Seminar: Choosing amongst heterogeneous servers with applications to cloud computing by Ravi Mazumdar

Date: Wednesday the 8th of July,
Place: ENS de Lyon, Amphi B

Title: Choosing amongst heterogeneous servers with applications to cloud computing

Summary : Many cloud systems such as the Amazon EC2 provide resources for clients to use. These resources are shared between many tasks. A natural model is to use a processor sharing. In this talk I will discuss new advances in understanding good policies to choose amongst heterogeneous servers in order to obtain low latencies for job execution.

We will first discuss the so-called Power-of-two rule in the homogeneous case of identical servers where routing to the least occupied server amongst two randomly chosen servers results in a very low server occupancy and a so-called propagation of chaos or asymptotic independence. The hetero- geneous case has not been treated in the literature. In the heterogeneous case we will see that the stability region for randomized routing is strictly included in the maximal stability region that can be achieved by state independent routing. Therefore the average sojourn of tasks can be longer in randomized routing in heterogeneous systems. When the system is stable we completely character- ize the steady-state behavior of the server occupancies and show that it exhibits super-exponential decay and asymptotic independence among servers. To overcome the reduction in the stability region we show that a combination of state independent routing (biased sampling) to a server class combined with JSQ within the class recovers the stability region as well as the benefits of small server occupancies. We conclude with the situation when the server speeds at different clusters are not known

The techniques are based on a mean field analysis. Joint work with Arpan Mukhopadhyay (Waterloo).

Biography: The speaker was educated at the Indian Institute of Technology, Bombay (B.Tech, 1977), Imperial College, London (MSc, DIC, 1978) and obtained his PhD under A. V. Balakrishnan at UCLA in 1983.

He is currently a University Research Chair Professor in the Dept. of ECE at the University of Waterloo, Ont., Canada where he has been since September 2004. Prior to this he was Professor of ECE at Purdue University, West Lafayette, USA. Since 2012 he is a D.J. Gandhi Distinguished Visiting Professor at the Indian Institute of Technology, Bombay, India. He is a Fellow of the IEEE and the Royal Statistical Society. He is a recipient of the INFOCOM 2006 Best Paper Award and was runner-up for the Best Paper Award at INFOCOM 1998.

His research interests are in stochastic modelling and analysis applied to complex networks and systems and in issues of network science.

(Français) L’âme sœur

Sorry, this entry is only available in French.

Best demo/tutorial at Tridentcom2015

FIT IoT Lab and OneLab received the best demo award at TRIDENTCOM 2015, 10th EAI International Conference on Testbeds and Research Infrastructures for the Development of Networks & Communities,  Vancouver, Canada, June 24–25, 2015.


25th GRETSI will be in Lyon in Sept 2015.

Les présidents du comité d’organisation sont :

Paulo Gonçalves
INRIA, DR, ENS de Lyon, Laboratoire d’Informatique

Patrice Abry
CNRS, DR, ENS de Lyon, Laboratoire de Physique

Toutes les informations sur le site web du GRETSI 2015. 

(Français) Ecole d’été resCom : SmartCITIES

Sorry, this entry is only available in French.

ANR – REsilient and FLEXible Infrastructure for Open Networking: REFLEXION

The REFLEXION (REsilient and FLEXible Infrastructure for Open Networking) project, started in February 2015, is an industrial research project that leans on the complementary technical expertise of the partners to bring (i) robustness and flexibility in NFV-SDN architectures, in particular to support critical services, and (ii) dynamicity and efficiency for the provisioning and the chaining of virtualized network functions.

Partners are :

  • Thales Communications & Security
  • Orange
  • UPMC
  • 6WIND
  • ENSL
  • Telecom Paris Tech
  • Fore more informations:

    ANR – DIstributed SDN COntrollers: DISCO

    DISCO (DIstributed SDN COntrollers for rich and elastic network services) is an ANR funded project. It started on January 1st 2014 and it will last up to June 2017.

    DISCO proposes to explore the way how SDN changes network monitoring, control, urbanisation and abstract description of network resources for the optimisation of services. SDN promises a wide array of optimization techniques and newer algorithms for managing traffic.

    Partners are :

  • Thales Communications & Security
  • 6WIND
  • ENSL
  • Fore more informations:

    UCOOL meeting in Valparaiso

    Chile_2015 - 2437

    Seminar: Analysis of Large-scale systems: Information Theory & combinatorial optimisation

    Date:  lundi 20 avril 2015 à 14:00
    Lieu: Salle IXXI GN Nord 207
    Titre: Analyse multi-échelles des systèmes complexes : théorie de l’information et optimisation combinatoire

    Résumé :
    Entre causalités microscopiques et phénomènes émergents, l’analyse des systèmes complexes ne peut véritablement se passer d’une approche multi-échelles. Nous abordons en particulier deux problèmes : celui de la représentation (multi-échelles) de données structurées et celui de la prédiction (multi-échelles) des systèmes dynamiques. Premièrement, nous proposons d’exploiter des mesures classiques développées en théorie de l’information pour évaluer la pertinence des niveaux de représentation/prédiction en termes d’information et de complexité(gain d’entropie, divergence de Kullback-Leibler, Information Bottleneck). Le problème de la représentation/prédiction optimale est donc formalisé sous la forme d’un problème d’optimisation combinatoire à deux objectifs, visant à extraire et agréger l’information disponible au niveau microscopique pour apporter des éléments d’analyse macroscopique. Deuxièmement, afin d’engendrer des représentations exploitables en pratiques par les experts, nous garantissons leur cohérence avec les connaissances a priori du système en contraignant l’espace de recherche du problème d’optimisation à partir des propriétés structurelles du système. Si le problème d’optimisation correspondant est NP-complet en général, nous proposons néanmoins des algorithmes polynomiaux dans le cas de structures particulières (hiérarchies, ensembles d’intervalles, produit cartésien des deux structures). Cette approche est notamment appliquée à l’agrégation spatio-temporelle de données médiatiques pour l’analyse multi-échelles des relations internationales, et à la prédiction des dynamiques multi-échelles dans un modèle classique de diffusion d’opinion (Voter Model).

    Detailed Contact Data and the Dissemination of Staphylococcus aureus in Hospitals

    just released and at the head line of  Plos Comp Bio.


    Full version available online :