This document describes the Optimized Link State Routing (OLSR) protocol for mobile ad hoc networks. The protocol is an optimization of the classical link state algorithm tailored to the requirements of a mobile wireless LAN. The key concept used in the protocol is that of multipoint relays (MPRs). MPRs are selected nodes which forward broadcast messages during the flooding process. This technique substantially reduces the message overhead as compared to a classical flooding mechanism, where every node retransmits each message when it receives the first copy of the message. In OLSR, link state information is generated only by nodes elected as MPRs. Thus, a second optimization is achieved by minimizing the number of control messages flooded in the network. As a third optimization, an MPR node may chose to report only links between itself and its MPR selectors. Hence, as contrary to the classic link state algorithm, partial link state information is distributed in the network. This information is then used for route calculation. OLSR provides optimal routes (in terms of number of hops). The protocol is particularly suitable for large and dense networks as the technique of MPRs works well in this context.

https://hal.inria.fr/inria-00471712/document

Optimized Link State Routing Protocol (OLSR)

Networked sensors-those that coordinate amongst themselves to achieve a larger sensing task-will revolutionize information gathering and processing both in urban environments and in inhospitable terrain. The sheer numbers of these sensors and the expected dynamics in these environments present unique challenges in the design of unattended autonomous sensor networks. These challenges lead us to hypothesize that sensor network coordination applications may need to be structured differently from traditional network applications. In particular, we believe that localized algorithms (in which simple local node behavior achieves a desired global objective) may be necessary for sensor network coordination. In this paper, we describe localized algorithms, and then discuss directed diffusion, a simple communication model for describing localized algorithms.

https://www.cs.jhu.edu/~cs647/class-papers/Sensor%20Nets/estrin.pdf

Next century challenges: scalable coordination in sensor networks

Underwater sensor nodes will find applications in oceanographic data collection, pollution monitoring, offshore exploration, disaster prevention, assisted navigation and tactical surveillance applications. Moreover, unmanned or autonomous underwater vehicles (UUVs, AUVs), equipped with sensors, will enable the exploration of natural undersea resources and gathering of scientific data in collaborative monitoring missions. Underwater acoustic networking is the enabling technology for these applications. Underwater networks consist of a variable number of sensors and vehicles that are deployed to perform collaborative monitoring tasks over a given area. In this paper, several fundamental key aspects of underwater acoustic communications are investigated. Different architectures for two-dimensional and three-dimensional underwater sensor networks are discussed, and the characteristics of the underwater channel are detailed. The main challenges for the development of efficient networking solutions posed by the underwater environment are detailed and a cross-layer approach to the integration of all communication functionalities is suggested. Furthermore, open research issues are discussed and possible solution approaches are outlined. � 2005 Published by Elsevier B.V.

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Underwater acoustic sensor networks: research challenges

Ad hoc networks are a new wireless networking paradigm for mobile hosts. Unlike traditional mobile wireless networks, ad hoc networks do not rely on any fixed infrastructure. Instead, hosts rely on each other to keep the network connected. Military tactical and other security-sensitive operations are still the main applications of ad hoc networks, although there is a trend to adopt ad hoc networks for commercial uses due to their unique properties. One main challenge in the design of these networks is their vulnerability to security attacks. In this article, we study the threats on ad hoc network faces and the security goals to be achieved. We identify the new challenges and opportunities posed by this new networking environment and explore new approaches to secure its communication. In particular, we take advantage of the inherent redundancy in ad hoc networks-multiple routes between nodes-to defend routing against denial-of-service attacks. We also use replication and new cryptographic schemes, such as threshold cryptography, to build a highly secure and highly available key management service, which terms the core of our security framework.

/pdf/securing-ad-hoc-networks-3hudjv4io2.pdf

Securing ad hoc networks

The theory of directed graphs has developed enormously over recent decades, yet this book (first published in 2000) remains the only book to cover more than a small fraction of the results. New research in the field has made a second edition a necessity. Substantially revised, reorganised and updated, the book now comprises eighteen chapters, carefully arranged in a straightforward and logical manner, with many new results and open problems. As well as covering the theoretical aspects of the subject, with detailed proofs of many important results, the authors present a number of algorithms, and whole chapters are devoted to topics such as branchings, feedback arc and vertex sets, connectivity augmentations, sparse subdigraphs with prescribed connectivity, and also packing, covering and decompositions of digraphs. Throughout the book, there is a strong focus on applications which include quantum mechanics, bioinformatics, embedded computing, and the travelling salesman problem. Detailed indices and topic-oriented chapters ease navigation, and more than 650 exercises, 170 figures and 150 open problems are included to help immerse the reader in all aspects of the subject. Digraphs is an essential, comprehensive reference for undergraduate and graduate students, and researchers in mathematics, operations research and computer science. It will also prove invaluable to specialists in related areas, such as meteorology, physics and computational biology.

Digraphs Theory Algorithms And Applications

A peer-to-peer file sharing system includes a lookup and a content distribution protocol. Very efficient peer-to-peer protocols exist for content distribution, but efficient indexing is still an open problem. Numerous work on structured overlay networks such as distributed hash tables offer a promising framework. However, balancing the load of publishing, storing indexes and answering request still remains a challenging task. We sketch a general architecture framework for solving these problems in the case of a file sharing application. Our design goals include reducing the work of file providers (they should not bare all the publishing process) and enabling keyword searching based on the assumption that few words are associated with each file.

/pdf/optimizing-and-balancing-load-in-fully-distributed-p2p-file-311ampkiu3.pdf

Optimizing and Balancing Load in Fully Distributed P2P File Sharing Systems

Ce papier s'interesse aux liens entre deux concepts : d'une part le clustering de graphes, mesure par la modularite de Newman, et d'autre part le clustering d'un espace metrique, mesure par la somme des carres des distances au barycentre des clusters. Nous montrons qu'en passant de l'espace a un graphe de facon ''naturelle'' (par boules unitaires) et en appliquant un algorithme ''naturel'' de clustering (par r-net), on obtient un clustering de modularite bornee inferieurement (en fonction de la dimension de grille de l'espace et pour certains rayons de r-net). Quelques simulations en espace euclidien viennent illustrer le propos en comparant deux algorithmes pour les deux mesures de qualite.

https://hal.inria.fr/inria-00583844/document

Clustering de métrique et clustering de graphe

We consider the problem of collaborative tree exploration posed by Fraigniaud, Gasieniec, Kowalski, and Pelc [Fraigniaud et al., 2006] where a team of k agents is tasked to collectively go through all the edges of an unknown tree as fast as possible. Denoting by n the total number of nodes and by D the tree depth, the O ( n/ log( k ) + D ) algorithm of Fraigniaud et al. [2006] achieves the best-known competitive ratio with respect to the cost of oﬄine exploration which is Θ(max { 2 n/k, 2 D } ) . Brass, Cabrera-Mora, Gasparri, and Xiao Brass et al. [2011] consider an alternative performance criterion, namely the additive overhead with respect to 2 n/k , and obtain a 2 n/k + O (( D + k ) k ) runtime guarantee. In this paper, we introduce ‘Breadth-First Depth-Next’ (BFDN), a novel and simple algorithm that performs collaborative tree exploration in time 2 n/k + O ( D 2 log( k )) , thus outperforming Brass et al. [2011] for all values of ( n, D ) and being order-optimal for all trees with depth D = o k ( √ n ) . Moreover, a recent result from Disser et al. [2017] implies that no exploration algorithm can achieve a 2 n/k + O ( D 2 − (cid:15) ) runtime guarantee. The dependency in D 2 of our bound is in this sense optimal. The proof of our result crucially relies on the analysis of an associated two-player game. We extend the guarantees of BFDN to: scenarios with limited memory and communication, adversarial setups where robots can be blocked, and exploration of classes of non-tree graphs. Finally, we provide a recursive version of BFDN with a runtime of O (cid:96) ( n/k 1 /(cid:96)

Breadth-First Depth-Next: Optimal Collaborative Exploration of Trees with Low Diameter

The problem of detecting loops in a forwarding network is known to be NP-complete when general rules such as wildcard expressions are used. Yet, network analyzer tools such as Netplumber (Kazemian et al., NSDI'13) or Veriflow (Khurshid et al., NSDI'13) efficiently solve this problem in networks with thousands of forwarding rules. In this paper, we complement such experimental validation of practical heuristics with the first provably efficient algorithm in the context of general rules. Our main tool is a canonical representation of the atoms (i.e. the minimal non-empty sets) of the field of sets generated by a collection of sets. This tool is particularly suited when the intersection of two sets can be efficiently computed and represented. In the case of forwarding networks, each forwarding rule is associated with the set of packet headers it matches. The atoms then correspond to classes of headers with same behavior in the network. We propose an algorithm for atom computation and provide the first polynomial time algorithm for loop detection in terms of number of classes (which can be exponential in general). This contrasts with previous methods that can be exponential, even in simple cases with linear number of classes. Second, we introduce a notion of network dimension captured by the overlapping degree of forwarding rules. The values of this measure appear to be very low in practice and constant overlapping degree ensures polynomial number of header classes. Forwarding loop detection is thus polynomial in forwarding networks with constant overlapping degree.

https://hal.inria.fr/hal-01868778/document

Efficient Loop Detection in Forwarding Networks and Representing Atoms in a Field of Sets

Verifier des tables de routage consiste a tester la validite des tables de l'ensemble des routeurs d'un reseau donne. Par exemple, il peut s'agir de tester l'absence de boucle ou de trou noir. Dans cet article, nous proposons une approche en deux etapes : construire un ensemble representatif d'en-tetes de paquets, puis tester les proprietes desirees sur ces en-tetes. Toute la difficulte est de construire un ensemble relativement petit tout en garantissant qu'un paquet avec un en-tete arbitraire va se comporter exactement comme au moins l'un des en-tetes de l'ensemble representatif.

A partir d'un modele tres general inspire du paradigme Software Defined Networking (SDN), nous montrons que le probleme de la detection de boucles peut se resoudre en temps polynomial en la taille d'un ensemble representatif. Nous montrons aussi qu'une condition naturelle sur les regles de routage, inspiree des travaux de Boutier et Chroboczek sur le routage par source et destination, permet de construire un ensemble representatif dont la taille est au plus le nombre de regles de routage plus un. Par comparaison, sans cette condition naturelle, la taille de l'ensemble representatif peut dans le pire des cas etre exponentielle en la taille des en-tetes.

https://hal.inria.fr/hal-01148595/document

Laurent Viennot

Papers

Optimizing and Balancing Load in Fully Distributed P2P File Sharing Systems

Clustering de métrique et clustering de graphe

Breadth-First Depth-Next: Optimal Collaborative Exploration of Trees with Low Diameter

Efficient Loop Detection in Forwarding Networks and Representing Atoms in a Field of Sets

Vérification de tables de routage par utilisation d'un ensemble représentatif d'en-têtes