Vers une utilisation de la diversité de chemins dans l'internet

In this thesis we consider a new service where carriers offer additional routes to their customers (w.r.t. to the BGP default route) as a free or value-added service. These alternate routes can be used by customers to optimize their communications, by bypassing some congested points in the Internet (e.g. a “tussled” peeringpoints), to help them to meet their traffic engineering objectives (better delays etc.) or just for robustness purposes (e.g, shift to a disjoint alternate route if needed). First we propose a simple architecture that allows a network service provider to benefit from the diversity it currently receives. Then we extend this architecture in order to make the propagation of the Internet path diversity possible, not only to direct neighbors but also to their neighbors and so on. We take advantage of this advance to relax the route selection processes of autonomous systems in order to make them be able to set up new routing paradigms. Nevertheless announcing additional paths can lead to scalability issues, so each carrier could receive more paths than what it could manage. We quantify this issue and we underline easy adaptations and small path filterings which make the number of paths drop to a manageable amount. Last but not least we set up an auction-type route allocation framework, which gives to network service providers the opportunities first to propagate to their neighbors only the paths the said neighbors are interested in and second to leverage a new routing selection paradigm based on commercial agreements and negotiationsNous considérons, dans cette thèse, un nouveau service par lequel les opérateurs de télécommunications offrent des routes supplémentaires à leurs clients (en plus de la route par défaut) comme un service gratuit ou à valeur ajoutée. Ces routes supplémentaires peuvent être utilisées par des clients afin d’optimiser leurs communications, en outrepassant des points de congestion d’Internet, ou les aider à atteindre leurs objectifs d’ingénierie de trafic (meilleurs délais etc.) ou dans un but de robustesse. Nous proposons d’abord une architecture simple permettant à un opérateur de télécommunication de bénéficier de la diversité de chemin qu’il reçoit déjà. Nous étendons ensuite cette architecture afin de rendre possible la propagation de cette diversité de chemin, non seulement aux voisins directs mais aussi, de proche en proche, aux autres domaines. Nous profitons de cette occasion pour relaxer la sélection des routes des différents domaines afin de leur permettre de mettre en place de nouveaux paradigmes de routage. Néanmoins, annoncer des chemins additionnels peut entrainer des problèmes de passage à l’échelle car chaque opérateur peut potentiellement recevoir plus de chemins que ce qu’il peut gérer. Nous quantifions ce problème et mettons en avant des modifications et filtrages simples permettant de réduire ce nombre à un niveau acceptable. En dernier, nous proposons un processus, inspiré des ventes aux enchères, permettant aux opérateurs de propager aux domaines voisins seulement les chemins qui intéressent les dits voisins. De plus, ce processus permet de mettre en avant un nouveau paradigme de propagation de routes, basé sur des négociations et accords commerciau

Enabling inter-domain path diversity

Nous considérons, dans cette thèse, un nouveau service par lequel les opérateurs de télécommunications offrent des routes supplémentaires à leurs clients (en plus de la route par défaut) comme un service gratuit ou à valeur ajoutée. Ces routes supplémentaires peuvent être utilisées par des clients afin d’optimiser leurs communications, en outrepassant des points de congestion d’Internet, ou les aider à atteindre leurs objectifs d’ingénierie de trafic (meilleurs délais etc.) ou dans un but de robustesse. Nous proposons d’abord une architecture simple permettant à un opérateur de télécommunication de bénéficier de la diversité de chemin qu’il reçoit déjà. Nous étendons ensuite cette architecture afin de rendre possible la propagation de cette diversité de chemin, non seulement aux voisins directs mais aussi, de proche en proche, aux autres domaines. Nous profitons de cette occasion pour relaxer la sélection des routes des différents domaines afin de leur permettre de mettre en place de nouveaux paradigmes de routage. Néanmoins, annoncer des chemins additionnels peut entrainer des problèmes de passage à l’échelle car chaque opérateur peut potentiellement recevoir plus de chemins que ce qu’il peut gérer. Nous quantifions ce problème et mettons en avant des modifications et filtrages simples permettant de réduire ce nombre à un niveau acceptable. En dernier, nous proposons un processus, inspiré des ventes aux enchères, permettant aux opérateurs de propager aux domaines voisins seulement les chemins qui intéressent les dits voisins. De plus, ce processus permet de mettre en avant un nouveau paradigme de propagation de routes, basé sur des négociations et accords commerciauxIn this thesis we consider a new service where carriers offer additional routes to their customers (w.r.t. to the BGP default route) as a free or value-added service. These alternate routes can be used by customers to optimize their communications, by bypassing some congested points in the Internet (e.g. a “tussled” peeringpoints), to help them to meet their traffic engineering objectives (better delays etc.) or just for robustness purposes (e.g, shift to a disjoint alternate route if needed). First we propose a simple architecture that allows a network service provider to benefit from the diversity it currently receives. Then we extend this architecture in order to make the propagation of the Internet path diversity possible, not only to direct neighbors but also to their neighbors and so on. We take advantage of this advance to relax the route selection processes of autonomous systems in order to make them be able to set up new routing paradigms. Nevertheless announcing additional paths can lead to scalability issues, so each carrier could receive more paths than what it could manage. We quantify this issue and we underline easy adaptations and small path filterings which make the number of paths drop to a manageable amount. Last but not least we set up an auction-type route allocation framework, which gives to network service providers the opportunities first to propagate to their neighbors only the paths the said neighbors are interested in and second to leverage a new routing selection paradigm based on commercial agreements and negotiation

Internet routing diversity for stub networks with a Map-and-Encap scheme

International audienceRouting diversity has been identified as essential for network robustness and traffic engineering. The Internet possesses by its very nature a large path diversity. However this diversity cannot be fully exploited due to BGP limitations, which only keeps one single route for each available prefix. Despite some previous works in the area, no operational and non-disruptive architecture have been proposed yet to allow the networks to better exploit Internet path diversity.This paper proposes one step in this direction, focusing on the interconnection between an Autonomous System (AS) and its Internet Service Provider (ISP). We propose the use of a so-called “Map-and-Encap” scheme to bypass current BGP limitations in order to use arbitrary paths. With this scheme, an ISP may propose its rich path diversity (at least partially) to its customers, in order to perform advanced traffic engineering (e.g. fast recovery, load balancing...) based on richer and more flexible path selection policies (e.g., considering price, performance or stability of routes). To assess the potential benefits of the proposed architecture, we evaluate the potential route diversity that a Tier 1 may offer to its stub clients, based on different possible route selection policies (i.e. which routes are offered to its customers). We also analyze the overhead that is created at the control-plane (routing updates received by the mapping database) and that may impact the data-plane (path changes that may be caused by some route withdrawals/updates). Our evaluation shows that the increase in diversity has a controllable and acceptable overhead. It also gives some insights into efficient deployment strategies

Inter-Domain Route Diversity for the Internet

Part 2: Economics and Technologies for Inter-Carrier ServicesInternational audienceThe current inter-domain routing in the Internet, which is based on BGP-4, does not allow for the use of multiple paths, but rather restricts the routing to a single path for each destination prefix. This fact is especially unfortunate considering the vast route diversity which is inherently present in the global Internet graph. Therefore, we propose Inter-Domain Route Diversity (IDRD) as an overlay mechanism which enables efficient, backwards compatible and incrementally deployable introduction of route diversity in the Internet. Beyond presenting the architecture of IDRD, this paper also presents the conditions which ensure the stability of the proposed mechanism as a fundamental prerequisite for its deployment in real-world scenarios

Auction-type framework for selling inter-domain paths

In the present Internet, inter-domain routing is based on BGP-4 [1] which selects a single path per destination prefix, thereby preventing carriers and end-users to use the vast inherent path diversity [2]. Addition of multi-path capabilities to the Internet have long been advocated for both robustness and traffic engineering purposes. Some works [3], [4] propose inter-domain multipath architectures. In this paper we consider a new service where carriers offer additional routes to their customers (w.r.t. to BGP default route) as an added-value service. These alternate routes can be used by customers to help them to meet their traffic engineering objectives (better delays etc.) or just for robustness purposes (disjoint alternate routes). Announcing additional paths can lead to scalability issues [5], so one carrier will propagate only the paths that are most interesting for neighboring domains. We propose an auction-like framework adapted to this specific service, allowing one carrier to select the most interesting paths and determine the prices at which these routes can be sold. We consider the case where routes are sold as infinitely duplicable goods (assuming small demands with regards to route capacities). We design a winner determination mechanism, based on the maximization of the seller's revenue, that enforces fair allocation of goods and is loser collusion proof. We also propose a payment mechanism that is proven to be truthful when each bidder submits one (potentially combinatorial) bid

Epidemiology of intra-abdominal infection and sepsis in critically ill patients: "AbSeS", a multinational observational cohort study and ESICM Trials Group Project

PURPOSE: To describe the epidemiology of intra-abdominal infection in an international cohort of ICU patients according to a new system that classifies cases according to setting of infection acquisition (community-acquired, early onset hospital-acquired, and late-onset hospital-acquired), anatomical disruption (absent or present with localized or diffuse peritonitis), and severity of disease expression (infection, sepsis, and septic shock). METHODS: We performed a multicenter (n = 309), observational, epidemiological study including adult ICU patients diagnosed with intra-abdominal infection. Risk factors for mortality were assessed by logistic regression analysis. RESULTS: The cohort included 2621 patients. Setting of infection acquisition was community-acquired in 31.6%, early onset hospital-acquired in 25%, and late-onset hospital-acquired in 43.4% of patients. Overall prevalence of antimicrobial resistance was 26.3% and difficult-to-treat resistant Gram-negative bacteria 4.3%, with great variation according to geographic region. No difference in prevalence of antimicrobial resistance was observed according to setting of infection acquisition. Overall mortality was 29.1%. Independent risk factors for mortality included late-onset hospital-acquired infection, diffuse peritonitis, sepsis, septic shock, older age, malnutrition, liver failure, congestive heart failure, antimicrobial resistance (either methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, extended-spectrum beta-lactamase-producing Gram-negative bacteria, or carbapenem-resistant Gram-negative bacteria) and source control failure evidenced by either the need for surgical revision or persistent inflammation. CONCLUSION: This multinational, heterogeneous cohort of ICU patients with intra-abdominal infection revealed that setting of infection acquisition, anatomical disruption, and severity of disease expression are disease-specific phenotypic characteristics associated with outcome, irrespective of the type of infection. Antimicrobial resistance is equally common in community-acquired as in hospital-acquired infection.status: publishe

Antimicrobial Lessons From a Large Observational Cohort on Intra-abdominal Infections in Intensive Care Units

evere intra-abdominal infection commonly requires intensive care. Mortality is high and is mainly determined by disease-specific characteristics, i.e. setting of infection onset, anatomical barrier disruption, and severity of disease expression. Recent observations revealed that antimicrobial resistance appears equally common in community-acquired and late-onset hospital-acquired infection. This challenges basic principles in anti-infective therapy guidelines, including the paradigm that pathogens involved in community-acquired infection are covered by standard empiric antimicrobial regimens, and second, the concept of nosocomial acquisition as the main driver for resistance involvement. In this study, we report on resistance profiles of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus faecalis and Enterococcus faecium in distinct European geographic regions based on an observational cohort study on intra-abdominal infections in intensive care unit (ICU) patients. Resistance against aminopenicillins, fluoroquinolones, and third-generation cephalosporins in E. coli, K. pneumoniae and P. aeruginosa is problematic, as is carbapenem-resistance in the latter pathogen. For E. coli and K. pneumoniae, resistance is mainly an issue in Central Europe, Eastern and South-East Europe, and Southern Europe, while resistance in P. aeruginosa is additionally problematic in Western Europe. Vancomycin-resistance in E. faecalis is of lesser concern but requires vigilance in E. faecium in Central and Eastern and South-East Europe. In the subcohort of patients with secondary peritonitis presenting with either sepsis or septic shock, the appropriateness of empiric antimicrobial therapy was not associated with mortality. In contrast, failure of source control was strongly associated with mortality. The relevance of these new insights for future recommendations regarding empiric antimicrobial therapy in intra-abdominal infections is discussed.Severe intra-abdominal infection commonly requires intensive care. Mortality is high and is mainly determined by diseasespecific characteristics, i.e. setting of infection onset, anatomical barrier disruption, and severity of disease expression. Recent observations revealed that antimicrobial resistance appears equally common in community-acquired and late-onset hospital-acquired infection. This challenges basic principles in anti-infective therapy guidelines, including the paradigm that pathogens involved in community-acquired infection are covered by standard empiric antimicrobial regimens, and second, the concept of nosocomial acquisition as the main driver for resistance involvement. In this study, we report on resistance profiles of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus faecalis and Enterococcus faecium in distinct European geographic regions based on an observational cohort study on intra-abdominal infections in intensive care unit (ICU) patients. Resistance against aminopenicillins, fluoroquinolones, and third-generation cephalosporins in E. coli, K. pneumoniae and P. aeruginosa is problematic, as is carbapenem-resistance in the latter pathogen. For E. coli and K. pneumoniae, resistance is mainly an issue in Central Europe, Eastern and South-East Europe, and Southern Europe, while resistance in P. aeruginosa is additionally problematic in Western Europe. Vancomycin-resistance in E. faecalis is of lesser concern but requires vigilance in E. faecium in Central and Eastern and South-East Europe. In the subcohort of patients with secondary peritonitis presenting with either sepsis or septic shock, the appropriateness of empiric antimicrobial therapy was not associated with mortality. In contrast, failure of source control was strongly associated with mortality. The relevance of these new insights for future recommendations regarding empiric antimicrobial therapy in intra-abdominal infections is discussed

Epidemiology of intra-abdominal infection and sepsis in critically ill patients: "AbSeS", a multinational observational cohort study and ESICM Trials Group Project

Purpose To describe the epidemiology of intra-abdominal infection in an international cohort of ICU patients according to a new system that classifies cases according to setting of infection acquisition (community-acquired, early onset hospital-acquired, and late-onset hospital-acquired), anatomical disruption (absent or present with localized or diffuse peritonitis), and severity of disease expression (infection, sepsis, and septic shock). Methods We performed a multicenter (n = 309), observational, epidemiological study including adult ICU patients diagnosed with intra-abdominal infection. Risk factors for mortality were assessed by logistic regression analysis. Results The cohort included 2621 patients. Setting of infection acquisition was community-acquired in 31.6%, early onset hospital-acquired in 25%, and late-onset hospital-acquired in 43.4% of patients. Overall prevalence of antimicrobial resistance was 26.3% and difficult-to-treat resistant Gram-negative bacteria 4.3%, with great variation according to geographic region. No difference in prevalence of antimicrobial resistance was observed according to setting of infection acquisition. Overall mortality was 29.1%. Independent risk factors for mortality included late-onset hospital-acquired infection, diffuse peritonitis, sepsis, septic shock, older age, malnutrition, liver failure, congestive heart failure, antimicrobial resistance (either methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, extended-spectrum beta-lactamase-producing Gram-negative bacteria, or carbapenem-resistant Gram-negative bacteria) and source control failure evidenced by either the need for surgical revision or persistent inflammation. Conclusion This multinational, heterogeneous cohort of ICU patients with intra-abdominal infection revealed that setting of infection acquisition, anatomical disruption, and severity of disease expression are disease-specific phenotypic characteristics associated with outcome, irrespective of the type of infection. Antimicrobial resistance is equally common in community-acquired as in hospital-acquired infection

Poor timing and failure of source control are risk factors for mortality in critically ill patients with secondary peritonitis

Purpose: To describe data on epidemiology, microbiology, clinical characteristics and outcome of adult patients admitted in the intensive care unit (ICU) with secondary peritonitis, with special emphasis on antimicrobial therapy and source control. Methods: Post hoc analysis of a multicenter observational study (Abdominal Sepsis Study, AbSeS) including 2621 adult ICU patients with intra-abdominal infection in 306 ICUs from 42 countries. Time-till-source control intervention was calculated as from time of diagnosis and classified into 'emergency' (< 2 h), 'urgent' (2-6 h), and 'delayed' (> 6 h). Relationships were assessed by logistic regression analysis and reported as odds ratios (OR) and 95% confidence interval (CI). Results: The cohort included 1077 cases of microbiologically confirmed secondary peritonitis. Mortality was 29.7%. The rate of appropriate empiric therapy showed no difference between survivors and non-survivors (66.4% vs. 61.3%, p = 0.1). A stepwise increase in mortality was observed with increasing Sequential Organ Failure Assessment (SOFA) scores (19.6% for a value ≤ 4-55.4% for a value > 12, p < 0.001). The highest odds of death were associated with septic shock (OR 3.08 [1.42-7.00]), late-onset hospital-acquired peritonitis (OR 1.71 [1.16-2.52]) and failed source control evidenced by persistent inflammation at day 7 (OR 5.71 [3.99-8.18]). Compared with 'emergency' source control intervention (< 2 h of diagnosis), 'urgent' source control was the only modifiable covariate associated with lower odds of mortality (OR 0.50 [0.34-0.73]). Conclusion: 'Urgent' and successful source control was associated with improved odds of survival. Appropriateness of empirical antimicrobial treatment did not significantly affect survival suggesting that source control is more determinative for outcome