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International audience; The Low-Latency Low-Loss Scalable throughput (L4S) architecture has recently been proposed to reduce the network latency of low-latency services and to allow their flows to coexist with classic ones in the same domain. This coexistence implies monitoring and security challenges. However current monitoring methods, primarily based-on sampling and polling, exhibit performance and granularity limitations. This paper describes the challenges for monitoring LL services and details our solution when introducing a fine-grained and real-time monitoring capability in our P4-based L4S implementation using In-band Network Telemetry. The initial experimental evaluation shows that our solution is able to monitor the metrics of an L4S switch with very few networking and processing overhead and without disturbing the L4S behaviour.

International audience; Cloud Gaming (CG) has been gaining a lot of interest and major actors have entered this market such as Google, Nvidia, Sony or Microsoft. They operate CG platforms that attract an increasing number of players worldwide. This type of traffic is highly demanding for network infrastructures because it requests simultaneously high bandwidth, low delay and no traffic degradation (interruptions or jitter) to ensure a good end-user's QoE. To improve the delivery of low-latency applications, new Active Queue Management architectures like L4S (Low Latency, Low Loss, Scalable Throughput) are proposed. Currently, traffic is routed to a low-latency queue only based on the presence of the Explicit Congestion Notification bit (ECN) in the IP header, but this is too restrictive and can be easily manipulated. Instead, we aim at analyzing and detecting CG traffic based on its inherent characteristics, to forward the packets in the low-latency queue. This paper presents our models to efficiently detect CG traffic based on flow-level features among other highbitrate applications transported over UDP. The evaluation proves that our model based on decision trees achieves very good results (98.5% accuracy) and can be realistically deployed as a Virtualized Network Function at the edge, handling more than 10Gb/s of medium-sized flows on a low-end server. Our network captures and source code are open to ensure reproducible results.

In recent years, optical frequency combs with a frequency modulated output have attracted considerable attention. While first observed decades ago in externally modulated lasers, a whole class of semiconductor lasers has since been identified to spontaneously enter such a regime of self frequency modulation. The temporal properties of these sources are commonly measured indirectly via phase-resolved frequency domain measurements. In this work, they demonstrate an asynchronous optical sampling technique which operates directly in time domain.. On the basis of a mid-infrared quantum cascade laser frequency comb, both its instantaneous intensity and optical frequency are measured. The results confirm a quasi-constant intensity output alongside a close to linear frequency chirp, in accordance with phase-resolved spectral measurements. Contrary to previous works, stable phase-locking is achieved in a regime of positive intracavity dispersion resulting in an inversion of the observed frequency modulation., Laser & Photonics Reviews, 4, ISSN:1863-8880, ISSN:1863-8899, 17

International audience; New services with low-latency (LL) requirements are one of the major challenges for the envisioned Internet. Many optimizations targeting the latency reduction have been proposed, and among them, jointly rearchitecting congestion control and active queue management (AQM) has been particularly considered. In this effort, the L4S (Low Latency, Low Loss and Scalable Throughput) proposal aims at allowing both Classic and LL traffic to cohabit within a single node architecture. Although this architecture sounds promising for latency improvement, it can be exploited by an attacker to perform malicious actions whose purposes are to defeat its LL feature and consequently make their supported applications unusable. In this paper, we exploit different vulnerabilities of L4S which are the root of possible attacks and we show that application-layer protocols such as QUIC can easily be hacked in order to exploit the over-sensitivity of those new services to network variations. By implementing such undesirable flows in a real testbed and characterizing how they impact the proper delivery of LL flows, we demonstrate their reality and give insights for research directions on their detection.; De nouveaux services avec des exigences de faible latence constituent un des défis majeurs de l'Internet envisagé pour le futur. Beaucoup d'optimisations ciblant la latence ont été proposés, et parmi elles, la ré-architecture conjointe du contrôle de congestion avec la gestion active des files d'attentes a été particulièrement considéré. Dans cette optique, la proposition L4S (Low Latency, Low Loss and Scalable Throughput) vise à permettre la coexistence entre du trafic classique et du trafic faible latence au sein du même noeud réseau. Bien que cette architecture semble prometteuse pour l'amélioration de la latence, elle peut être exploitée par un attaquant réalisant des actions malicieuses ayant pour but de déjouer la garantie de faible latence, rendant de fait les services associés instables.Dans cet article, nous exploitons différentes vulnérabilités de L4S qui sont au coeur des attaques possibles et nous montrons que des protocoles de niveau applicatif tel que QUIC peuvent être facilement détournés dans le but d'exploiter l'hypersensibilité de ces nouveaux services aux variations réseaux. En implémentant de tels flux indésirables dans un banc de tests réaliste, et en caractérisant de quelle manière ils impactent la cadence de livraison des paquets des flux faibles latence, nous démontrons leur réalité et donnons des pistes de recherche pour leur détection.

ERI Network & Telecom - EUt+ Workshop; New services are designed for the future of Internet, and some of them will require the network to provide low latency traffic. Many optimizations targeting latency reduction have been proposed. Among them, re-architecting congestion control and active queue management (AQM) has been particularly studied. L4S [1,2,3] (Low Latency, Low Loss and Scalable Throughput) is a new network architecture that aims at allowing coexistence between low latency traffic and classic traffic within a single node, involving a dual queue coupled AQM. Although this architecture sounds promising for latency improvement, an attacker can exploit some vulnerabilities to defeat its low-latency features and consequently make some services unusable. In addition, we prove that application-layer protocols such as QUIC can easily be hacked in order to exploit the over sensitivity of those new services to network variations. By implementing undesirable flows in a testbed and evaluating how they impact the delivery of low-latency flows, we demonstrate their reality and the need of research in the detection of this new kind of threats [4,5].; De nouveaux services sont conçus pour l'avenir de l'Internet, et certains d'entre eux exigeront que le réseau fournisse un trafic à faible latence. De nombreuses optimisations visant à réduire la latence ont été proposées. Parmi elles, la réarchitecture du contrôle de la congestion et de la gestion active des files d'attente (AQM) a été particulièrement étudiée. L4S [1,2,3] (Low Latency, Low Loss and Scalable Throughput) est une nouvelle architecture de réseau qui vise à permettre la coexistence du trafic à faible latence et du trafic classique au sein d'un même nœud, en faisant intervenir un AQM couplé à une double file d'attente. Bien que cette architecture semble prometteuse en termes d'amélioration de la latence, un attaquant peut exploiter certaines vulnérabilités pour contourner ses caractéristiques de faible latence et, par conséquent, rendre certains services inutilisables. En outre, nous prouvons que les protocoles de la couche application tels que QUIC peuvent facilement être piratés afin d'exploiter la sensibilité excessive de ces nouveaux services aux variations du réseau. En implémentant des flux indésirables dans un banc d'essai et en évaluant leur impact sur la livraison des flux à faible latence, nous démontrons leur réalité et le besoin de recherche dans la détection de ce nouveau type de menaces [4,5].

Quantum cascade lasers are versatile light sources in the mid-infrared range for molecular spectroscopy which find a wide range of applications from high-resolution studies to sensing. While devices with either high power or narrow spectral linewidth have previously been reported, there is still a lack of sources combining both of these characteristics which are particularly important for precision measurements of weak spectroscopic transitions. In this article, we describe and characterize a novel master-oscillator power-amplifier distributed-feedback quantum cascade laser designed to fill this gap. At an output power of 300 mW, the device features a free-running linewidth of 1.3 MHz, measured with a frequency discriminator technique, at an emission wavenumber of 2185 cm−1. This linewidth is sufficiently narrow to enable a further reduction by a tight lock to a high-Q oscillator.

International audience; Low-latency applications (cloud-gaming, cloud-robotics, metaverse...) have soared with the rapid evolution of Internet. Current network capacities (especially time-varying capacity networks like 4G/5G networks) struggle to ensure user QoE (Quality of Experience). There is therefore a need to collect, identify and analyze metrics specific to low-latency applications in network equipment (switches, base stations, UEs...) for efficient troubleshooting of user QoE degradation purposes.

Fast (sub-second) spectroscopy with high spectral resolution is of vital importance for revealing quantum chemistry kinetics of complex chemical and biological reactions. Fourier transform (FT) spectrometers can achieve high spectral resolution and operate at hundreds of ms time scales in rapid-scan mode. However, the linear translation of a scanning mirror imposes stringent time-resolution limitations to these systems, which makes simultaneous high spectral and temporal resolution very difficult. Here, we demonstrate an FT spectrometer whose operational principle is based on continuous rotational motion of the scanning mirror, effectively decoupling the spectral resolution from the temporal one. Furthermore, we show that such rotational FT spectrometer can perform Mid-IR dual-comb spectroscopy with a single comb source, since the Doppler-shifted version of the comb serves as the second comb. In our realization, we combine the advantages of dual-comb and FT spectroscopy using a single quantum cascade laser frequency comb emitting at 8.2 μm as a light source. Our technique does not require any diffractive or dispersive optical elements and hence preserve the Jacquinot’s-, Fellgett’s-, and Connes’-advantages of FT spectrometers. By integrating mulitple broadband sources, such system could pave the way for applications where high speed, large optical bandwidth, and high spectral resolution are desired., Communications Physics, 6 (1), ISSN:2399-3650

High precision measurement of multiply substituted ("clumped") isotopologues of CO2 is a topic of significant interest in the fields of isotope geochemistry and paleoclimate research [1, 2]. The temperature-dependent behavior of 13C and 18O isotopes in gaseous carbon dioxide is widely used as a temperature proxy for paleoclimate reconstruction. The basis for it lies in the temperature dependence of the equilibrium constant, K(T), of the isotope exchange reactions 12C18O2 + 12C16O2 ↔ 2٠12C16O18O and 13C16O18O + 12C16O2 ↔ 13C16O2+12C16O18O [3, 4] as these reactions have a slight tendency to move towards the right at higher temperatures. Currently, the established method to perform clumped isotope thermometry is Isotope Ratio Mass Spectrometry (IRMS) [5]. However, IRMS measurements, in particular for rare isotopologues, typically require several hours of analysis time and extensive sample preparation to properly separate isobaric interferences. In contrast to IRMS, optical absorption spectroscopic techniques allow the realisation of isotopologue specific, non-destructive, and compact spectrometers with short analysis time and high-precision capabilities. Recently, Wang et al. [6], Prokhorov et al. [3], and Nataraj et al. [4] have demonstrated the great promise of laser absorption spectroscopy for measurements of clumped isotopes of carbon dioxide.The major challenge for clumped isotope thermometry using 12C18O2 resides in its very low natural relative abundance (4.1 ppm) and the spectral interference from the major (12C16O2) and singly substituted isotopologues. These factors seriously limit the achievable analytical performance of spectroscopic measurements and thus the applicability of this technique. However, the interference caused by the hot-band transitions of the abundant species can be suppressed by reducing the gas temperature. Moreover, working at low pressure (5 mbar) narrows the absorption lines and reduces the overlap between neighbouring transitions.Here, we present a novel quantum cascade laser absorption spectrometer (QCLAS) employing a low-volume segmented circular multipass cell (SC-MPC) [7] operated at cryogenic temperatures (153 K) and low pressure (5 mbar). For the first time, we optically measure the abundances of all three isotopologues involved in the reaction 12C18O2 + 12C16O2 ↔ 2٠12C16O18O simultaneously. We report a precision of 0.05 ‰ in the isotope ratios [12C18O2/12C16O2] and [12C16O18O/12C16O2] with 25 s integration time. In addition, we determine and resolve the tiny variation in the equilibrium constant, K(T), of the above exchange reaction for carbon-dioxide samples equilibrated at 300 K and 1273 K, respectively. This versatile system can be extended to other chemical species where spectroscopic measurements are impacted by the hot-band transitions of abundant isotopologues — (e.g., methane and its deuterated isotopologues, CH3D and CH2D2, or propane and the two isotopomers, 12CH313CH212CH3 and 13CH312CH212CH3) — thereby opening up new perspectives in environmental sciences and fundamental research.[1] J. M. Eiler, Quaternary Science Reviews,doi: 10.1016/j.quascirev.2011.09.001.[2] S. M. Bernasconi et al., Applied Geochemistry doi: 10.1016/j.apgeochem.2011.03.080.[3] I. Prokhorov et a.l, Sci Rep, doi: 10.1038/s41598-019-40750-z.[4] A. Nataraj et al., Optics Express accepted, doi:10.1364/OE.447172[5] Fiebig et al, Chemical Geology doi: 10.1016/j.chemgeo.2019.05.019[6] Z. Wang et al., Anal. Chem., doi: 10.1021/acs.analchem.9b04466.[7] M. Graf et al.,Optics Letters doi: 10.1364/OL.43.002434.

Riche et lumineuse, la carrière du professeur Jean-Claude Masclet s’est spontanément mise au service de l’Université. Jamais rétif à l’exercice de la fonction universitaire ou de la charge administrative, il s’est utilement dévoué à la diffusion du savoir et de l’enseignement du droit. Le professeur Jean-Claude Masclet a oeuvré, avec belle intuition, à l’éclosion et l’essor de plusieurs champs du droit constitutionnel, alors naissants, méconnus ou peu explorés. À l’idée européenne, celui-ci a consacré nombre de ses écrits dont certains ont été traduits en plusieurs langues. Inlassablement, Jean-Claude Masclet a été animé par la volonté d’expliquer la vertu de l’Europe politique comme celle de l’Europe du droit. Avec conviction et habilité, il a su porter par les nombreux travaux que décline sa bibliographie la beauté de l’idéal européen. Les études ici réunies ne pouvaient alors que s’attarder sur ses thèmes de prédilection : la Constitution et l’Europe. L’ouvrage, résolument inscrit dans l’inégalable tradition universitaire des Mélanges, convie l’esprit avide de compréhension à arpenter les champs infinis que déploient les droits constitutionnel et européen.

La recherche de freins renvoie à une conception libérale du pouvoir. Elle sous-entend la dangerosité du pouvoir dans la logique exprimée par Montesquieu selon laquelle qui a du pouvoir a tendance à en abuser et seul le pouvoir arrête le pouvoir. Cette analyse fondamentale a conduit les constitutions occidentales depuis la fin du xviiie siècle, puis la plupart des Constitutions des États se concevant comme des États de droit à rechercher des systèmes d’équilibre entre les pouvoirs. C’est cette...

We present a quantum cascade laser-based absorption spectrometer deploying a compact (145 mL volume) segmented circular multipass cell (SC-MPC) with 6 m optical path length. This SC-MPC is embedded into an effective cooling system to facilitate operation at cryogenic temperatures. For CO