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Numrering	Referens	Omslagsbild	Hitta
1.	Ahlgren, Bengt, et al. (författare) Are MIRCC and Rate-based Congestion Control in ICN READY for Variable Link Capacity? 2017 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Information-centric networking (ICN) has been introduced as a potential future networking architecture. ICN promises an architecture that makes information independent from lo- cation, application, storage, and transportation. Still, it is not without challenges. Notably, there are several outstanding issues regarding congestion control: Since ICN is more or less oblivious to the location of information, it opens up for a single application flow to have several sources, something which blurs the notion of transport flows, and makes it very difficult to employ traditional end-to-end congestion control schemes in these networks. Instead, ICN networks often make use of hop-by-hop congestion control schemes. How- ever, these schemes are also tainted with problems, e.g., several of the proposed ICN congestion controls assume fixed link capacities that are known beforehand. Since this seldom is the case, this paper evaluates the consequences in terms of latency, throughput, and link usage, variable link capacities have on a hop-by-hop congestion control scheme, such as the one employed by the Multipath-aware ICN Rate-based Congestion Control (MIRCC). The evaluation was carried out in the OMNeT++ simulator, and demonstrates how seemingly small variations in link capacity significantly deterio- rate both latency and throughput, and often result in inefficient network link usage.
2.	Ahlgren, Bengt, et al. (författare) ICN congestion control for wireless links 2018 Ingår i: IEEE WCNC 2018 Conference Proceedings. - New York : IEEE. Konferensbidrag (refereegranskat)abstract Information-centric networking (ICN) with its design around named-based forwarding and in-network caching holds great promises to become a key architecture for the future Internet. Many proposed ICN hop-by-hop congestion control schemes assume a fixed and known link capacity, which rarely - if ever - holds true for wireless links. Firstly, we demonstrate that although these congestion control schemes are able to fairly well utilise the available wireless link capacity, they greatly fail to keep the delay low. In fact, they essentially offer the same delay as in the case with no hop-by-hop, only end-to-end, congestion control. Secondly, we show that by complementing these schemes with an easy-to-implement, packet-train capacity estimator, we reduce the delay to a level significantly lower than what is obtained with only end-to-end congestion control, while still being able to keep the link utilisation at a high level.
3.	Ahlgren, Bengt, et al. (författare) Latency-aware Multipath Scheduling inInformation-centric Networks 2019 Ingår i: Proceedings of the Fifteenth Swedish National Computer Networking Workshop (SNCNW), Luleå, Sweden. 4-5 June 2019.. Konferensbidrag (refereegranskat)abstract We present the latency-aware multipath schedulerZQTRTT that takes advantage of the multipath opportunities ininformation-centric networking. The goal of the scheduler is touse the (single) lowest latency path for transaction-oriented flows,and use multiple paths for bulk data flows. A new estimatorcalled zero queue time ratio is used for scheduling over multiplepaths. The objective is to distribute the flow over the paths sothat the zero queue time ratio is equal on the paths, that is,so that each path is ‘pushed’ equally hard by the flow withoutcreating unwanted queueing. We make an initial evaluation usingsimulation that shows that the scheduler meets our objectives.
4.	Alfredsson, Freysteinn, et al. (författare) XDQ : Enhancing XDP with Queuing and Packet Scheduling 2024 Ingår i: Proceedings of the 27th Conference on Innovation in Clouds, Internet and Networks, ICIN 2024. - : IEEE. - 9798350393774 - 9798350393767 ; , s. 52-56 Konferensbidrag (refereegranskat)abstract Modern internet users expect seamless, uninterrupted communication when using real-time applications, even when sharing the network connection with devices that produce heavy traffic. This trend has pushed the demand for more sophisticated packet schedulers on routers. However, given the limited resources on these routers, it is increasingly important to reduce the overhead associated with these schedulers. This paper presents XDP Queuing (XDQ), our ongoing work on achieving faster packet scheduling on the Linux operating system, which is popular on networking equipment. Linux provides eXpress Data Path (XDP), a high-performance programmable network data path using the eBPF framework, which allows code to process packets early from the driver. While XDP has found numerous uses in the industry, such as Denial-of-Service attack mitigation, load-balancers, and intrusion prevention systems, it currently has no mechanism for queueing or reordering packets and cannot implement traffic scheduling policies. Our contribution, XDQ, is a programmable packet scheduling extension for the XDP framework. XDQ uses recently proposed schemes for programmable queues. It allows writing packet schedulers using eBPF while benefiting from the XDP fast data path.
5.	Allman, Mark, et al. (författare) Early Retransmit for TCP and SCTP 2008 Annan publikation (populärvet., debatt m.m.)abstract This document proposes a new mechanism for TCP and SCTP that can be used to recover lost segments when a connection's congestion window is small. The "Early Retransmit" mechanism allows the transport to reduce, in certain special circumstances, the number of duplicate acknowledgments required to trigger a fast retransmission. This allows the transport to use fast retransmit to recover packet losses that would otherwise require a lengthy retransmission timeout.
6.	Amin, Khabat, et al. (författare) Analysis of road safety trends 2020 : Management by objectives for road safety work towards the 2020 interim targets 2021 Rapport (övrigt vetenskapligt/konstnärligt)abstract The Swedish road safety management is based on the Vision Zero and designated interim targets to track progress towards its achievement. 2020 was the final year for achieving the interim target of halving the number of fatalities between 2007 and 2020, i.e., a maximum of 220 fatalities in 2020. The interim target also specifies that the number of seriously injured in road traffic must be reduced by a quarter. This report describes and analyses the current road safety trends in terms of road safety performance indicators and the numbers of fatalities and seriously injured. As this report is the last for the 2007-2020 interim target period, it can be seen as a final summary of how well the targets were achieved for fatalities and seriously injured and for the safety performance indicators. However, it is also important to remember that the year 2020 coincided with the COVID-19 pandemic, which had a profound impact on virtually the entire society. This affected travel in a number of different ways, and consequently it is impossible to estimate the impact this has had on the outcome in 2020, although it probably has led to a slightly lower outcome. The table below shows starting and final values together with an overview of whether the safety performance indicators have met the 2020 targets.
7.	Ehn, Andreas, et al. (författare) Plasma assisted combustion: Effects of O3 on large scale turbulent combustion studied with laser diagnostics and Large Eddy Simulations 2015 Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 35:3, s. 3487-3495 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract Abstract In plasma-assisted combustion, electric energy is added to the flame where the electric energy will be transferred to kinetic energy of the free electrons that, in turn, will modify the combustion chemical kinetics. In order to increase the understanding of this complex process, the influence of one of the products of the altered chemical kinetics, ozone (O3), has been isolated and studied. This paper reports on studies using a low-swirl methane (CH4) air flame at lean conditions with different concentrations of O3 enrichment. The experimental flame diagnostics include Planar Laser Induced Fluorescence (PLIF) imaging of hydroxyl (OH) and formaldehyde (CH2O). The experiments are also modeled using Large Eddy Simulations (LES) with a reaction model based on a skeletal CH4-air reaction mechanism combined with an O3 sub-mechanism to include the presence of O3 in the flame. This reaction mechanism is based on fundamental considerations including reactions between O3 and all other species involved. The experiments reveal an increase in CH2O in the low-swirl flame as small amounts of O3 is supplied to the CH4-air stream upstream of the flame. This increase is well predicted by the LES computations and the relative radical concentration shift is in good agreement with experimental data. Simulations also reveal that the O3 enrichment increase the laminar flame speed, su, with ∼10% and the extinction strain-rate, Ïext, with ∼20%, for 0.57% (by volume) O3. The increase in Ïext enables the O3 seeded flame to burn under more turbulent conditions than would be possible without O3 enrichment. Sensitivity analysis indicates that the increase in Ïext due to O3 enrichment is primarily due to the accelerated chain-branching reactions H 2 + O â OH + H , H 2 O + O â OH + OH and H + O 2 â OH + O . Furthermore, the increase in CH2O observed in both experiments and simulations suggest a significant acceleration of the chain-propagation reaction CH 3 + O â CH 2 O + H .
8.	Ehn, Andreas, et al. (författare) Setup for microwave stimulation of a turbulent low-swirl flame 2016 Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 49:18 Tidskriftsartikel (refereegranskat)abstract An experimental setup for microwave stimulation of a turbulent flame is presented. A low-swirl flame is being exposed to continuous microwave irradiation inside an aluminum cavity. The cavity is designed with inlets for laser beams and a viewport for optical access. The aluminum cavity is operated as a resonator where the microwave mode pattern is matched to the position of the flame. Two metal meshes are working as endplates in the resonator, one at the bottom and the other at the top. The lower mesh is located right above the burner nozzle so that the low-swirl flame is able to freely propagate inside the cylinder cavity geometry whereas the upper metal mesh can be tuned to achieve good overlap between the microwave mode pattern and the flame volume. The flow is characterized for operating conditions without microwave irradiation using particle imaging velocimetry (PIV). Microwave absorption is simultaneously monitored with experimental investigations of the flame in terms of exhaust gas temperature, flame chemiluminescence (CL) analysis as well as simultaneous planar laser-induced fluorescence (PLIF) measurements of formaldehyde (CH2O) and hydroxyl radicals (OH). Results are presented for experiments conducted in two different regimes of microwave power. In the high-energy regime the microwave field is strong enough to cause a breakdown in the flame. The breakdown spark develops into a swirl-stabilized plasma due to the continuous microwave stimulation. In the low-energy regime, which is below plasma formation, the flame becomes larger and more stable and it moves upstream closer to the burner nozzle when microwaves are absorbed by the flame. As a result of a larger flame the exhaust gas temperature, flame CL and OH PLIF signals are increased as microwave energy is absorbed by the flame.
9.	Ericsson, Niclas (författare) Improving Development of Communication Software in Industrial Control Systems using Simulation 2017 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract In the industrial domain customers expect a product longevity of 10-20 years, with high reliability and availability. Since industrial distributed control systems often are safety critical, aspects such as determinism, low latency and jitter are crucial. More and more industrial systems are becoming connected to the Internet, since end customers are requiring e.g. business intelligence and diagnostic information, anywhere at any time. Industrial systems that traditionally have been isolated are now facing entirely new challenges that will require new competences and ways of working. Introducing a new type of network in the industrial domain is a big investment, with high risks, often lacking known best practices. Time to market with sufficient quality is of high importance. A lot of time is spent on isolated activates, such as, simulations, updating tools, collecting requirements, design, coding, debugging, documentation, creating testbeds, validation and reviews. Therefore, there is a need to improve the efficiency when moving between the research and development phases for several reasons, e.g., integrate innovative research findings into industrial systems, shorten time to market, and improve product quality. This thesis focuses on improving efficiency during research and development of communication software. First, network evaluation methods are studied, and key industrial challenges are identified. For example, despite a huge research effort on network simulators and virtualization, there are still challenges that need to be addressed, in order for increased industrial benefits. Secondly, this thesis propose a flexible communication stack design that supports different run-time behaviors, from real-time operating system to bare-metal systems without an operating system, and different types of communication protocols, from real-time to non-real-time. Finally, this thesis propose a set of key features from network simulators, that are implemented and used as a case study in a research project. These contributions lead to simplification and increased automation, hence reducing the amount of manual work during research and development.
10.	Fagrell Trygg, Nadja, et al. (författare) Reducing or reproducing inequalities in health? : An intersectional policy analysis of how health inequalities are represented in a Swedish bill on alcohol, drugs, tobacco and gambling 2022 Ingår i: BMC Public Health. - : BioMed Central. - 1471-2458. ; 22 Tidskriftsartikel (refereegranskat)abstract Background: According to post-structural policy analyses, policies and interventions aiming at reducing social inequalities have been found to be part in producing and reifying such inequalities themselves. Given the central role of health inequalities on the public health policy agenda globally it seems important to examine the way policy on health inequalities may potentially counteract the goal of health equity. The aim of this intersectional policy analysis, was to critically analyze the representation of health inequalities in a government bill proposing a national strategy on alcohol, drugs, tobacco and gambling, to examine its performative power, and to outline alternative representations.Method: A post-structural approach to policy analysis was combined with an intersectional framework. The material was analyzed through an interrogating process guided by the six questions of the “What’s the problem represented to be?” (WPR) approach. Thus, the underlying assumptions of the problem representation, its potential implications and historical background were explored. In a final step of the analysis we examined our own problem representations.Results: The recommendations found in the gender and equity perspective of the bill represented the problem of health inequalities as a lack of knowledge, with an emphasis on quantitative knowledge about differences in health between population groups. Three underlying assumptions supporting this representation were found: quantification and objectivity, inequalities as unidimensional, and categorization and labelling. The analysis showed how the bill, by opting into these partly overlapping assumptions, is part of enacting a discourse on health inequalities that directs attention to specific subjects (e.g., vulnerable) with special needs (e.g., health care), in certain places (e.g., disadvantaged neighborhoods). It also showed how underlying processes of marginalization are largely neglected in the bill due to its focus on describing differences rather than solutions. Finally, we showed how different intersectional approaches could be used to complement and challenge this, potentially counteractive, problem representation.Conclusions: The problem representation of health inequalities and its underlying assumptions may have counteractive effects on health equity, and even though some of its strengths are raised, it seems to be profoundly entangled with a system resisting the kind of change that the bill itself advocates for. If carefully used, intersectionality has the potential to support a more comprehensive and inclusive equality-promoting public health policy and practice.
11.	Garcia, Johan, 1970-, et al. (författare) Deterministic network emulation using KauNetEm 2016 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract This paper presents KauNetEm, an extension to the Linux-based NetEm emulator that provides deterministic network emulation. KauNetEm enables precise and repeatable placement of NetEm emulation effects, a functionality that canconsiderably simplify several aspects of protocol evaluation. KauNetEm can be instructed to drop specific packets, apply a configurable delay or other emulation effects at predefinedpoints in time. The motivation for deterministic emulation, the overall design of KauNetEm, and usage examples are provided
12.	Garcia, Johan, 1970-, et al. (författare) Evaluating and Modeling 5G MPTCP Performance 2022 Ingår i: International Conference on Wireless and Mobile Computing, Networking and Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665469753 ; , s. 406-411 Konferensbidrag (refereegranskat)abstract Multipath connectivity and aggregation of multiple communication links is actively being researched with the aim to achieve higher throughput and lower latency. In this work we perform an emulation-based evaluation of the relative goodput of MPTCP and TCP in a 5G usage context. A large range of path capacity and delay conditions is explored, for both the primary and secondary paths, with over 2000 different configurations evaluated. Evaluations are performed over eight combinations of MPTCP schedulers and congestion controls. The results show that MPTCP running over two links provide lower goodput than TCP over a single link for the majority of cases. Asymmetry in link conditions is in many cases a major complication for the MPTCP scheduler. To examine the predictability of poor performance, and to obtain further insight on the structure of this phenomena, we perform regression modeling of the relative good put. In addition to the traditional approaches of Linear Regression and Random Forest, we also employ Sym-bolic Regression to obtain mathematical expressions capable of providing insight on the path conditions most contributing to poor MPTCP performance. Such regression expressions can be informative when evaluating different schedulers or link aggregation approaches.
13.	Garcia, Johan, 1970-, et al. (författare) Getting What You Want When You Want It : Deterministic Network Emulation 2016 Konferensbidrag (refereegranskat)abstract This paper presents KauNetEm, an extension to the Linux-based NetEm emulator that provides deterministic network emulation. KauNetEm enables precise and repeatable placement of NetEm emulation effects, a functionality that can considerably simplify several aspects of protocol evaluation. KauNetEm can be instructed to drop specific packets, apply a configurable delay or other emulation effects at predefined points in time. The motivation for deterministic emulation, the overall design of KauNetEm, and usage examples are provided.
14.	Garcia, Johan, 1970-, et al. (författare) KauNet : Design and Usage 2008 Rapport (övrigt vetenskapligt/konstnärligt)abstract KauNet is an emulation system that allows deterministic placement of packet losses and bit-errors as well as more precise control over bandwidth and delay changes. KauNet is an extension to the well-known Dummynet emulator in FreeBSD and allows the use of pattern and scenario files to increase control and repeatability. This report provides a comprehensive description of the usage of KauNet, as well as a technical description of the design and implementation of KauNet.
15.	Garcia, Johan, et al. (författare) KauNet: A Versatile and Flexible Emulation System 2008 Konferensbidrag (refereegranskat)
16.	Garcia, Johan, et al. (författare) The Effect of Packet Loss on the Response Times of Web Services 2007 Ingår i: Proceedings of 3rd International Conference on Web Information Systems and Technologies (WebIST2007). - : INSTICC Press. - 9789728865771 Konferensbidrag (refereegranskat)
17.	Grinnemo, Karl-Johan, 1968-, et al. (författare) Deliverable D3.1 - Initial Report on the Extended Transport System 2017 Rapport (refereegranskat)abstract The NEAT System offers an enhanced API for applications that disentangles them from the actual transport protocol being used. The system also enables applications to communicate their service requirements to the transport system in a generic, transport-protocol independent way. Moreover, the architecture of the NEAT System promotes the evolution of new transport services. Work Package 3 (WP3) enhances and extends the core parts of the NEAT Transport. Efforts have been devoted to developing transport-protocol mechanisms that enable a wider spectrum of NEAT Transport Services, and that assist the NEAT System in facilitating several of the commercial use cases. Work has also started on the development of optimal transport-selection mechanisms; mechanisms that enable for the NEAT System to make optimal transport selections on the basis of application requirements and network measurements. Lastly, another research activity has been initiated on how to use SDN to signal application requirements to routers, switches, and similar network elements. This document provides an initial report on all these WP3 activities—both on completed and on near-termplanned work.
18.	Grinnemo, Karl-Johan, 1968-, et al. (författare) Deliverable D3.2 - Final Report on Transport Protocol Enhancements 2017 Rapport (refereegranskat)abstract This deliverable provides a final report on the work on transport protocol enhancements done inWork Package 3. First, we report on the extensions made to the SCTP protocol that turn it into a viable alternative to TCP and allow to deliver a lower-latency transport service. Next, we describe our work to develop a framework for providing a deadline-aware, less-than-best-effort transport service, targeting background traffic and thus addressing requirements on NEAT from the EMC use case. We also present our efforts to design and implement a latency-aware scheduler for MPTCP, which enables NEAT to offer a transport service that meets the needs of latency-sensitive applications, and that efficiently utilises available network resources. Lastly, this document informs on our work on coupled congestion control for TCP, a mechanism that treats a bundle of parallel TCP flows between the same pair of hosts as a single unit. By efficiently multiplexing concurrent TCP flows, our coupled congestion control alleviates the effects of queueing, and tends to result in a more efficient usage of available bandwidth, where the flows’ aggregate capacity share can be apportioned based on application preferences.
19.	Grinnemo, Karl-Johan, 1968-, et al. (författare) Deliverable D3.3 - Extended Transport System and Transparent Support of Non-NEAT Applications 2017 Rapport (refereegranskat)abstract This deliverable summarises and concludes our work in Work Package 3 (WP3) to extend the transport services provided by the NEAT System developed in Work Package 2, and to enable non-NEAT applications to harness the transport services offered by NEAT. We have demonstrated how a policy- and information-based selection of transport protocol by NEAT could provide a more efficient transport service for web applications. The information on which NEAT makes its transport selection decisions resides in the Characteristics Information Base (CIB). The CIB is populated by various CIB sources, and in WP3 we have designed, implemented, and evaluated various CIB sources, including meta data from mobile broadband networks, passive measurements, IPv6 Provisioning Domain protocols and the Happy Eyeballs mechanism, which caches the outcome of its connection attempts. A key property of NEAT is that it not only “vertically” decouples applications from transport protocols, but also “horizontally”. Particularly, it enables applications to harness information about resource availability and policies from Software Defined Networking (SDN) controllers in managed networks, without these applications actually being SDN-aware. To extend the use of NEAT to non-NEAT applications, we have implemented a BSDcompatible sockets API on top of NEAT and a NEAT proxy that intercepts and replaces standard TCP connections with NEAT flows, i.e., with the transport solutions deemed most appropriate by NEAT.We have also proposed a way for non-NEAT applications to make use of NEAT through the deployment of NEAT-enabled virtual appliances in SDN-controlled networks: connections from these applications are routed via an SDN-controlled proxy that terminates the original connection and replaces it with a NEAT-selected connection.
20.	Grinnemo, Karl-Johan, 1968-, et al. (författare) NEAT - A New, Evolutive API and Transport-Layer Architecture for the Internet 2016 Ingår i: 12th Swedish National Computer Networking Workshop (SNCNW 2016), Sundsvall, Sweden.. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract There is a growing concern that the Internet trans- port layer has become ossified in the face of emerging novel applications, and that further evolution has become very difficult. This paper identifies requirements for a new transport layer and then proposes a conceptual architecture, the NEAT system, that we believe is both flexible and evolvable. Applications interface the NEAT system through an enhanced user API that decouples them from the operation of the transport protocols and the network features being used. In particular, applications provide the NEAT system with information about their traffic requirements, pre- specified policies, and measured network conditions. On the basis of this information, the NEAT system establishes and configures appropriate connections.
21.	Grinnemo, Karl-Johan, 1968-, et al. (författare) Towards a Flexible Internet Transport Layer Architecture 2016 Ingår i: The 22nd IEEE International Symposium on Local and Metropolitan Area Networks (LANMAN), Rome, Italy, June 2015. - : IEEE. - 9781467398824 Konferensbidrag (refereegranskat)abstract There is a growing concern that the Internet trans- port layer has stagnated and become less adaptive to the requirements imposed by new applications, and that further evolution has become very difficult. This is because a fundamental assumption no longer holds: it can no longer be assumed that the transport layer is only in the scope of end-hosts. The success of TCP and UDP and the ubiquity of middleboxes have led to ossification of both the network infrastructure and the API presented to applications. This has led to the development of workarounds, and a range of point solutions that fail to cover many facets of the problem. To address this issue, this paper identifies requirements for a new transport layer and then proposes a conceptual architecture that we argue is both flexible and evolvable. This new architecture requires that applications interface to the transport at a higher abstraction level, where an application can express communication preferences via a new richer API. Protocol machinery can use this information to decide which of the available transport protocols is used. By placing the protocol machinery in the transport layer, the new architecture can allow for new protocols to be deployed and enable evolution of the transport layer.
22.	Habtegebreil, Haile, et al. (författare) Impact of TCP BBR on CUBIC trafﬁc : a mixed workload evaluation 2018 Konferensbidrag (refereegranskat)abstract A recently proposed congestion control algorithm (CCA) called BBR (Bottleneck Bandwidth and Round-trip propagation time) has shown a lot of promise in avoiding some of the problems that have plagued loss-based CCAs. Nevertheless, deployment of a new alternative algorithm requires a thorough evaluation of the effect of the proposed alternative on established transport protocols like TCP CUBIC. Furthermore, evaluations that consider the heterogeneity of Internet trafﬁc sizes would provide a useful insight into the deployability of an algorithm that introduces sweeping changes across multiple algorithm components. Yet, most evaluations of BBR’s impact and competitive fairness have focused on the steady-state performance of large ﬂows. This work expands on previous studies of BBR by evaluating BBR’s impact when the trafﬁc consists of ﬂows of different sizes. Our experiments show that under certain circumstances BBR’s startup phase can result in a signiﬁcant reduction of the throughput of competing large CUBIC ﬂows and the utilization of the bottleneck link. In addition, the steady-state operation of BBR can have negative impact on the performance of bursty ﬂows using loss-based CCAs over bottlenecks with buffer sizes as high as two times the bandwidth-delay product.
23.	Haile, Habtegebreil Kassaye, 1986- (författare) Achieving Low Latency and High Throughput over Cellular Internet Connections 2023 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The continuous increase in the number and type of Internet services and their requirements for improved QoS has motivated the steady evolution of cellular networks towards the current fifth generation (5G) systems. However, updating the network to 5G is insufficient to satisfy application requirements since performance limitations can also exist in the transport used by the applications. Legacy transport protocols and congestion control algorithms (CCAs) are not suitable for applications with requirements for both throughput and delay. This mismatch has inspired new transport protocols and CCAs, such as QUIC and BBR. Nevertheless, cellular networks present challenges that can make it difficult for newly proposed CCAs to achieve consistent throughput and delay. The main focus of this thesis is enhancing transport protocols and CCAs to achieve lower delay and high throughput in cellular networks. An extensive review of available end-to-end CCAs for cellular networks is provided in this thesis, along with the challenges and future directions for research. The delivery rate at a receiver is an important quantity that has found increased use in modern CCAs, and in this thesis, we propose and validate a Kalman-filter-based technique to obtain a steady estimate of the delivery rate for a cellular bottleneck. This thesis also proposes an extension to the QUIC protocol to make receiver-side delivery rate estimates available to the sender CCAs. Using the proposed rate estimation method and extension to the QUIC protocol, this thesis proposes modifications to the recently proposed CCAs BBR and Copa. The proposed modifications are evaluated over real cellular networks and through extensive trace-based emulations. The modified BBR results in lower packet delays with similar throughput to standard BBR in cellular bottlenecks. On the other hand, the modification to Copa strives to provide a more consistent and predictable delay performance across different cellular bottlenecks.
24.	Haile, Habtegebreil Kassaye, et al. (författare) Copa-D: Delay Consistent Copa for Dynamic Cellular Networks 2023 Ingår i: 2023 Joint European Conference on Networks and Communications and 6G Summit, EuCNC/6G Summit. - : IEEE. ; , s. 508-513 Konferensbidrag (refereegranskat)abstract The lack of consideration for application delay requirements in standard loss-based congestion control algorithms (CCAs) has motivated the proposal of several alternative CCAs. As such, Copa is one of the most recent and promising CCAs, and it has attracted attention from both academia andindustry. The delay performance of Copa is governed by amostly static latency-throughput tradeoff parameter, δ. However,a static δ parameter makes it difficult for Copa to achieve consistent delay and throughput over a range of bottleneck bandwidths. In particular, the coexistence of 4G and 5G networks and the wide range of bandwidths experienced in NG-RANs can result in inconsistent CCA performance. To this end, we propose a modification to Copa, Copa-D, that dynamically tunes δ to achieve a consistent delay performance. We evaluate the modification over emulated fixed, 4G, and 5G bottlenecks. The results show that Copa-D achieves consistent delay with minimal impact on throughput in fixed capacity bottlenecks. Copa-D also allows a more intuitive way of specifying the latency-throughput tradeoff and achieves more accurate and predictable delay invariable cellular bottleneck.
25.	Haile, Habtegebreil Kassaye, et al. (författare) End-to-end congestion control approaches for high throughput and low delay in 4G/5G cellular networks 2021 Ingår i: Computer Networks. - : Elsevier. - 1389-1286 .- 1872-7069. ; 186, s. 1-22 Tidskriftsartikel (refereegranskat)abstract Cellular networks have evolved to support high peak bitrates with low loss rates as observed by the higherlayers. However, applications and services running over cellular networks are now facing other difficult congestion-related challenges, most notably a highly variable link capacity and bufferbloat. To overcome theseissues and improve performance of network traffic in 4G/5G cellular networks, a number of in-network and end-to-end solutions have been proposed. Fairness between interacting congestion control algorithms (CCAs) has played an important role in the type of CCAs considered for research and deployment. The placement of content closer to the user and the allocation of per-user queues in cellular networks has increased the likelihood of a cellular access bottleneck and reduced the extent of flow interaction between multiple users. This has resulted in renewed interest in end-to-end CCAs for cellular networks by opening up room for researchand exploration. In this work, we present end-to-end CCAs that target a high throughput and a low latency over highly variable network links, and classify them according to the way they address the congestion control. The work also discusses the deployability of the algorithms. In addition, we provide insights into possible future research directions, such as coping with a higher degree of variability, interaction of CCAs in as hared bottleneck, and avenues for synergized research, such as CCAs assisted by software defined networking and network function virtualization. We hope that this work will serve as a starting point for systematically navigating through the expanding number of cellular CCAs.
26.	Haile, Habtegebreil Kassaye, et al. (författare) Evaluation of the Impact of TCP BBR Startup on CUBIC Traffic 2018 Ingår i: The Fourteenth Swedish National Computer Networking Workshop (SNCNW) 2018. Konferensbidrag (övrigt vetenskapligt/konstnärligt)
27.	Haile, Habtegebreil Kassaye, et al. (författare) Performance of QUIC congestion control algorithms in 5G networks 2022 Ingår i: Proceedings of the ACM SIGCOMM 2022 Workshop on 5G and Beyond Network Measurements, Modeling, and Use Cases - Part of SIGCOMM 2022<em></em>. - New York, NY, USA : Association for Computing Machinery (ACM). ; , s. 15-21 Konferensbidrag (refereegranskat)abstract The deployment of the next generation of cellular networks (5G) is expanding to enable new services and improve the quality of existing ones. Despite the benefits of 5G networks, they also present new challenges for the performance of classical and recently-proposed congestion control algorithms (CCAs), e.g., Bottleneck bandwidth and round-trip propagation time (BBR) and Copa. Despite their successful adoption in the Internet, BBR has been shown to overestimate the bottleneck bandwidth in cellular networks, and Copa has not been independently tested on a similar scale and detail as BBR in cellular networks. In this work, we compare the performance of these fairly recent CCAs as well as the widely deployed CUBIC CCA, and a modification to BBR for cellular networks (RBBR) at 5G rates. The evaluation is performed using the emerging QUIC protocol and uses both emulations and live experiments. Our results show that in 5G networks, CUBIC, BBR, and Copa suffer from significant bufferbloat, longer packet delays, and lower throughput, respectively. We also observe that in cases where the bottleneck is largely in the 5G link, RBBR can offer a significant delay reduction compared to BBR and CUBIC.
28.	Haile, Habtegebreil Kassaye, et al. (författare) Rate Change Detection in Stationary Cellular Nodes 2019 Ingår i: Proceedings of the Fifteenth Swedish National Computer NetworkingWorkshop (SNCNW), Luleå, Sweden. 4-5 June. Konferensbidrag (refereegranskat)abstract An increasing number of cellular congestion controlalgorithms (CCAs) are relying on measurements of the deliveryrate observed at the receiver. Accordingly, early detection ofchanges in the receiver’s rate would improve the performanceof such algorithms. Rate measurements over short time intervalscould allow fast detection of change in the rate observed bythe upper layers of a cellular receiver. However, upper layerrate measurements for cellular receivers over a short time scaleproduce unreliable results due to the effect of underlying lowerlayer mechanisms. In this paper, we introduce a rate estimationapproach that reduces the variability observed in short timescale receiver rate measurements and allows faster rate changedetection.
29.	Haile, Habtegebreil Kassaye, et al. (författare) Rate Measurement Over Short Time Scales inStationary Cellular Receivers 2019 Ingår i: Proceedings of the 3rd Workshop on Mobile Network Measurement (MNM 2019), Paris, France, June 2019. Konferensbidrag (refereegranskat)abstract An increasing number of cellular congestion controlalgorithms (CCAs) are relying on measurements of the deliveryrate observed at the receiver. Accordingly, early detection ofchanges in the receiver’s rate would improve the performanceof such algorithms. Rate measurements over short time intervalscould allow fast detection of change in the rate observed bythe upper layers of a cellular receiver. However, for cellularreceivers, upper-layer rate measurements over short time scalesproduce unreliable results due to the effect of underlying lowerlayer mechanisms such as scheduling and retransmissions. In thispaper, we introduce a rate estimation approach that reduces thevariability observed in short time scale receiver rate measurementsand allows faster rate change detection. We also integratean adaptive mechanism to improve online measurements overdifferent time scales.
30.	Haile, Habtegebreil Kassaye, et al. (författare) RBBR: A Receiver-driven BBR in QUIC for Low-latency in Cellular Networks 2022 Ingår i: IEEE Access. - : IEEE. - 2169-3536. ; 10, s. 18707-18719 Tidskriftsartikel (refereegranskat)abstract BBR is a promising new congestion control algorithm (CCA) that has been shown to result in significantly lower latency compared to conventional loss-based CCAs. However, in cellular networks, where there is a high variability in the available rate, BBR does not perform as well as expected. In such scenarios, BBR tends to overestimate the available capacity and create queues that cause longer packet delays. In this work, we propose Receiver-driven BBR (RBBR), a modified version of BBR that uses rate estimates made at the receiver side rather than at the sender side. We employ a Kalman filter to make a more accurate estimate of the available bandwidth, and we implement the algorithm in QUIC. An evaluation of the proposed CCA is done through extensive 4G trace-based emulations, real 4G network tests and mmWave trace-based emulations representing a 5G scenario. The results show that RBBR is able to achieve an RTT reduction of up to 80\% with a worst-case throughput loss of about 30\%. The results also show that in real 4G networks, RBBR flows experience a more predictable and consistent RTT than what BBR flows do.
31.	Haile, Habtegebreil Kassaye, et al. (författare) WIP: Leveraging QUIC for a Receiver-driven BBR for Cellular Networks 2021 Ingår i: 2021 IEEE 22nd International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665422635 ; , s. 252-255 Konferensbidrag (refereegranskat)abstract Cellular networks are continuously evolving to allow improved throughput and low latency performance for applications. However, it has been shown that, due to buffer over-provisioning, TCP’s standard loss-based congestion control algorithms (CCAs) can cause long delays in cellular networks. The QUIC transport protocol and the Bottleneck Bandwidth and Round-trip propagation time (BBR) congestion control are both proposed in response to shortcomings observed in TCP and loss-based CCAs. Despite its notable advantages, BBR can experience suboptimal delay performance in cellular networks due to one of its underlying design choices: the maximum bandwidth filter at the sender. In this work, we leverage QUIC’s extensibility to enhance BBR. Instead of using the ACK rate observed at the sender side, we apply a more fitting delivery rate calculated at the receiver. Our 5G-trace-based emulation experiments in CloudLab suggest that our modified QUIC could significantly improve latency without any notable effect on the throughput: In particular, in some of our experiments, we observe up to 39% reduction of the round-trip time (RTT) with a worst case throughput reduction of 2.7%.
32.	Hall, Tomas, et al. (författare) Performance Evaluation of KauNet in Physical and Virtual Emulation Environments 2012 Rapport (övrigt vetenskapligt/konstnärligt)abstract Evaluation of applications and protocols in the context of computer networking is often necessary to determine the efficiency and level of service they can provide. In practical testing, three different options are available for the evaluation; using a physical network as a testbed, using an emulator to simplify the infrastructure, or using a simulator to remove reliance on infrastructure entirely. As a real network is costly and difficult or even impossible to create for every scenario, emulation and simulation is often used to approximate the behavior of a network with considerably less resources required. However, while a simulator is limited only by the time required to perform the simulation, an emulator is also limited by the hardware and software used. It is therefore important to evaluate the performance of the emulator itself, to determine its ability to emulate the desired network topologies.The focus of this document is the KauNet emulator, an extension of Dummynet that adds several new features, primarily deterministic emulation of various network characteristics through the use of pre-generated patterns. A series of tests were per- formed using a testbed with KauNet in both physical and virtual environments, as well as a hybrid environment with both physical and virtual machines. While virtualization greatly increases the flexbility and utilization of resources compared to a pure physical setup, it may also reduce the overall performance and accuracy of the emulation.From the results achieved, KauNet performs well in a physical environment, with a high degree of accuracy even at high traffic loads. Virtualization on the other hand, clearly introduces several issues with both processing and packet loss that may make it undesirable for use in experiments, although it may still be sufficient for scenarios where the requirements for accuracy are lower. The hybrid environment represents a compromise, with both performance and flexibility midway between the physical and fully virtualized testbed.
33.	Hurtig, Per, 1980-, et al. (författare) A NEAT Approach to Mobile Communication 2017 Ingår i: MobiArch ’17 Proceedings of the Workshop on Mobility in the Evolving Internet Architecture. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450350594 ; , s. 7-12 Konferensbidrag (refereegranskat)abstract The demands for mobile communication is ever increasing. Mobile applications are increasing both in numbers and in heterogeneity of their requirements, and an increasingly diverse set of mobile technologies are employed. This creates an urgent need for optimizing end-to-end services based on application requirements, conditions in the network and available transport solutions; something which is very hard to achieve with today's Internet architecture. In this paper, we introduce the NEAT transport architecture as a solution to this problem. NEAT is designed to offer a flexible and evolvable transport system, where applications communicate their transport-service requirements to the NEAT system in a generic, transport-protocol independent way. The best transport option is then configured at run time based on application requirements, network conditions, and available transport options. Through a set of real life mobile use case experiments, we demonstrate how applications with different properties and requirements could employ the NEAT system in multi-access environments, showing significant performance benefits as a result.
34.	Hurtig, Per, et al. (författare) Analys av trafiksäkerhetsutvecklingen 2022 : Målstyrning av trafiksäkerhetsarbetet mot etappmålen 2030 2023 Rapport (övrigt vetenskapligt/konstnärligt)abstract Det svenska trafiksäkerhetsarbetet utgår från Nollvisionen och etappmål på vägen dit. Det nuvarande etappmålet för vägtrafiken innebär en halvering av antalet omkomna, från 266 (medelvärde 20172019), till max 133 omkomna år 2030. Etappmålet innebär också att antalet allvarligt skadade i vägtrafiken ska reduceras med 25 procent utifrån ett motsvarande utgångsvärde.I denna rapport redovisas och analyseras utvecklingen av säkerheten i vägtrafiken utifrån utpekade indikatorer och antalet omkomna. Antalet allvarligt skadade redovisas inte då en ny metod för bortfallsuppräkning av antalet allvarligt skadade tas fram under 2023. Utöver beslutade nationella etappmål finns även ett etappmål på EUnivå som innebär en halvering av antalet omkomna till 2030, jämfört med 2019.
35.	Hurtig, Per, et al. (författare) Analysis of road safety trends 2022 : Management by objectives for road safety work towards the 2030 interim targets 2023 Rapport (övrigt vetenskapligt/konstnärligt)abstract Swedish road safety work is based on Vision Zero and designated interim targets to track progress towards its achievement. The current interim target for road safety is to halve the number of fatalities from 266 (the average annual number 20172019) to a maximum of 133 fatalities in 2030. The interim target also specifies that the number of seriously injured on the roads is to be reduced by 25 per cent from a corresponding number.This report describes and analyses current road safety trends in terms of road safety performance indicators and the numbers of fatalities. The number of seriously injured is not reported, as a new method for non-response compensation of the number of seriously injured is being developed in 2023. In addition to the adopted national interim targets there is also an interim target at the EU level that specifies a halving, by 2030, of the number of fatalities recorded in 2019.
36.	Hurtig, Per, 1980-, et al. (författare) Early Retransmit for TCP and Stream Control Transmission Protocol (SCTP) 2010 Ingår i: Internet Engineering Task Force. - : Internet Engineering Task Force. - 2070-1721. ; , s. 1-15 Tidskriftsartikel (refereegranskat)abstract This document proposes a new mechanism for TCP and Stream Control Transmission Protocol (SCTP) that can be used to recover lost segments when a connection's congestion window is small. The "Early Retransmit" mechanism allows the transport to reduce, in certain special circumstances, the number of duplicate acknowledgments required to trigger a fast retransmission. This allows the transport to use fast retransmit to recover segment losses that would otherwise require a lengthy retransmission timeout
37.	Hurtig, Per, et al. (författare) Emulation Support for Advanced Packet Reordering Models 2010 Ingår i: 2010 IEEE International Conference on Communications. - Cape Town, South Africa : IEEE Communications Society. - 9781424464043 Konferensbidrag (refereegranskat)abstract From being regarded as a pathological event, packet reordering is now considered to be naturally prevalent within the Internet. When packets are reordered, the performance of transport protocols like TCP can be severely hurt. To overcome performance problems a number of mitigations have been proposed. Common for most proposals is, however, the lack of evaluations using real protocol implementations and good models of packet reordering. In this paper we highlight the need for detailed reordering models, and implement support for such models in the KauNet network emulator. To demonstrate the importance of using detailed models we present an experimental example.
38.	Hurtig, Per, 1980-, et al. (författare) Enhanced Metric Caching for Short TCP Flows 2012 Ingår i: Proceedings of the IEEE International Conference on Communications (ICC 2012). - : IEEE Press. - 9781457720512 - 9781457720529 ; , s. 1209-1213 Konferensbidrag (refereegranskat)abstract Internet-based applications that require low latency are becoming more common. Such applications typically generate traffic consisting of short, or bursty, TCP flows. As TCP, instead, is designed to optimize the throughput of long bulk flows there is an apparent mismatch. To overcome this, a lot of research has recently focused on optimizing TCP for short flows as well. In this paper, we identify a performance problem for short flows caused by the metric caching conducted by the TCP control block interdependence mechanisms. Using this metric caching, a single packet loss can potentially ruin the performance for all future flows to the same destination by making them start in congestion avoidance instead of slow-start. To solve this, we propose an enhanced selective caching mechanism for short flows. To illustrate the usefulness of our approach, we implement it in both Linux and FreeBSD and experimentally evaluate it in a real test-bed. The experiments show that the selective caching approach is able to reduce the average transmission time of short flows by up to 40%.
39.	Hurtig, Per, 1980-, et al. (författare) Enhancing SCTP Loss Recovery: An Experimental Evaluation of Early Retransmit 2008 Ingår i: Computer Communications. - Amsterdam : Elsevier. - 0140-3664 .- 1873-703X. ; 31:16, s. 3778-3788 Tidskriftsartikel (refereegranskat)abstract To reduce cost and provide more flexible services, telecommunication operators are currently replacing traditional circuit-switched telephony networks with packet-switched IP networks. To support the stringent requirements of telephony signaling (SS7), the SIGTRAN working group of the IETF specified the transport protocol SCTP. SCTP was developed to overcome a number of problems that follow from using TCP for signaling transport. However, the design of SCTP was to a great extent still based on TCP, and some problems related to signaling transport were inherited. For example, the loss recovery mechanisms in SCTP are almost identical to those of TCP. This is a problem as signaling traffic has stringent requirements on timely message delivery. TCP was not designed to meet stringent requirements on timely message delivery, and therefore the loss recovery was not optimized for it. To optimize SCTP’s loss recovery for signaling traffic, we consider the loss recovery enhancement early retransmit. To make early retransmit even better suited for signaling traffic we propose a packet-based version, which was also recently included in the early retransmit specification. By experimentally evaluating this algorithm, we show that the packet-based early retransmit algorithm, in some cases, can reduce SCTP’s loss recovery time by 62%.
40.	Hurtig, Per, 1980-, et al. (författare) Impact of TCP BBR on CUBIC Traffic : A mixed workload evaluation 2018 Ingår i: Proceedings of the 30th International Teletraffic Congress, ITC 2018. - : IEEE. - 9780988304550 ; , s. 218-226 Konferensbidrag (refereegranskat)abstract A recently proposed congestion control algorithm (CCA) called BBR (Bottleneck Bandwidth and Round-trip propagation time) has shown a lot of promise in avoiding some of the problems that have plagued loss-based CCAs. Nevertheless, deployment of a new alternative algorithm requires a thorough evaluation of the effect of the proposed alternative on established transport protocols like TCP CUBIC. Furthermore, evaluations that consider the heterogeneity of Internet traffic sizes would provide a useful insight into the deployability of an algorithm that introduces sweeping changes across multiple algorithm components. Yet, most evaluations of BBR's impact and competitive fairness have focused on the steady-state performance of large flows. This work expands on previous studies of BBR by evaluating BBR's impact when the traffic consists of flows of different sizes. Our experiments show that under certain circumstances BBR's startup phase can result in a significant reduction of the throughput of competing large CUBIC flows and the utilization of the bottleneck link. In addition, the steady-state operation of BBR can have negative impact on the performance of bursty flows using loss-based CCAs over bottlenecks with buffer sizes as high as two times the bandwidth-delay product.
41.	Hurtig, Per, 1980-, et al. (författare) Improved Loss Detection for Signaling Traffic in SCTP 2008 Ingår i: IEEE International Conference on Communications (ICC 08). - : IEEE. - 9781424420759 ; , s. 5886-5891 Konferensbidrag (refereegranskat)abstract The Stream Control Transmission Protocol (SCTP) was designed by the IETF as a viable solution for transportation of signaling traffic within IP-based networks. Signaling traffic is different from ordinary TCP bulk traffic in many ways. One example is that the requirement of timely delivery usually is much stricter. However, the management of the SCTP retransmission timer is not optimally designed considering this requirement. Basically, the management algorithm, unnecessarily, extends the time needed for loss detection. This paper presents a new management algorithm that is able to maintain a correct state of the retransmission timer, which eliminates this particular problem. In addition, the paper also compares the performance of the two management algorithms in an emulated signaling environment, using the lksctp implementation of SCTP. The results show that the proposed algorithm is able to provide significant reductions in loss recovery time. In some cases, the time needed to recover from packet loss is reduced with as much as 43%.
42.	Hurtig, Per, 1980- (författare) Improving the Timeliness of SCTP Message Transfers 2008 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Due to the cheap and flexible framework that the underlying IP-technology of the internet provides, IP-networks are becoming popular in more and more contexts. For instance, telecommunication operators have started to replace the fixed legacy telephony networks with IP-networks. To support a smooth transition towards IP-networks, the Stream Control Transmission Protocol (SCTP) was standardized. SCTP is used to carry telephony signaling traffic, and solves a number of problems that would have followed from using the Transmission Control Protocol (TCP) in this context. However, the design of SCTP is still heavily influenced by TCP. In fact, many protocol mechansisms in SCTP are directly inherited from TCP. Unfortunately, many of these mechanisms are not adapted to the kind of traffic that SCTP is intended to transport: time critical message-based traffic, e.g. telephony signaling.In this thesis we examine, and adapt some of SCTP's mechanisms to more efficiently transport time critical message-based traffic. More specifically, we adapt SCTP's loss recovery and message bundling for timely message transfers. First, we propose and experimentally evaluate two loss recovery mechanisms: a packet-based Early Retransmit algorithm, and a modified retransmission timeout management algorithm. We show that these enhancements can reduce loss recovery times with at least 30-50%, in some scenarios. In addition, we adapt the message bundling of SCTP to better support timely message delivery. The proposed bundling algorithm can in some situations reduce the transfer time of a message with up to 70%.In addition to these proposals we have also indentified and reported mistakes in some of the most popular SCTP implementations. Furthermore, we have continously developed the network emulation software KauNet to support our experimental evaluations.
43.	Hurtig, Per, 1980-, et al. (författare) Loss Recovery in Short TCP/SCTP Flows 2006 Rapport (övrigt vetenskapligt/konstnärligt)abstract The Transmission Control Protocol (TCP) has been the dominant transport protocol within IP-based networks for many years, mainly due to the reliability it provide to its users and the congestion control it employs. However, as the amount of signaling traffic within IP-based networks have increased significantly in recent years, it has become clear that TCP is not suited for this kind of traffic. In order to meet the requirements of signaling traffic the Stream Control Transmission Protocol (SCTP) was developed by the Internet Engineering Task Force (IETF). SCTP is heavily influenced by TCP and is therefore similar to TCP in many ways. One example is the SCTP loss recovery and congestion control mechanisms which are almost identical to those of TCP. The primary purpose of this work is to study the performance and behavior of the TCP/SCTP loss recovery mechanisms for short flows. Using a simple client/server model, we evaluate the performance of these mechanism over a wide range of bandwidths, link delays and packet loss patterns. The experiments evaluate one TCP implementation and two SCTP implementations, and were conducted using network emulation. The experimental results show that there exist strong dependencies between the position of packet loss and the actual transmission time of the corresponding flow. In addition to these dependencies, we also found a number of implementation mistakes in the examined protocol implementations.
44.	Hurtig, Per, 1980-, et al. (författare) Low-Latency Scheduling in MPTCP 2019 Ingår i: IEEE/ACM Transactions on Networking. - : IEEE. - 1063-6692 .- 1558-2566. ; 1, s. 302-315 Tidskriftsartikel (refereegranskat)abstract The demand for mobile communication is continuously increasing, and mobile devices are now the communication device of choice for many people. To guarantee connectivity and performance, mobile devices are typically equipped with multiple interfaces. To this end, exploiting multiple available interfaces is also a crucial aspect of the upcoming 5G standard for reducing costs, easing network management, and providing a good user experience. Multi-path protocols, such as multi-path TCP (MPTCP), can be used to provide performance optimization through load-balancing and resilience to coverage drops and link failures, however, they do not automatically guarantee better performance. For instance, low-latency communication has been proven hard to achieve when a device has network interfaces with asymmetric capacity and delay (e.g., LTE and WLAN). For multi-path communication, the data scheduler is vital to provide low latency, since it decides over which network interface to send individual data segments. In this paper, we focus on the MPTCP scheduler with the goal of providing a good user experience for latency-sensitive applications when interface quality is asymmetric. After an initial assessment of existing scheduling algorithms, we present two novel scheduling techniques: the block estimation (BLEST) scheduler and the shortest transmission time first (STTF) scheduler. BLEST and STTF are compared with existing schedulers in both emulated and real-world environments and are shown to reduce web object transmission times with up to 51% and provide 45% faster communication for interactive applications, compared with MPTCP's default scheduler.
45.	Hurtig, Per, et al. (författare) Message-Based Traffic Control in SCTP 2009 Konferensbidrag (refereegranskat)abstract Telecommunication operators are currently replacing traditional telephony networks with IP-networks. To support telephony signaling requirements in IP-networks, SCTP was standardized. SCTP solves a number of problems that follows from using TCP for signaling transport. However, the design of SCTP is based on inherited TCP mechanisms that were designed for bulk traffic, not for message-based traffic like telephony signaling. In this paper, we discuss the implications of this design, and exemplify the negative effects of it. In particular, we show how to adapt the SCTP message-bundling to work better for message-based traffic. Evaluations of our adapted message bundling show average reductions in message transfer times with as much as 50%, for some scenarios
46.	Hurtig, Per, 1980-, et al. (författare) MPTCP PathFinder : Datacenter Bandwidth Aggregation 2014 Konferensbidrag (refereegranskat)
47.	Hurtig, Per, et al. (författare) Packet Loss Recovery of Signaling Traffic in SCTP 2007 Konferensbidrag (refereegranskat)
48.	Hurtig, Per, 1980-, et al. (författare) Packet Reordering in TCP 2011 Ingår i: Proceedings of the IEEE GLOBECOM Workshop CCNet. - : IEEE Press. - 9781467300384 - 9781467300391 ; , s. 136-141 Konferensbidrag (refereegranskat)abstract Packet reordering is now considered naturally prevalent within complex networks like the Internet. When packets are reordered, the performance of transport protocols like TCP is severely hurt. To overcome performance issues a number of mitigations have been proposed. While evaluations have shown the success of such mitigations, most have not considered realistic scenarios where other impairments are present. Furthermore, most studies only evaluate the performance of long-lived TCP flows, although short-lived flows are the most common. In this paper we evaluate Linux's built-in reordering mitigations and the TCP-NCR proposal using real protocol implementations. The results show that Linux and TCP-NCR are able to provide good protection against reordering when no other impairments are present. For flows that also experience packet loss, the performance is dominated by the negative effect of these losses. Results also indicate that short-lived flows are sensitive to how reordering mitigation is conducted. Linux was able to improve the performance of short flows slightly, while TCP-NCR performed worse than TCP without reordering protection.
49.	Hurtig, Per, 1980-, et al. (författare) Recent Trends in TCP Packet-Level Characteristics 2011 Ingår i: International Conference on Networking and Services (ICNS '11). - Venice/Mestre, Italy : IARIA. - 9781612080062 - 9781612081335 Konferensbidrag (refereegranskat)abstract Up-to-date TCP trafﬁc characteristics are essential for research and development of protocols and applications.This paper presents recent trends observed in 70 measurements on backbone links from 2006 and 2009. First, we provide general characteristics such as packet size distributions and TCP option usage. We conﬁrm previous observations such as the dominance of TCP as transport and higher utilization of TCP options. Next, we look at out-of-sequence (OOS) TCP segments. OOS segments often have negative effects on TCP performance, and therefore require special consideration. While the total fraction of OOS segments is stable in our measurements, we observe a signiﬁcant decrease in OOS due to packet reordering (from 22.5% to 5.2% of all OOS segments). We verify that this development is a general trend in our measurements and not caused by single hosts/networks or special temporal events. Our ﬁndings are surprising as many researchers previously have speculated in an increased amount of reordering.
50.	Hurtig, Per, 1980-, et al. (författare) Reducing Transport Latency using Multipath Protocols 2015 Konferensbidrag (refereegranskat)

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