to Probabilities and Statistics, International track of the Master 1 IFI, Univ. Nice Sophia Antipolis;

Master: F. Giroire and N. Nisse, Algorithms for Telecommunications, 30h ETD, M2 Ubinet of Master IFI, Univ. Nice Sophia Antipolis;

Master: F. Giroire and N. Nisse, Algorithms for Telecommunications, 36h ETD, M2, Master MDFI, Univ. Marseille;

Master: F. Havet, Discharging Method, 6h, M2, Simon Fraser University, Canada.

Master: A. Kodjo, Réseaux, 15h ETD, M1, Univ. Nice Sophia Antipolis;

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

J. Moulierac is Directrice d'études of Semestre 2 décalé at IUT Nice Côte d'Azur, Computer Science Department since september 2013;

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

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

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
(http://

**PhD:**

R. Modrzejewski, *Systèmes pair-à-pair de partage de données*, October 24, 2013, S. Pérennes and F. Giroire.

R. Pardo Soares, *Routing reconfiguration in WDM networks*, November 8, 2013, D. Coudert, C. Linhares Sales and N. Nisse.

**PhD in progress:**

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

*4th 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.

*3rd year:*

M. A. Bergach, *GPGPU Graphics Processing Units for signal processing*, since September 2011, M. Syska.

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

B. Li, *Tree-decomposition and applications to routing*, 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.

*2nd year:*

F. Z. Moataz, *Conception et optimisation de réseaux robustes aux pannes et variations de capacités*, since October 2012, D. Coudert.

supervised the internship of Guillaume Ducoffe (ENS Cachan, Paris, France) on "Computation in Large Graphs with Applications to Gromov Hyperbolicity", March-September 2013 (6 months);

supervised the internship of Mathieu Schmitt (École Normale Supérieure de Lyon, France) on backbone colouring, May-August 2013 (3 months).

supervised the internship of Christos Papageorgakis (University of Thessaly, Volos, Greece) on implementation of Cops and Robber games, February-July 2013 (6 months);

supervised the internship of Ioannis Lamprou (University of Athens, Greece) on fractional games in graphs, March-August 2013 (6 months);

member of the PhD jury of Remigiusz Modrzejewski, Univ. Nice Sophia Antipolis (October 24, 2013);

Member of the PhD jury of Valentin Weber, Université de Grenoble, France (July 8, 2013); Referee and member of the PhD jury of Jiyai Liu, Télécom Bretagne, Rennes, France (November 4, 2013); Member of the PhD jury of Ronan Soares, Univ. Nice Sophia Antipolis, France (November 8, 2013); Member of the PhD jury of Christian Glacet, Université de Bordeaux 1, Bordeaux, France (December 6, 2013);

member of the PhD jury of Ngo Hoang Giang, Univ. Nice Sophia Antipolis (December 16, 2013); member of the PhD jury of Remigiusz Modrzejewski, Univ. Nice Sophia Antipolis (October 24, 2013);

external referee of the PhD of S. Simonsen, University of Southern Denmark (November 7 2013); external referee of the PhD of A. Maddaloni, University of Southern Denmark (November 8 2013);

member of the PhD jury of Ronan Soares, Univ. Nice Sophia Antipolis (November 8, 2013);

J-C. Bermond is in charge of the attractiveness of the center Inria Sophia Antipolis Méditerannée. Among other activities he corganized The "Mediterranean days" (January 23-25) ( 25 foreign students invited) and co-organized the valorization afternoon on February 2, 2013 (100 students);

F. Giroire presented the stand "Magie et jeux mathématiques" at the Centre International de Valbonne, France (October 8, 2013); F. Moataz assisted the stand "Drone/Unmanned Aerial Vehicle" at Sophia Antipolis, France (October 12-13, 2013);

J. Aráujo has given lectures on Graph Theory and Algorithms to PhD students, 20h;

J-C. Bermond gave a vulgarization talk at the Centre Culturel of La Grande Motte, Hérault France (April 16, 2013);

J-C. Bermond gave 3 talks to investors on the future of optimization in networks, Paris (March 28, 2013);

N. Nisse explains graph to a Lycée class at Marseille, France (December 19th, 2013);