Transport protocol and services

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FLOWER - Fuzzy lower than-best effort transport protocol

FLOWER - Fuzzy lower than-best effort transport protocol

I. I NTRODUCTION While standard TCP and its variants endeavor to achieve a fair share of the network bottleneck capacity between flows, the service provided by the network remains best-effort. There exists another service named Lower-than-Best-Effort (LBE) which aims at providing a second priority class inside the network traffic. The rationale is to propose a service for background traffic (e.g. peer-to-peer file transfers, data backup, software updates, . . . ) or signaling traffic. This kind of traffic might tolerate a high latency and should not disturb the traffic carried out by the best-effort service itself or other services that would propose advanced QoS architecture for time-constrained application such as DiffServ [1]. Today, the LBE service, also called “scavenger” service, is perceived as a potential solution to fetch the unused, sometimes wasted capacity in public network. One of the objective is, for instance, to provide a free Internet access based on this LBE principle, as illustrated
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Performance evaluation of multipath transport protocol in heterogeneous network environments

Performance evaluation of multipath transport protocol in heterogeneous network environments

[12], [13] and Concurrent Multipath Transfer extension of SCTP (CMT-SCTP) [14], are the transport protocol extensions which have received most attention in the research literature in recent years. Most research works [14], [?] only address an environment in which there is little difference between the multiple paths defined by the two components of the multipath (end to end) transport protocol. This is clearly not the case with e.g. 3G (or other cellular networks) and Wi-Fi, with the former having a lower offered bandwidth in current cellular services and significantly higher delay [REF]. Although in some cases, like free public hot spots, the Wi-Fi bandwidth offering may also be lower than e.g. 3G, the main premise of the asymmetry between the network paths being in place will still hold.
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Design, implementation and evaluation of a QoS-aware transport protocol

Design, implementation and evaluation of a QoS-aware transport protocol

In the context of a reconfigurable transport protocol framework, we propose a QoS-aware Transport Protocol (QSTP), specifically designed to operate over QoS-enabled networks with bandwidth guarantee. QSTP combines QoS-aware TFRC congestion control mech- anism, which takes into account the network-level bandwidth reservations, with a Selective ACKnowledgment (SACK) mechanism in order to provide a QoS-aware transport service that fill the gap between QoS enabled network services and QoS constraint applications. We have developed a prototype of this protocol in the user-space and conducted a large range of measurements to evaluate this proposal under various network conditions. Our results show that QSTP allows applications to reach their negotiated QoS over bandwidth guar- anteed networks, such as DiffServ/AF network, where TCP fails. This protocol appears to be the first reliable protocol especially designed for QoS network architectures with bandwidth guarantee.
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Promoting the use of reliable rate-based transport protocols: the Chameleon protocol

Promoting the use of reliable rate-based transport protocols: the Chameleon protocol

Recent work on transport protocols, such as TFRC and DCCP (Handley et al., 2008; Kohler et al., 2006), have proposed alternatives to the generally used window- based congestion control in particular for multimedia applications. This idea is not new as the RAP protocol can be considered as the precursor in this area (Rejaie et al., 1999). However, the motivation behind was different. RAP’s goal was to slow down the development of application level congestion controls implemented on top of a UDP socket. Indeed, application-layer transport protocols might induce an increase of this new kind of “congestion-controlled” UDP traffic that would not strictly follow the fair-share principle introduced in (Jacobson, 1988) and might lead to a bad equilibrium of the Internet nay, a new congestion collapse. Thus, DCCP and TFRC compute a sending rate which reproduces the long-term TCP behaviour and have been defined as an alternative to UDP to carry multimedia traffic while respecting the fair-share principle introduced in (Jacobson, 1988). Compared to other contributions (such as TCP variants), DCCP is the first protocol that enables two classes of congestion control mechanisms (window and rate-based) which have been conceived to specifically target applications needs before network performances. Indeed, actual congestion control mechanisms only focus on the network congestion and do not take into account neither the application’s needs nor the new network services while DCCP includes multiple congestion control algorithms which can be selected in regards to the user needs.
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Promoting the use of reliable rate based transport protocols: the Chameleon protocol

Promoting the use of reliable rate based transport protocols: the Chameleon protocol

Recent work on transport protocols, such as TFRC and DCCP (Handley et al., 2008; Kohler et al., 2006), have proposed alternatives to the generally used window- based congestion control in particular for multimedia applications. This idea is not new as the RAP protocol can be considered as the precursor in this area (Rejaie et al., 1999). However, the motivation behind was different. RAP’s goal was to slow down the development of application level congestion controls implemented on top of a UDP socket. Indeed, application-layer transport protocols might induce an increase of this new kind of “congestion-controlled” UDP traffic that would not strictly follow the fair-share principle introduced in (Jacobson, 1988) and might lead to a bad equilibrium of the Internet nay, a new congestion collapse. Thus, DCCP and TFRC compute a sending rate which reproduces the long-term TCP behaviour and have been defined as an alternative to UDP to carry multimedia traffic while respecting the fair-share principle introduced in (Jacobson, 1988). Compared to other contributions (such as TCP variants), DCCP is the first protocol that enables two classes of congestion control mechanisms (window and rate-based) which have been conceived to specifically target applications needs before network performances. Indeed, actual congestion control mechanisms only focus on the network congestion and do not take into account neither the application’s needs nor the new network services while DCCP includes multiple congestion control algorithms which can be selected in regards to the user needs.
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Which Transport Protocol for Hybrid Terrestrial and Satellite Systems?

Which Transport Protocol for Hybrid Terrestrial and Satellite Systems?

This paper proposes the evaluation of different TCP versions, using real stacks, in the specific problematic of the handover between terrestrial and satellite networks. The good behavior of the transport layer is crucial to offer quality services over hybrid networks. The surprising conclusion of this study is that windows seven compound gives very good results, in some cases better than those with PEP's, especially over large propagation delays. Tests with the "break before make" showed the difficulties of some TCP restart compared to others, and attest CTCP as the best version for handovers with or without breaks.
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Which Secure Transport Protocol for a Reliable HTTP/2-based Web Service : TLS or QUIC ?

Which Secure Transport Protocol for a Reliable HTTP/2-based Web Service : TLS or QUIC ?

Even if QUIC/UDP is currently used only by Google servers and Chrome/Chromium browsers, it represents an increasing part of the network traffic (many people use Google services). It is thus of prime importance to evaluate the protocol and identify if other web providers could have an interest to move to HTTP/2 over QUIC [4]. The interest can be driven by two aspects : performance and security. Some research studies such as [5] [6] compare the two protocols for a HTTP/2 web server in terms of performance (page load time, object size, server distribution, etc.). But to the best of our knowledge, there is no paper aiming to compare HTTP/2 on top of TLS/TCP and QUIC/UDP focused at security. This is the goal of this paper. We aim at identifying the possible vulnerabilities of both TLS/TCP and QUIC/UDP, evaluating their impacts on HTTP/2-based services. Our main goal is to give hints to web server developers or administrators on whether they should provide their HTTP/2 web service with TLS/TCP or QUIC/UDP.
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FLOWER, an Innovative Fuzzy Lower-than-Best-Effort Transport Protocol

FLOWER, an Innovative Fuzzy Lower-than-Best-Effort Transport Protocol

Abstract We present a new delay-based transport protocol named FLOWER, that aims at providing a Lower-than-Best-Effort (LBE) service. The objective is to propose an alternative to the Low Extra Delay Background Transport (LEDBAT) widely deployed within the official BitTorrent client. Indeed, besides its intra-fairness problem, known as latecomer unfairness, LEDBAT can be too aggressive against TCP, making it ill suited for providing LBE services over certain networks such as constrained wireless networks. By using a fuzzy controller to modulate the sending rate, FLOWER aims to solve LEDBAT issues while fulfilling the role of a LBE protocol. FLOWER operates to a modification of the standard LEDBAT protocol implementation by replacing its proportional controller by a fuzzy controller. Thanks to this modification, our simulation results show that FLOWER can carry LBE traffic in network scenarios where LEDBAT cannot while solving the latecomer unfairness problem. The presented algorithm is simple to implement and does not require complex computation that would prevent its deployment. Finally, we show that FLOWER remains compliant when used over an AQM-based network and remains LBE while not increasing the bufferbloat.
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QoS Enhancements and the new transport services

QoS Enhancements and the new transport services

performance is not fulfilled. NEED OF A NEW TRANSPORT SERVICE In the previous sections, we tried to stress that the improvement of the transport service and protocol does not lie only on the performance, but that it will be necessary to extend the characteristics of the offered services. This opinion was already expressed in [ChW,89] to advocate a new generation of communication systems : “By ‘new generation’ we mean that the design of protocols, networks and network interfaces should be rethought from the first principles in the context of the new environment. Refining existing designs and tuning conventional approaches in the area are inadequate, given the magnitude of changes that have taken place. At the same time, we need to be extremely careful to identify the key problems of the current standard protocols and come up with a convincing solution that is significantly better than these protocols. That is, we clearly recognise that an incremental improvement over existing protocols, such as the stream-oriented TCP or ISO TP4, would not warrant a new protocol or modifications to the existing protocols, given the enormous investment already in place.”
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Towards a Versatile Transport Protocol

Towards a Versatile Transport Protocol

worldcup, where cellular phones service providers have mea- sured a significant increase of the multimedia traffic. Con- versely to powerful multimedia streaming servers, mobile end systems are resource-limited. Therefore the lighten- ing of recurrent communication processing is a critical issue for increasing performances and autonomy of mobiles end systems. Additionally, new QoS oriented network services, adapted to media streaming, have emerged. However cur- rent transport protocol are not able to map application layer needs down to these services. This paper addresses the chal- lenge of designing a versatile transport protocol capable of performing efficiently over multiple network contexts.
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Towards a versatile transport protocol

Towards a versatile transport protocol

CoNEXT’06, 4-7 December 2006, Lisboa, Portugal. Copyright 2006 ACM 1-59593-456-1/06/12 ... $ 5.00. worldcup, where cellular phones service providers have mea- sured a significant increase of the multimedia traffic. Con- versely to powerful multimedia streaming servers, mobile end systems are resource-limited. Therefore the lighten- ing of recurrent communication processing is a critical issue for increasing performances and autonomy of mobiles end systems. Additionally, new QoS oriented network services, adapted to media streaming, have emerged. However cur- rent transport protocol are not able to map application layer needs down to these services. This paper addresses the chal- lenge of designing a versatile transport protocol capable of performing efficiently over multiple network contexts.
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FLOWER, an innovative Fuzzy Lower-than-Best-Effort transport protocol

FLOWER, an innovative Fuzzy Lower-than-Best-Effort transport protocol

Abstract We present a new delay-based transport protocol named FLOWER, that aims at providing a Lower-than-Best-Effort (LBE) service. The objective is to propose an alternative to the Low Extra Delay Background Transport (LEDBAT) widely deployed within the official BitTorrent client. Indeed, besides its intra-fairness problem, known as latecomer unfairness, LEDBAT can be too aggressive against TCP, making it ill suited for providing LBE services over certain networks such as constrained wireless networks. By using a fuzzy controller to modulate the sending rate, FLOWER aims to solve LEDBAT issues while fulfilling the role of a LBE protocol. FLOWER operates to a modification of the standard LEDBAT protocol implementation by replacing its proportional controller by a fuzzy controller. Thanks to this modification, our simulation results show that FLOWER can carry LBE traffic in network scenarios where LEDBAT cannot while solving the latecomer unfairness problem. The presented algorithm is simple to implement and does not require complex computation that would prevent its deployment. Finally, we show that FLOWER remains compliant when used over an AQM-based network and remains LBE while not increasing the bufferbloat.
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Pépite | Validité du Blue Protocol dans l’orientation étiologique des difficultés respiratoires au sein des services d’urgences du Nord-Pas-de-Calais

Pépite | Validité du Blue Protocol dans l’orientation étiologique des difficultés respiratoires au sein des services d’urgences du Nord-Pas-de-Calais

La plus grosse différence est observée sur la spécificité et la valeur prédictive positive pour l’exacerbation d’asthme ou de BPCO ce qui s’explique par notre choix dans l’étude de nous baser sur le diagnostic final pour classer les différentes pathologies. Lorsque le patient n’avait aucune pathologie pulmonaire c’est à dire que le poumon était « sain » il était classé dans « autre » de même que pour les bronchites. Le profil d’asthme ou de BPCO est un profil dit « nu » ce qui correspond à un aspect échographique normal. Dans l’arbre décisionnel du Blue Protocol, il n’existe pas de profil normal, tout profil amène à une pathologie pour des patients étudiés avec une hémodynamique instable. Or le poumon d’un patient BPCO ou asthmatique n’est pas un poumon « sain » même si son profil échographique correspond à un profil « nu ». Pour les urgences il faudrait donc parler d’étiologie sans anomalie échographique décelée au lieu d’asthme ou de BPCO pour le profil « nu », pour intégrer les exacerbations d’asthme ou de BPCO ainsi que les bronchites et les patients sans pathologie pulmonaire.
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Virtual Trials of the NICE-SUGAR Protocol: The Impact on Performance of Protocol and Protocol Compliance

Virtual Trials of the NICE-SUGAR Protocol: The Impact on Performance of Protocol and Protocol Compliance

The NICE-SUGAR intensive insulin therapy protocol (NS- IIT) targeted a glycaemic range of 4.5-6.0 mmol/l (81-108 mg/dL), where the conventional control was < 10.0 mmol/L (< 180mg/dL). For both aims, insulin was delivered as a continuous intravenous infusion of insulin alongside glucose boluses, and the nutritional management was carried out at the discretion of the treating clinicians (Finfer et al., 2009). Further explanation of this risk-based approach protocol can be found in (Finfer et al., 2009). NS-IIT was implemented directly from the reported protocol, and nutrition increased in simulation daily to reflect reported non-protein calorie achievements (Finfer et al., 2009). As nutrition type/composition was never reported, and ICU nutrition types can vary in their glucose composition, it was assumed that enteral nutrition was low carb (~40% of non-protein calories were CHO, similar to Glucerna 1.0 TM ), and that parenteral nutrition had 70% of non-protein calories attributable to CHO. Simulating with a low-carb enteral nutrition is conservative, and reflects a best case outcome for the NICE-SUGAR protocol, as increased dextrose intake tends to make glycaemic control more difficult and magnifies patient variability. STAR differs from NICE-SUGAR as it is a computerised model-based glycaemic control protocol, and uses a stochastic model to assess likely future change of patient-specific time- varying insulin sensitivity (SI) (Evans et al., 2012, Lin et al., 2008, Fisk et al., 2012). Current SI is determined from the clinically validated ICING physiological model (Lin et al., 2011), using integral-based fitting methods (Hann et al., 2005). A stochastic model was built based on population data, allowing forecasting of future changes in SI, and thus BG for a given insulin/nutrition combinations, and thus corresponding BG outcomes. STAR selects an optimal insulin and nutrition dose to best overlap predicted BG outcomes with the BG target range (4.4-8.0 mmol/L or 80-144 mg/dL), maximizing both safety and performance. Hypoglycaemic risk is directly managed, with the predicted likelihood of BG < 4.4 mmol/L (< 80 mg/dL) limited to a maximum value of 5%, by directly placing the BG outcome for the 95 th percentile future SI value on 4.4 mmol/L.
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Réglementation, gouvernance et performance des services publics de transport collectif urbain

Réglementation, gouvernance et performance des services publics de transport collectif urbain

• Modifications de l’offre de transport • Changements de la politique tarifaire L’approche institutionnaliste ou néo-instituionnaliste, dont Coase (1937) est à l’origine, se concentre notamment sur les modes de coordination des acteurs (Ménard 2003). Williamson (1976) et Goldberg (1976) proposent d’appliquer la méthode d’analyse de la théorie des coûts de transaction dans la fourniture des services publics. Ils utilisent notamment cette grille d’analyse pour mettre en évidence certaines limites de la mise aux enchères telle qu’elle est proposée par Demsetz (1968). Ce type d’analyse peut s’appliquer au problème qui nous intéresse, de nombreuses études existent concernant la réglementation des industries de réseaux (Glachant 2002). La théorie des coûts de transaction procure un cadre tout à fait pertinent pour aborder la question de l’adaptation pour chaque mode de gouvernance (Yvrande 2002). Typiquement, la question que l’on se pose est celle de la capacité des différents modes de gouvernance des transports urbains à permettre une modification de l’offre (ou de la tarification) en cours de contrat, au moindre coût.
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Politiques de tarification des services de transport urbain. Diagnostic de pratiques comparatives

Politiques de tarification des services de transport urbain. Diagnostic de pratiques comparatives

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

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Les effets du régime des services essentiels sur la négociation collective : études de cas dans les secteurs du transport en commun et de la santé et des services sociaux

Les effets du régime des services essentiels sur la négociation collective : études de cas dans les secteurs du transport en commun et de la santé et des services sociaux

rôle lorsque le régime des services essentiels contraint un grand nombre de salariés à poursuivre le travail en temps de grève. Comme le régime des services essentiels interdit la grève générale illimitée pour l’ensemble des travailleurs, la partie syndicale doit faire preuve de créativité afin d’exercer des moyens de pression autres. Ces moyens de pression sont de nature différente et la fréquence de ceux-ci diffère de la grève générale. Ils diffèrent de celle-ci, car l’ensemble des membres du syndicat ne peuvent plus cesser de travailler en attente d’un règlement possible. Ils doivent en partie poursuivre le travail tout en souhaitant l’obtention d’un règlement. L’étude de Grant et Racine (1992) montre que les syndicats, soumis à l’obligation de maintenir les services essentiels, ont mis de côté la grève générale illimitée pour la remplacer par des grèves rotatives de plus courte durée ou encore par des moyens de pression autres que la grève. Par conséquent, la nature et la fréquence des moyens de pression devraient être diversifiées dans les secteurs assujettis au régime des services essentiels comme ceux à l’étude dans le cadre de cette recherche. Enfin, il se peut que les variantes du régime n’aient pas d’effet sur la nature et la fréquence des moyens de pression, mais peut-être que le pourcentage fixe, l’avis de 20 jours, le maintien du fonctionnement normal en cas d’urgence et des soins intensifs et le libre accès des bénéficiaires forcent le syndicat à développer des moyens de pression alternatifs. Les restrictions additionnelles dans ce secteur sont peut-être plus contraignantes que ne l’est la limitation du droit de grève. Cependant, il est difficile de se prononcer sur les effets de ces variantes sur la nature et la fréquence des moyens de pression.
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The renegotiation cost of public transport services contracts

The renegotiation cost of public transport services contracts

Since 1993, “beauty contests” are required to allocate the building and manage- ment of new infrastructures for urban transportation when the date for contract re- newal comes. However, and until recently, very few networks have changed operators from one regulatory period to the other. Documentary investigations shed light on the fact that awarding transport operations through tenders does not necessarily foster ex ante competition since most local authorities usually receive bids from only one firm, namely the operator already in charge. Several reasons might explain this phenom- enon. First, local authorities are either reluctant to implement the law or do not have enough expertise to launch complex calls for tender. Second, the three groups owning most of the urban operators in France are located on specific geographical areas which restricts competition. Finally, these groups also operate other municipal services such as water distribution or garbage collection, which makes it even harder for public au- thorities to credibly punish operators following bad performances.
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le rapport entre la qualité des services et la  satisfaction des clients Cas : transport routier.

le rapport entre la qualité des services et la satisfaction des clients Cas : transport routier.

30 Chapitre 2 : la satisfaction client et sa mesure Introduction au chapitre L’objectif suprême de l’entreprise est de créer une clientèle. Mais, pour conquérir durablement un client, il faut d’abord bien connaître ses besoins et ses modes d’achat, car le client aujourd’hui, cherche parmi les produits ou les services offerts, ceux qui procurent le maximum de satisfaction. Cette dernière conduit à une fidélisation. Ces deux notions sont l’objet de notre recherche dans ce chapitre, où nous allons essayer de les cerner (satisfaction, et fidélisation) à travers l’étude de différents éléments qui les composent à savoir : leurs définitions, leurs caractéristiques puis nous déterminerons comment satisfaire le client et comment réaliser cette satisfaction à travers des méthodes et techniques auxquelles doit faire appel l’entreprise. Enfin, nous allons expliquer l’interaction entre la satisfaction et la qualité de service.
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Toward a versatile transport protocol

Toward a versatile transport protocol

4.2.1 TCP over DiffServ/AF class Many studies related to the performance of TCP-flow over assured service have already been conducted. In [ SNP99 ], five factors have been studied (RTT, number of flows, target rate, packet size, non responsive flows) and their impact has been evaluated in order to provide a predictable service to TCP flows. In an over-provisioned network, the target rate associated with the in-profile traffic is achieved regardless of these five factors. However, these factors have a deep impact on the distribution of the out-profile excess bandwidth. In their paper [ PC04a ], Park and Choi demonstrate the unfair allocation of out-profile TCP traffic and conclude that the smaller target rate aggregate (resp. larger target rate) occupies more (resp. less) bandwidth than its fair-share regardless of the subscription level. As the TCP protocol uses the AIMD congestion control algorithm which fairly shares the bandwidth available, the only mean to obtain a service differentiation with the TCP protocol is to use DiffServ traffic conditioners such as token bucket color marker (TCM) [ HG99 ] or time sliding window color marker (TSWCM) [ FSa00 ]. The behaviour of these traffic conditioners has a great impact on the service level, in terms of bandwidth obtained by TCP flows. Several others conditioners have been proposed to improve throughput insurance [ EGS02 ], [ FRK00 ], [ HBF02 ], [ KAJ01 ], [ LAF05a ], [ LAF05b ], [ NPE00 ]. These contributions clearly showed that the key parameters to the TCP throughput guarantee problem are given by loss_probability, the RT T and the target_rate) associated to each flow.
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