State machine replication (SMR) is a software technique for tolerating failures using commodity hardware. The critical service to be made fault-tolerant is modeled by a state machine. Several, possibly different, copies of the state machine are then deployed on different nodes. Clients of the service access the replicas through a SMR protocol which ensures that, despite concurrency and failures, replicas perform client requests in the same order. Two objectives underly the design and implementation of a SMR protocol: robustness and performance. Robustness conveys the ability to ensure availability (liveness) and one-copy semantics (safety) despite failures and asynchrony. On the other hand, performance measures the time it takes to respond to a request (latency) and the number of requests that can be processed per time unit (throughput). In this thesis, we present two contributions to state machine replication. The first contri- bution is LCR, a uniform total order broadcast (UTO-broadcast) protocol that is throughput optimal in failure-free periods. LCR can be used to totally order the requests received by a replicated state machine. LCR has been designed for small clusters of homogeneous machines interconnected by a local area network. It relies on a perfect failure detector and tolerates the crash failures of all but one replicas. It is based on a ring topology and only relies on point-to-point inter-process communication. We benchmark an implementation of LCR against two of the most widely used group communication packages and show that LCR provides higher throughput than them, over a large number of setups. The second contribution is Abstract, a new abstraction to simplify the design, proof and implementation of SMR protocols. Abstract focuses on the most robust class of SMR protocols, i.e. those tolerating arbitrary (client and replica) failures. Such protocols are called Byzantine Fault Tolerant (BFT) protocols. We treat a BFT protocol as a composition of instances of our abstraction. Each instance is developed and analyzed independently. To illustrate our approach, we first show how, with our abstraction, the benefits of a BFT protocol like Zyzzyva could have been developed using less than 24% of the actual code of Zyzzyva. We then present Aliph, a new BFT protocol that outperforms previous BFT protocols both in terms of latency (by up to 30%) and throughput (by up to 360%).

Texte remanié de: Doctoral thesis--University of London, 1997. / Bibliogr. p. 135-151.

Texte remanié de: Diss.--Fakultät für Geschichtswissenschaft--Bochum--Ruhr-Universität, 2000. Titre de soutenance : Kaiserzeitliche und frühbyzantinische Gebrauchskeramik des Milet Survey. Texte augmenté de: Magisterarbeit--Fakultät für Geschichtswissenschaft--Bochum--Ruhr-Universität, 2000. Titre de soutenance : Terra-Sigillata-Funde aus dem Survey der milesischen Halbinsel. / Résumé en anglais. Bibliogr. p. 355-359.

Texte remanié de: Thèse de Doctorat--Institut d'archéologie Vasile Pârvan de l'académie roumaine, Bucarest, 2008. / Notes bibliogr.

Thesis--University of Helsinki, 1997. / Includes bibliographical references (p. 409-426) and indexes.

Texte remanié de: Th. 3e cycle--Paris 1, 1983. / Nom d'éditeur et titre de collection translittérés du grec. Bibliogr. p. 187-196. Index.

Th. 3e cycle--Institut d'art et d'archéologie--Paris 1, 1971. / Mention parallèle de titre ou de responsabilité : 'Oi toihografies tou 'Osiou Louka : ta dutika parekklēsia / Theanō Hatzēdakē-Mpahara ; prol., André Grrabar. Notice translittérée du grec selon ISO R/843 (1968). Bibliogr. p. 189-199. Index.

Dans ce travail de thèse nous avons mené une recherche ciblée sur les fortifications de Cyrrhus. La problématique générale de cette recherche est d'identifier et de dater les différentes phases d'occupation, mais aussi de restituer le tracé de chaque phase de construction et d'analyser son évolution en fonction de la topographie. À partir des résultats obtenus sur le terrain, nous avons poursuivi certaines problématiques : tout d'abord, réexaminer la fondation des fortifications en appareil polygonal, c'est-à-dire les premières fortifications de la ville ; ensuite lier cette fondation à celle de la ville pour savoir si les deux sont contemporaines ou s'il y a eu deux phases successives dans le développement de la première occupation. Pour appuyer certaines hypothèses de datation de ces fortifications d'origine, notre étude s'est concentrée sur les caractéristiques et les concepts de la construction des fortifications d'origine, sur leur implantation topographique, leurs différentes composantes et, finalement, sur leurs matériaux et leurs techniques de construction, afin de savoir si elles ont été fondées selon une tradition connue dans d'autres fondations hellénistiques. Par la suite nous avons tenté d'apporter plus de données sur l'occupation de ces fortifications d'origine pendant les périodes romaine et byzantine, surtout la reconstruction de l'enceinte par Justinien au VIe siècle. / In this thesis we conducted a targeted search on the fortifications of Cyrrhus. The general problem of this research is to identify and date the different phases of occupation, but also to restore the layout of each construction phase and analyze its evolution according to the topography. From the results obtained in the field, we continued some issues: First, review the foundation of polygonal masonry fortifications, that is to say the first fortifications of the city; then link to that this foundation of the city to see if the two are contemporary or there were two phases in the development of the first occupation. To support some dating assumptions of these original I fortifications, our study focused on the characteristics and concepts of the construction of these original fortifications, their topographic location, their different components and, ultimately, their materials and their construction techniques, to see if they were founded on a tradition known in other Hellenistic foundations. Afterwards we tried to bring more data on the occupation of the original fortifications during the Roman and Byzantine periods, throughout their reconstruction by Justinian in the sixth century.

Ridefinizione del tema delle origini dei Goti secondo il recente dibattito e indagine storico-prosopografica basata su fonti narrative, documentarie, archeologiche ed epigrafiche sulla fisionomia identitaria e sociale degli Ostrogoti insediati in Italia e sopravvissuti nel periodo successivo alla Guerra Greco-Gotica (dalla seconda metà del VI sec. d.C..), con particolare attenzione alle aree di dominio bizantino. Il lascito della loro memoria etnica, storica e istituzionale nel Regnum longobardo e in alcune fonti narrative italiane medievali. / Redefinition of the Goths-origins them in the recent debate, and historical -prosopographical research based on narrative, documentary, archaeological and epigraphic sources about the identity and social make-up of living and surviving Ostrogoths in Italy after the Greek-Gothic War (from 2nd half of VIth century), particularly for the areas under Byzantine rule. The heritage of their ethnic, historical, and institutional remembrance in the Lombard kingdom and in some Italian middle-age narrative sources.

A mesure que les réseaux s'étendent, ils deviennent de plus en plus susceptibles de défaillir. En effet, leurs nœuds peuvent être sujets à des attaques, pannes, corruptions de mémoire... Afin d'englober tous les types de fautes possibles, nous considérons le modèle le plus général possible : le modèle Byzantin, où les nœuds fautifs ont un comportement arbitraire (et donc, potentiellement malveillant). De telles fautes sont extrêmement dangereuses : un seul nœud Byzantin, s'il n'est pas neutralisé, peut déstabiliser l'intégralité du réseau.Nous considérons le problème d'échanger fiablement des informations dans un réseau multi-Sauts malgré la présence de telles fautes Byzantines. Des solutions existent mais nécessitent un réseau dense, avec un grand nombre de voisins par nœud. Dans cette thèse, nous proposons des solutions pour les réseaux faiblement connectés, tels que la grille, où chaque nœud a au plus 4 voisins. Dans une première partie, nous acceptons l'idée qu'une minorité de nœuds corrects échouent à communiquer fiablement. En contrepartie, nous proposons des solutions qui tolèrent un grand nombre de fautes Byzantines dans les réseaux faiblement connectés. Dans une seconde partie, nous proposons des algorithmes qui garantissent une communication fiable entre tous les nœuds corrects, pourvu que les nœuds Byzantins soient suffisamment distants. Enfin, nous généralisons des résultats existants à de nouveaux contextes : les réseaux dynamiques, et les réseaux de taille non-Bornée. / As modern networks grow larger and larger, they become more likely to fail. Indeed, their nodes can be subject to attacks, failures, memory corruptions... In order to encompass all possible types of failures, we consider the most general model of failure: the Byzantine model, where the failing nodes have an arbitrary (and thus, potentially malicious) behavior. Such failures are extremely dangerous, as one single Byzantine node, if not neutralized, can potentially lie to the entire network. We consider the problem of reliably exchanging information in a multihop network despite such Byzantine failures. Solutions exist but require a dense network, where each node has a large number of neighbors. In this thesis, we propose solutions for sparse networks, such as the grid, where each node has at most 4 neighbors. In a first part, we accept that some correct nodes fail to communicate reliably. In exchange, we propose quantitative solutions that tolerate a large number of Byzantine failures, and significantly outperform previous solutions in sparse networks. In a second part, we propose algorithms that ensure reliable communication between all correct nodes, provided that the Byzantine nodes are sufficiently distant from each other. At last, we generalize existing results to new contexts: dynamic networks, and networks with an unbounded diameter.