Maestrois a joint project-team of Inria, Cnrsand the University of Montpellier II (through the Lirmmlaboratory), based in Sophia Antipolis and in Montpellier. It is concerned with the modeling, performance evaluation, optimization and control of discrete-event dynamical systems ( Deds), with a particular emphasis on networks and their applications. The scientific contributions are both theoretical, with the development of new modeling formalisms, and applied with the development of software tools for the performance evaluation of Deds.

Research activities in 2005 have focused on the following issues:

performance evaluation of wireless, mobile, ad hoc and sensor networks, in particular within a research grant from France Telecom R&Dand the support of Cefipra(French-Indian collaboration)

development of online statistical estimators of data flow characteristics with small memory consumptions, supported by the Acigrant Flux

performance evaluation of peer-to-peer protocols using stochastic fluid models, with the support of France Telecom R&Dand Network of Excellence Euro-Ngi

analysis of processor-sharing scheduling disciplines, with the support of France Telecom R&Dand Network of Excellence Euro-Ngi

probabilistic and graph theoretical methods for the Web search engines in the framework of Egide Eco-Netprogramme

dynamic aspects of the coverage of a mobile sensor movement with the support of the Nsf Itrproject ``QoS in the Future Internet''

singularly perturbed Markov chains and time-average optimal control in the framework of the French-Australian grant ``Linkage International''

The main mathematical tools and formalisms used in Maestroinclude:

theory of stochastic processes: Markov process, point process, Palm measure, large deviations

theory of dynamical discrete-event systems: queues, fluid approximation, network calculus

theory of control and scheduling: dynamic programming, Markov decision process, game theory, deterministic and stochastic scheduling, pathwise comparison

theory of singular perturbations

random matrix theory.

Our main application area is networking and in particular, modeling, performance evaluation, optimization and control of protocols and network architectures. It includes:

Internet: TCP, high speed congestion control, voice over IP, service differentiation, quality of service, multicast applications, content distribution systems, peer-to-peer systems, overlay networks, multimedia traffic generation

Wireless (cellular, ad hoc, sensor) networks: power control, medium access control, transmission rate control, redundancy in source coding, mobility models, coverage

Satellite communications: IP over satellite links, planning and resource allocation.

Maestrohas developed two softwares, Allegro, a multimedia traffic generator (see 2004 Maestroactivity report for a brief description of Allegrofunctionalities) and Ers, a set of tools for the analysis of discrete-event systems. These softwares can be downloaded from http://www-sop.inria.fr/maestro/soft/allegro.htmland http://www-sop.inria.fr/mistral/soft/ers.html, respectively.

Due to the rapid increase of the bandwidth in networks (with links up to 10Gbps), the mechanisms of most of the existing versions of TCP that adapt to the available bandwidth turn out to be too slow, and need sometimes hours until they manage to grab the available bandwidth. Recently, new versions of TCP have been proposed which implement more aggressive mechanisms for adapting to the available throughput. High Speed TCP (proposed by S. Floyd) and Scalable TCP (proposed by T. Kelly) are two such mechanims.

TCP is frequently modeled as a fluid whose amount increases smoothly until a loss occurs, in which case the fluid drops instantaneously to a lower level. This is the well-known saw-tooth model of the TCP sending rate evolution. An instance of this model can be found in , where E. Altman and K. Avrachenkov, in collaboration with C. Barakat ( Inriaproject-team Planete), have revisited their Sigcomm 2000 paper with more detailed discussions on ergodicity conditions for the TCP sending rate evolution, the derivation of the second moment of the TCP sending rate, and the numerical experiments.

Yet other fluid models have been used (in particular by F. P. Kelly) in which the increase and decrease parts of the TCP dynamics are replaced by their average value, so that TCP dynamics are described using a differential equation (referred below to as the smooth fluid model). In , E. Altman, in collaboration with R. Márquez and S. Sole-Alvarez (both from the University of Los Andes, Merida, Venezuela), has shown that the smooth fluid model provides a good approximation of the saw-tooth model.

In , K. Avrachenkov, in collaboration with U. Ayesta ( Cwi, The Netherlands) and A. Piunovskiy (University of Liverpool, UK), studies the optimal choice of the buffer size in Internet routers. The objective is to determine the minimum value of the buffer size required in order to fully utilize the link capacity. There are some empirical rules for the choice of the buffer size. The most known rule of thumb states that the buffer length should be set to the bandwidth delay product of the network. Several recent works suggest that, as a consequence of the traffic aggregation, the buffer size should be set to smaller values. The analytical results in provide further evidence that indeed the buffer size should be reduced in the presence of traffic aggregation. Furthermore, their result states that the minimum required buffer is smaller than what previous studies suggested.

Consider permanent TCP sessions that share an intelligent bottleneck router. When the sum of the TCP rates reach the throughput capacity then a loss (or a congestion notification) occurs. It is assumed that the router decides which of the sessions will receive a notification (or will suffer a loss). Examples of such policies include (i) independent marking, (ii) choosing the flow with the largest throughput for marking, (iii) choosing the flow with the smallest throughput, (iv) choosing the flow for marking with a probability that is proportional to its rate. Surprisingly it has been shown that no matter what policy is used, the sum of TCP throughputs will be the same. However, the second moments do depend on the used marking policy. The above results have been obtained for two connections by E. Altman, in collaboration with R. El Azouzi (University of Avignon, France), D. Ros and B. Tuffin (both from Inriaproject-team Armor), and extended to any number of connections by E. Altman and D. Barman, in collaboration with B. Tuffin and M. Vojnovic (Microsoft Research, Cambridge, UK).

TCP was designed to provide reliable end-to-end delivery of data over unreliable networks. In practice, most TCP deployments have been carefully optimized in the context of wired networks. Ignoring the characteristics of wireless Mobile Ad Hoc Networks (MANETs), such as high bit error rates, path asymmetry, network partitions, route failures, power constraints, etc. lead to TCP implementations with poor performance. In , A. Al Hanbali, E. Altman and P. Nain review proposals recently made to improve the performance of TCP in MANET environment.

A. Jean-Marie, T. Alemu and Y. Calas have pursued the investigation of the interaction of FEC and the queue management algorithms, specifically, RED (Random Early Detection) and the standard Drop Tail (DT). The problem was to derive quantitative rules enabling to decide when one
situation is better than the other. The critical object here is the process of losses. Several models, including a batch-Poisson process, have been analyzed. This last one allows the authors to derive asymptotic laws, involving moments of the
*loss run length*, which explains the presence of a cross-over phenomenon when the packet loss rate increases. Simulations of networking situations illustrate the qualitative validity of the predictions
,
,
.

In the framework of the FLUX project (funded by the ACI Masses of Data), A. Jean-Marie and O. Gandouet have focused on the problem of recognizing long-lived and short-lived data flows (elephants and mice) using algorithms with a (very) small memory. The modeling of the problem reduces it to the estimation of some characteristics of multi-sets, like moments of frequencies, or the number of elements with specific properties. Algorithms based on probabilistic counting seem to offer this possibility. From there, they have explored two directions.

On one side, they have studied the intrinsic algorithmic difficulty of the question. Using results from the theory of ``communication complexity'', they have proved that no online algorithm could solve the problem in general with substantially less memory than an exact algorithm. This result holds whether the algorithm is exact or probabilistic.

On the other side, an algorithm allowing the estimation of the number of elephants in a flow of packets (an elephant being defined as having more than k times as much packets than a mouse) has been constructed, on the basis of the LogLog algorithm of Durand and Flajolet. For multi-sets in a specific (yet practical) family, this algorithm indeed uses much less memory than an exact algorithm.

In secure multicast communications (etc. TV over IP, confidential videoconferences) a hierarchical organization of encryption keys is often adopted to minimize the costs of updating the data encryption key at all members. However, volatile members still induce a high number of updates needed to ensure data confidentiality. It has been proposed to isolate these members to improve the quality of service rendered to long-lived members. In , S. Alouf, A. Jean-Marie and P. Nain develop a stochastic model of the system, the objective being to optimally tune its parameters. In particular, the joint distribution of disjoint populations in a M/G/ system is derived yielding the joint distribution of the populations at hand (ongoing work).

A. Jean-Marie and L. M. Ngo have analyzed one aspect of the RMUS protocol, which has been proposed for flow control in the satellite-based AI3 system (Asian Internet Interconnection Initiatives Project). This study led to the conclusion that the acknowledgment implosion problem may impede the scalability of the protocol. The results will appear in .

IEEE 802.11 represents the de facto standard for wireless local area networks. One of the well-known drawbacks of IEEE 802.11 is the low performance of its MAC protocol in terms of throughput in congested networks.

During his master internship, supervised by S. Alouf, M. Ibrahim has proposed an adaptive back-off mechanism whose contention window is set to an optimal size after a successful transmission. The proposed algorithm, called ``Adaptive BEB'', relies on on-line counts of error-free frames received at a given station. The optimality achieved by Adaptive BEB refers to a maximum overall system throughput. Simulation results show that Adaptive BEB substantially improves the IEEE 802.11 standard and that its performance is steady under a variety of network conditions and configurations .

The work concerns applications of random matrix theory and unitary random matrix theory to cellular networks. In most cases of interest, explicit formulas depending only on a few meaningful system parameters can be derived.

Standard studies of uplink CDMA schemes assume a multiple access communication scheme, where each user modulates his signal with a pseudo-random i.i.d. sequence. In , N. Bonneau and E. Altman, in collaboration with M. Debbah and G. Caire ( Institut Eurecom), investigate the possible gain of using orthogonal spreading codes in the uplink CDMA. The problem is analyzed in the asymptotic regime. The results are based on random unitary matrix theory.

Orthogonal Frequency Division Multiplexing Access (OFDMA) is a technique allowing multiple users to simultaneously transmit to a base station. The bandwidth is divided into carriers on which users send their information. However, efficient algorithms to schedule transmission tend to consume too many resources, because of the feedback requirements. Using the reciprocity of the channel on each carrier, N. Bonneau and E. Altman, in collaboration with M. Debbah ( Institut Eurecomand A. Hjørungnes (UniK, Norway) show in how to optimize the use of OFDMA carriers in a decentralized context in which the choice of carriers is done at the transmitters rather than at the base station. This can be most relevant to 802.16 (WiMax) where FDMA is used.

In MANETs (Mobile Ad Hoc Networks) a route between two nodes often experiences failure when the mobility of nodes increases. This explains the poor performance of traditional ad hoc routing protocols. A well-known solution proposed, and analyzed by Tse and Grossglauser, is to use
intermediary nodes as relay nodes. A relay node stores in its buffer packets for other nodes, and then transmit a packet when it is sufficiently close to the destination. In
, A. Al Hanbali, A. A. Kherani, R. Grenovelt, P. Nain, and E. Altman study the contribution of a relay node
in relaying data between a source and a destination, called
*relay throughput*. When all nodes move according to the same mobility model, a uniform steady-state node position distribution achieves the lowest relay throughput. Explicit and closed form expressions for the relay throughput are provided for the Random Waypoint and The Random
Direction mobility models, in both one and two dimensions. In addition, for the Random Walk mobility the mean waiting time of the packet in the relaying buffer of a relay node is derived for the high load case.

R. Groenevelt and P. Nain (in collaboration with G. Koole from the Vrije Universiteit of Amsterdam, The Netherlands) have introduced in a generic stochastic model that accurately predicts the message delay in a mobile ad hoc network when nodes can relay messages. The model has only two input parameters: the number of nodes and the intensity of a finite number of homogeneous and independent Poisson processes modeling instances when any pair of nodes come within transmission range of one another. Explicit expressions are obtained for the Laplace-Stieltjes transform of the message delay, from which the expected message delay is derived in closed-form. These calculations are carried out for two relay protocols: the two-hop relay and the unrestricted relay protocols. Despite its simplicity, the model is able to accurately predict the performance of both relay protocols for a number of mobility models (Random Waypoint, Random Direction and Random Walker Mobility Models), as shown by simulations.

One important issue in ad hoc wireless networks is the characterization of the limiting performance, in terms of both connectivity and coverage. After studying in 2004 one-dimensional networks using a queueing theory approach, E. Altman, in collaboration with D. Miorandi ( Create-Net, Italy), has studied in the two-dimensional problem under various assumptions on the channel gains.

E. Altman, K. Avrachenkov and G. Miller, along with R. Márquez (University of Los Andes, Merida, Venezuela), have worked on the problem of decentralized dynamic control of power and transmission rate in cellular networks. It is assumed that each mobile knows only the state of its own channel, and takes decisions on the power levels based on that information. For each mobile, its SINR (which is the ratio between the power received at a base station from the mobile and the sum of the powers corresponding to interferences from other mobiles and of noize) determines the transmission rate that the mobile can achieve. In the authors consider the case of two mobiles, where the first mobile seeks for a power control strategy so as to maximize its transmission rate, whereas the other mobile, assumed to be malicious, tries to minimize the rate of the first mobile by the intereference that it causes. Both mobiles have constraints on their average power consumption. This problem is formulated as a stochastic zero-sum game, with a non-standard information structure. Foundations for solving such problems are laid in , and then implemented to derive structural properties of the optimal policies for each of the mobiles.

Surfers on the Internet frequently use search engines to find pages satisfying their queries. However, there are typically hundreds or thousands of relevant pages available on the Web. Thus, listing them in a proper order is a crucial and non-trivial task. PageRank is one of the main criteria according to which Google ranks Web pages. PageRank can be interpreted as a frequency of visiting a Web page by a random surfer and thus it reflects the popularity of a Web page. Google computes the PageRank using the power iteration method which requires about one week of intensive computations. In K. Avrachenkov, D. Nemirovsky and N. Osipova, in collaboration with N. Litvak (University of Twente, The Netherlands), propose and analyze Monte Carlo type methods for the PageRank computation. There are several advantages of the probabilistic Monte Carlo methods over the deterministic power iteration method: Monte Carlo methods provide good estimation of the PageRank for relatively important pages already after one iteration; Monte Carlo methods have natural parallel implementation; and finally, Monte Carlo methods allow for continuous updates of the PageRank as the structure of the Web changes.

F. Clévenot-Perronnin and P. Nain, in collaboration with K. W. Ross (Polytechnic University, New York, USA), have investigated service differentiation and bandwidth diversity issues for BitTorrent like P2P networks. In they introduce resource allocation strategies that are based on a single parameter. With the help of multiclass fluid models they show how this parameter could be tuned so as to achieve a target quality of service ratio.

In , F. Clévenot-Perronnin and P. Nain propose a new model of Squirrel, a P2P cooperative web cache. This work extends the analysis in to an arbitrary number of nodes and to documents with different popularities.

Within the framework of non-cooperative game theory. N. Bonneau and E. Altman, in collaboration with M. Debbah ( Institut Eurecom), have introduced evolutionary games in the context of unslotted ALOHA in . The evolutionary game framework is used for large populations that have many local interactions, each involving a small number of users. The equilibrium notion introduced by Smith in 1972 in biological context is called an Evolutionarily Stable Strategy (ESS). A strategy for various behaviors within one or more types of populations is an ESS if it is immune against mutations. The authors have identified conditions for the existence of non trivial ESS and have computed them explicitly for the ALOHA scheme.

In , E. Altman, jointly with T. Boulogne (University of Paris 6), T. Jimenez and R. El Azouzi (both from University of Avignon, France) and L. Wynter (IBM T. J. Watson Research Center, New York, USA), surveys the applications of games to networks. The emphasis is on non-cooperative games but they cover in part cooperative ones. In , E. Altman only focuses on applications of game theory to queueing systems, and presents various queueing problems such as where and when to queue, how much to queue etc.

Conjectures have been introduced in game theory in an attempt to model anticipations formed by players in the absence of a complete information. Equilibria reached in a game with conjectures are called "conjectural equilibria". In static games, the structure of a conjecture is rather simple and well understood. When the game is dynamic in discrete-time, several structures are possible In a joint paper with M. Tidball ( Inra, Montpellier), A. Jean-Marie establishes the relationships that exist between these dynamic conjectural equilibria and the classical Nash-feedback equilibria .

E. Altman has pursued his work on a class of discrete-time stochastic recursive sequences of the form
X_{n+ 1}=
A_{n}(
X_{n}) +
B_{n}, where
X_{n}and
B_{n}are column vectors taking nonnegative values, and where
A_{n}is some non-negative random field. It is assumed that
{
B
_{n}}is a stationary and ergodic process (allowing, in particular, for arbitrary time-correlations) and that
{
A
_{n}}is a renewal sequence. In
stability conditions of the sequence
{
X
_{n}}have been established, and
E[
X_{n}]and
E[
X_{n}X_{n+
k}]have been computed in steady-state for any
k0. These results have been applied to the study of the infinite server queue in discrete-time in the presence of time-correlated arrivals.

In , , R. Groenevelt and E. Altman use this formalism to compute the expected waiting time in two-queue polling systems with correlated vacations.

As a natural multi-class generalization of the well-known (egalitarian) PS service discipline, Discriminatory Processor Sharing (DPS) is of great interest in many application areas, including telecommunications. Under DPS, the mean response time conditional on the service requirement is only available in closed-form when all classes have exponential service requirement distributions. For generally distributed service requirements, Fayolle et al. showed that the expected conditional response times satisfy a system of integrodifferential equations. In , K. Avrachenkov, in collaboration with U. Ayesta ( Cwi, Amsterdam) and P. Brown ( France Telecom R&D, Sophia Antipolis) and S. Nũnez Queija ( Cwi, Amsterdam), uses that result to prove that, for each class, the expected unconditional response time is finite and that the expected conditional response time has an asymptote, when the system is stable.

The asymptotic bias of each class is found in closed-form. The latter involves the mean service requirements of all classes and the second moments of all classes but the one under consideration. The authors also study DPS as a tool to achieve size-based scheduling, and provide guidelines as to how the weights of DPS must be chosen such that DPS outperforms PS.

In collaboration with Ger Koole (Vrije University, Amsterdam, The Netherlands), Dieter Fiems and Philippe Nain investigate in discrete-time preemptive repeat identical queueing systems. The high- and low-priority interarrival times are assumed to be geometrically distributed and deterministic, respectively whereas the service times are assumed to be deterministic for both classes. As an application, the queueing model is used to assess waiting times of scheduled patients in the presence of emergency arrivals.

Maestrohas pursued its collaboration with France Telecom R&Dat Issy les Moulineaux within a new two-year research grant (Contrat de Recherche Externaliseé, Cre). In 2005 new policies for scheduling TCP connections between dedicated and shared channels in UMTS have been proposed, and a patent containing these results is being filled. Coordinators of this Creare E. Altman for Maestroand J. M. Kelif for France Telecom R&D.

Since January 2005 Maestrohas been involved in a two-year research grant ( Cre) with France Telecom R&Din Sophia Antipolis, on the theme ``Internet Traffic Management and Modeling.'' Several joint working seminars between Maestroand the group at France Telecom R&Dhave been organized in 2005. Recent advances in congestion control for high speed networks and size-based scheduling have been reviewed. Key problems have been identified and their analysis will be pursued during the year 2006. Coordinators of this Creare P. Brown for France Telecom R&Dand P. Nain for Maestro.

The topic of this collaboration was the design of efficient online scheduling policies for payloads. The specificities of the problem include various temporal and feasibility constraints, and a stochastic environment. A mathematical modeling of the problem was proposed, and several dynamic scheduling policies studied with the help of a specially-designed simulator. This contract was executed jointly with Ph. Chrétienne and E. Hyon from Lip6, Paris.

Maestrois a member of the Network of Excellence (NoE) Euro-Ngion ``Design and Engineering of the Next Generation Internet, Towards Convergent Multi-Service Networks''. E. Altman is co-coordinator of the work package on control and optimization in telecommunication networks.

In 2005 Maestrohas been involved in two one-year Euro-NgiSpecific Joint Research Projects: JRA.S.07: Cellularand JRA.S.11: Fairness.

Cellular(project coordinator: T. Chahed from Get) focuses on Cross-layer Protocol Design for Wireless Networks. Within this project two postdoctoral students visited Maestro: L. Cottatellucci (three months) and U. Ayesta (one month with Maestroand three months with other teams of Cellular).

Fairness(project coordinator: P. Nain) is devoted to Fair and Efficient Scheduling in Wired and Wireless Networks. R. Núñez Queija, U. Yechiali and U. Ayesta visited Maestrowithin this project.

Maestrotogether with Cnrs(J.-B. Lasserre, H. Frankowska), University of Paris Dauphine (J.-P. Aubin), University of Utrecht (A. Gnedin) and University of South Australia (V. Ejov, J. Filar, L. Finlay, V. Gaitsgory, P. Howlett) participates in a three-year (2005-2007) international cooperation grant, Linkage International, of the Australian Research Council on the subject of ``Singular Perturbations and Multiscale Models in Optimization and Control.''

Since April 2003 Maestrohas been involved in a three-year research grant with Prof. A. Kumar and Prof. A. Chockalingam, both from IISc(Bangalore), and with Prof V. S. Borkar from TataInstitute of Fundamental Research (Mumbai). The coordinators of this project are Prof. Kumar and E. Altman for the Indian and French institutions, respectively. The theme of the cooperation is ``New Strategies for Wireless Communication Networks.'' This cooperation financed the two-year postdoctoral position at Inriaof A. A. Kherani. Within this program, D. Kumar visited the Indian Institute of Technology, Delhi, India (August 1-5, 2005) and the Indian Institute of Science, Bangalore, India (August 8-26, 2005). Moreover, R. Vennkatesh, a Ph.D. of Prof. Kumar from IIScvisited Maestrofor three weeks in October 2005. We have extended our cooperation with IIScthrough the visit of Prof. V. Sharma to Maestro.

The Auroraproject is a joint research program funded by the Research Council of Norway and the French Ministry of Foreign Affairs. The participants belong to the following institutions: InriaSophia Antipolis (project-team Maestro; N. Bonneau contributed to this project) and Institut Eurecom, France, UniK - University Graduate Center and University of Oslo, Norway. The objective is to propose advanced optimization tools to design broadband wireless communication systems (OFDM, CDMA, MIMO, and ad hoc networks).

Maestrotogether with N. Litvak and W. Scheinhardt from the University of Twente, The Netherlands, is involved in the Pai Eco-Netin partnership with V. Dobrynin, L. Petrosyan, D. Nemirovsky and N. Osipova from St. Petersburg State University, Russia, and A. Dudin and V. Klimenok from Belarussian State University, Belarus. The collaboration, started in 2005, bears on ``Probabilistic and Graph Theoretical Methods in Search Engines.'' The collaboration has been extended for a second year (2006).

Members of Maestroand the University of Massachusetts ( UMass) at Amherst (Prof. D. Towsley) have a long lasting collaboration in the area of performance evaluation and control of networks. Since 2001, we have been associated with UMassin a five-year Nsf Itrproject on ``QoS in the future Internet''. This project finances visits of members of Maestroto UMass. In 2005 P. Nain visited UMassin this framework.

Since January 2004 Maestroand Inriaproject-team Oasishave been partners in a four-year collaboration with the University of Los Andes (ULA), Merida, Venezuela, through a funding of the Ecosprogram. French partners are D. Ros ( Inriaproject-team Armorand EnstBretagne), D. Caromel ( Inriaproject-team Oasis), H. Mounier (University of Paris 11, Orsay), and E. Altman (project coordinator). Our Venezuelian partners are R. Márquez, L. Leon and J. Aguilar from ULA (Merida). Within this project Maestrohosted R. Márquez for three weeks in 2005.

Members of Maestroare involved in two Aci(Incitative Coordinated Actions) sponsored by the Cnrs, Inria, the Ministry of Education and Research and other institutions.

One is the Fluxproject of the Aci``Masses of Data''. Its main topic is the use of probabilistic counting to devise lightweight algorithms for flow classification in networks.

The second one is the Sr2i(Security of Interdomain Routing in the Internet) of the Aci``Security in Informatics'', the topic of which is the reliability and security of the BGP routing protocol.

Urtzi Ayesta ( Cwi, Amsterdam, The Netherlands, 05/23/05–/06/05/05), Vladimir Dobrynin (St. Petersburg State University, Russia, 07/10/05–07/18/05), Evsey Morozov (Petrozavodsk State University, 09/16/06–09/18/05), Rudesindo Núñez Queija ( Cwi, Amsterdam, The Netherlands, 12/14/05–12/16/05), Leon Petrosjian (St. Petersburg State University, Russia, 07/15/05–07/28/05), Sergey Savchenko (Russian Academy of Science, Moscow, 04/03/05–04/17/05), Jorma Virtamo (Helsinki University of Technology, Finland, 10/01/05–10/06/05).

Bezalel Gavish (Southern Methodist Univ., Dallas, TX, USA, 05/01/05–05/06/05), Harold Kushner (Brown University, Providence, CI, USA, 09/12/05–09/16/05), Keith W. Ross (Polytehnic University, Brooklyn, NY, USA, 10/01/05–10/08/05), R. Srikant (University of Illinois at Urbana-Champaign, IL, USA, 10/02/05–10/05/05), Don Towsley (University of Massachusetts, MA, USA, 10/01/05–10/09/05).

Moshe Haviv (The Hebrew University of Jerusalem, Israël, 01/16/05–01/29/05), Uri Yechiali (University of Tel Aviv, Israel, 10/09/05–10/21/05).

Hisao Kameda (University of Tsukuba, Japan, 03/23/05–03/30/05), Vinod Sharma ( IIScBangalore, India, 10/10/05–01/10/06).

Vladimir Ejov (Univ. of South Australia, Adelaïde, Australia, 06/24/05–07/06/05), Jersy Filar (University of South Australia, Adelaïde, Australia, 03/21/05–04/03/05), Luke Finlay (University of South Australia, Adelaïde, Australia, 06/27/05–06/28/05), Vladimir Gaitsgory (Univ. of South Australia, Adelaïde, Australia, 06/23/05–06/28/05).

visited France Telecom R&D, Issy-les-Moulineaux, on February 15–16, 2005 and on June 21, 2005 within the framework of a two years contract with France Telecom R&Dwhich started in February 2005. On July 22-23, 2005 he visited Int(Institut National des Télécommunications) in Evry, France, for a collaboration with T. Chahed (as part of the CellularSpecific Joint Research Project of the Network of Excellence EuroNgi). E. Altman also participated in a meeting at Ensin Paris, with other members of the Cellular EuroNgiproject May 26–27, 2005, and he participed in a meeting in Milano, Italy, on February 8, 2005, for preparation of the IstEuropean BionetsIntegrated Project.

Cwi, Amsterdam (April 21–27, 2005), St. Petersburg State University, Russia (May 1–15, 2005), Belarussian State University, Belarus (December 23–31, 2005), and University of South Australia (November 1–30, 2005).

visited the Computer Science Laboratory of the EnsLyon (November, 24–25).

visited the Massachusetts Institute of Technology ( Mit), Boston, USA, (October 14–15, 2005) on a travel grant from Mit, Intin Evry, France (November 14–17, 2005), and École Normale Supérieure ( Ens) in Paris (November, 18 2005).

visited T. Basar and R. Srikant at University of Illinois, Urbana Champaign (May 2005), and R. Núñez Queija at Cwi, Amsterdam, The Netherlands (June 2005).

visited IitDelhi and IIScBangalore, India (July 30 – August 27, 2005) and France Telecom R&D, Issy les Moulineaux, France (June 21 and December 5–6, 2005). On June 21 he gave a presentation on ``Novel Channel Switching Policies for Packet Data Transmission in UMTS'' at France Telecom R&D, Issy les Moulineaux, France.

visited the Gerad, University of Montreal, Canada (May 9–May 28, 2005), and the Department of Applied Economics of the University of Valladolid (November 28–December 2, 2005).

visited the University of Massachussets at Amherst, USA for two weeks in June 2005, in the framework of the Nsf Itrproject on ``QoS in the future Internet''.

visited the University of St. Petersburg, Russia (August 19–31, 2005) in the framework of the Pai Eco-Netproject.

is an Associate Editor of the following journals:
*Journal of Economics, Dynamics and Control*(JEDC),
*Stochastic Models*,
*ACM/Kluwer Wireless Networks*(WINET),
*Communication Networks*(COMNET),
*SIAM Journal on Control and Optimization*(SICON), and
*Journal of Discrete Event Dynamic Systems*(JDEDS) (starting January 2006). In 2005 E. Altman was Guest Editor of the following journals:

*IEEE Journal on Selected Areas in Communications*(JSAC): ``Wireless Ad Hoc Networks – Part I,'' Eds: J. E. Wieselthier, E. Altman, A. Ephremides, J. P. Macker, H. B. Russell, M. Steenstrup, and S. B. Wicker, Vol. 23, Number 1, January 2005.

*IEEE Journal on Selected Areas in Communications*(JSAC): ``Wireless Ad Hoc Networks – Part II,'' Eds: J. E. Wieselthier, E. Altman, A. Ephremides, J. P. Macker, H. B. Russell, M. Steenstrup, and S. B. Wicker, Vol. 23, Number 3, March 2005.

*Telecommunication Systems*, Special Issue on ``High Speed Transport Protocols,'' Editors: S. Molnar and E. Altman, Volume 30, Issue 4, December 2005.

is an Associate Editor for
*RAIRO Operations Research*and
*Performance Evaluation*.

is an Associate Editor of
*Performance Evaluation*,
*Operations Research Letters*and
*IEEE/ACM Transactions on Networking*(starting January 2006).

was a program committee member of
*IEEE Infocom 2005*(Miami, FL, USA, March 13–17, 2005),
*Networking 2005*(Waterloo, Canada, May 2–6, 2005),
*11th European Wireless Conference*(Nicosia, Cyprus, April 10–13, 2005),
*WONS 2005 – The Second Annual Conference on Wireless On Demand Network Systems and Services*(St. Moritz, Switzerland, January 19–21, 2005),
*Int. Workshop on Protocols for Fast Long-Distance Networks*(PFLDNET – Lyon, France, February 3–4, 2005),
*Ad hoc Now'05 - 4th International Conference on AD-HOC Networks and Wireless*(Cancun, Mexico, October 6–9,2005),
*WiOpt'05 – Workshop on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks*(Riva del Garda, Trentino, Italy, April 3–7, 2005),
*IWQoS 2005 – 13th IEEE Int. Workshop on Quality of Service*(Pasau, Germany, June 21–23, 2005),
*WICON 2005 - First Int. Wireless Internet Conference*(Budapest, Hungary, July 10-14, 2005).

was a program committee member of the following conferences:
*Performance 2005*(Juan-les-Pins, France, October 3–7, 2005),
*MAMA 2005*(held in conjunction with Sigmetrics 2005),
*MASCOTS 2005*(Atlanta, GA, USA, September 27–29, 2005),
*Asian Internet Engineering Conference 2005*(AINTEC 2005 – Bangkok, Thailand, December 13-15),
*2nd European Performance Evaluation Workshop 2005*(EPEW 2005 – Versailles, France, September 1–3, 2005).

was a program committee member of
*ACM Sigmetrics 2005*(Banff, Canada, June 6-10, 2005) and
*MAMA 2005*(held in conjunction with Sigmetrics 2005).

was Publicity Chair and Webmaster of
*Performance 2005*(Juan-Les-Pins, October 3–7, 2005 –
http://www-sop.inria.fr/maestro/performance2005/).

was the General Chair of
*WiOpt'05*(Workshop on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks – Riva del Garda, Trentino, Italy, April 3-7, 2005), steering committee member of the conferences
*WiOpt'05*and
*ValueTools 2006*(Conf. on Performance Evaluation Methodologies and Tools – Pisa, Italy, October 2006), and Tutorial Co-Chair (with Z. Liu, IBM T.J. Watson) of
*Performance 2005*((Juan-Les-Pins, October 3–7, 2005).

organized and chaired the invited session on ``Searching and Ranking in Information Networks'' at
*INFORMS Applied Probability Conference*(Ottawa, Canada, July 6–8, 2005). He also organised and chaired the ``Work-in-Progress'' session at
*Performance 2005*(Juan-Les-Pins, October 3–7, 2005).

was Publicity Chair of
*WiOpt'05*(Workshop on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks – Riva del Garda, Trentino, Italy, April 3-7, 2005). She was also Arrangement Co-Chair (with D. Sergeant from
Inria) of
*Performance 2005*(Juan-Les-Pins, October 3–7, 2005),
*ICGT'05*(7th International Colloquium on Graph Theory, Hyères, France, September 12-16, 2005), and of the workshop ``JCB 60'' organized in Sophia Antipolis on December 8-9, 2005, to celebrate the 60th birthday of J.-C. Bermond.

co-organized and co-chaired (with J.-M. Fourneau, University of Versailles, France) the Ifip Wg7.3 workshop on October 8, 2005 in Juan-les-Pins, France.

was the General Chair of the
Ifip Wg7.3 24th International Symposium on Computer Performance, Modeling, Measurements and Evaluation (
*Performance 2005*), Juan-les-Pins, October 3-7, 2005.

participated as co-thesis advisor in the PhD thesis committee of Balakrishna Prabhu ( Unsa, 10/04/05).

participated as a reviewer in the HDR thesis committee of Tijani Chahed (University of Paris 6, 07/12/05) and in the PhD thesis committees of Patrick Maille ( Enst Bretagne, 07/11/05), Yezekael Hayel (University of Rennes 1, France, 12/9/05), Matthieu Jonckheere (Ecole Polytechnique, Palaiseau, France, 12/9/05). He participed as a co-advisor in the PhD thesis committee of Balakrishna Prabhu ( Unsa, France, 10/04/05).

participated as a reviewer in the PhD thesis committees of J. Orozco (University of Rennes 1, France, 04/04/05) and Martín Varela Rico (University of Rennes 1, France, 11/10/05).

participated as the thesis advisor in the PhD thesis committees of Patrick Brown ( Unsa, France, 12/15/05), Florence Clévenotrronin ( Unsa, France, 10/3/05), Robin Groenevelt ( Unsa, France, 04/07/05), and as a reviewer in the PhD thesis committee of Charles Bockstal (University Paul Sabatier, Toulouse, France, 11/04/05).

The following PhD theses were defended in 2005:

(advisor: P. Nain) on April 7, 2005 (committee members: R. Mazumdar and M. Mandjes, reviewers; J.-C. Bermond, G. Koole, I. Litovsky, P. Nain ).

(advisor: P. Nain) on October 3, 2005 (committee members: R. Srikant and D. Towsley, reviewers; E. Biersack, P. Nain, K. W. Ross, J.-M. Vincent).

(advisors: E. Altman and K. Avrachenkov) on October 4, 2005 (committee members: G. Koole and J. Virtamo, reviewers; E. Altman, K. Avrachenkov, T. Bonald, R. Srikant).

is head of the Apr(Algorithms and Performance of Networks) Project of the LirmmLaboratory of the University of Montpellier II.

is co-chair of the Department of Informatics of the LirmmLaboratory, Montpellier.

coordinated the curriculum of the Master Program in Computer Science, specialization in Research, at the University of Montpellier II, until September 2005.

is a member of the Specialists Committee (Commission de Spécialistes) in Computer Science at the University of Montpellier II.

acted as an expert for the Dga(Direction Générale de l'Armement).

acted as an expert for the Laas(Laboratoire d'Analyse et d'Architecture des Systèmes) of Toulouse.

is vice-chair of the Projects Committee of the InriaUnit Research of Sophia Antipolis (since September 1, 2005).

is a member of the Scientific Committee of Cnrt(Centre Nationaux de Recherche Technologiques) Telius(Telecom, Internet and Usage).

is in charge of the Master program on ``Networking and Distributed Systems'' at the University of Nice Sophia Antipolis (since the academic year 2000-2001).

is a member of the Advisory Board (and treasurer) of Ifip Wg7.3 (elected in 2002).

are (elected) members of Ifip Wg7.3 on ``Computer System Modeling''.

participated in the course on ``Communication and Networks'' of the Master in Computer Science of the University of Montpellier II (12H). She taught courses on the ``Quality of Service in Networks'' in the Master of the University of Montpellier II (14H), and a course on ``Random Models'' (21H).

taught courses at the University of Nice-Sophia Antipolis on Discrete Mathematics (48H), SAS Programming and Data Mining (24H), Game Theory (18H), and participed to the course on Numerical Programming at Essi(6H).

participated in the course on ``Dynamics and Algorithmics of Networks'' of the Master in Computer Science MPRI (Paris 6/ENS/École Polytechnique, 9H). He taught a course on Random Discrete Structures in the Master in Informatics of the University of Montpellier II (27H).

taught a course on NS-2 Network Simulator in the Master Program on ``Networks and Distributed Systems'' at the University of Nice Sophia Antipolis (15H).

taught a course on the Performance Evaluation of Networks in the Master Program on ``Networks and Distributed Systems'' at the University of Nice Sophia Antipolis (21H).

was a Keynote speaker at the
*MSO 2005 – Fifth IASTED International Conference on Modelling, Simulation and Optimization*(Oranjestad, Aruba, August 29–31, 2005).

attended (as an author of a paper)
*IEEE Infocom 2005*(Miami, FL, USA, March 13–16).

gave presentations at
*IEEE Infocom 2005*(Miami, FL, USA, March 13–17, 2005),
*INFORMS Applied Probability Conference*(Ottawa, Canada, July 6–8, 2005), Worshop on ``Optimal Stopping and Stochastic Control'' (Petrozavodsk, Russia, August 22–26, 2005), Workshop on Congestion Control at the Hamilton Institute (Ireland, September 27–28, 2005 – invited lecture),
*IEEE CDC/ECC 2005*(Seville, Spain, December 12–15, 2005).

gave presentations at
*ICASSP 2005 – IEEE International Conference on Acoustics, Speech and Signal Processing*(Philadelphia, PA, USA, March 18–23, 2005),
*ITC'19 – 19th International Teletraffic Congress*(Beijing, China, August 29–September 2, 2005),
*2005 IEEE International Symposium on Information Theory*(Adelaide, Australia, September 4–9, 2005),
*ISWCS 2005 – 2nd International Symposium on Wireless Communication Systems*(Siena, Italy, September 5–7, 2005).

gave lectures at
*Performance 2005*(Juan-les-Pins, France, October 3–7, 2005),
*IEEE 10th Int. Workshop on Web Content Caching and Distribution*(WCW 2005 – Sophia Antipolis, France, September 12–14 2005).

gave invited lectures at Institut National des Télécommunications (INT) in Evry, France (November 17, 2005), École Normale Supérieure, Paris (November 18, 2005), Institut Eurecom, Sophia Antipolis (8 December 2005), and France Telecom R&Din the framework of ``Cellular'' specific research project of the EuroNGI Network of Excellence – December 6, 2005).

gave lectures at
*IEEE Infocom 2005*(Miami, FL, USA, March 13–16) and at
*Performance 2005*(Juan-les-Pins, France, October 3–7, 2005), and presented a poster at
*ACM SIGMETRICS 2005*(Banff, Canada, June 6–10).

was an invited speaker at the Lunteren Conference (30th Conference on the Mathematics of Operations Research), The Netherlands, January 18–20, 2005. He gave a presentation at the Colloque International du 25e anniversaire du GERAD, Montreal, Canada, May 11–13, 2005. The paper was also presented at that workshop. The paper was presented to the Optimization Days, Montreal, Canada, May 9–11, 2005. Together with Bruno Gaujal ( Inriaproject-team Mescal), A. Jean-Marie taught course on Optimal Control and Balance Word at the EJC'O5: Ecole Jeunes Chercheurs en Algorithmique et Calcul Formel, Montpellier, April 2005.

gave lectures at
*WiOpt 2005*(Trento, Italy, April 3–7, 2005),
*IEEE Infocom 2005*(Miami, FL, USA, March 13–16) and
*IFIP Networking 2005*(Waterloo, Canada, May 2–6, 2005).

presented a paper at the
*19th International Teletraffic Congress*(ITC-19 –Beijing, China, August 29– September 2, 2005).

presented a paper at the
*19th International Teletraffic Congress*(ITC-19 –Beijing, China, August 29– September 2, 2005).

gave lectures at
*IEEE Infocom 2005*(Miami, FL, USA, March 13–16),
*Pfldnet 2005 – Third International Workshop on Protocols for Fast Long-Distance Networks*(Lyon, France, February 3–4, 2005),
*Mathematics 2005*(Liverpool, UK, April 4–7, 2005),
*Workshop on Optimal Stopping and Stochastic Control*(Petrozavodsk, Russia, August 22–26, 2005).