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1.	Aguiar, Javier, et al. (author) New Data Communication Standards 2012 In: IEEE Communications Magazine. - 0163-6804. ; 50:3, s. 70-71 Journal article (other academic/artistic)
2.	Akbarian, Fatemeh, et al. (author) A Security Framework in Digital Twins for Cloud-based Industrial Control Systems: Intrusion Detection and Mitigation 2021 In: 2021 26th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA ). - 9781728129891 - 9781728129907 Conference paper (peer-reviewed)abstract With the help of modern technologies and advances in communication systems, the functionality of Industrial control systems (ICS) has been enhanced leading toward to have more efficient and smarter ICS. However, this makes these systems more and more connected and part of a networked system. This can provide an entry point for attackers to infiltrate the system and cause damage with potentially catastrophic consequences. Therefore, in this paper, we propose a digital twin-based security framework for ICS that consists of two parts: attack detection and attack mitigation. In this framework we deploy an intrusion detection system in digital domain that can detect attacks in a timely manner. Then, using our mitigation method, we keep the system stable with acceptable performance during the attack. Additionally, we implement our framework on a real testbed and evaluate its capability by subjecting it to a set of attacks.
3.	Akbarian, Fatemeh, et al. (author) Attack Resilient Cloud-Based Control Systems for Industry 4.0 2023 In: IEEE Access. - 2169-3536. ; 11, s. 27865-27882 Journal article (peer-reviewed)abstract In recent years, since the cloud can provide tremendous advantages regarding storage and computing resources, the industry has been motivated to move industrial control systems to the cloud. However, the cloud also introduces significant security challenges since moving control systems to the cloud can enable attackers to infiltrate the system and establish an attack that can lead to damages and disruptions with potentially catastrophic consequences. Therefore, some security measures are necessary to detect these attacks in a timely manner and mitigate their impact. In this paper, we propose a security framework for cloud control systems that makes them resilient against attacks. This framework includes three steps: attack detection, attack isolation, and attack mitigation. We validate our proposed framework on a real testbed and evaluate its capability by subjecting it to a set of attacks. We show that our proposed solution can detect an attack in a timely manner and keep the plant stable, with high performance during the attack.
4.	Akbarian, Fatemeh, et al. (author) Demonstration: A cloud-control system equipped with intrusion detection and mitigation 2021 In: The Conference on Networked Systems (NetSys 2021). Conference paper (peer-reviewed)abstract The cloud control systems (CCs) are inseparable parts of industry 4.0. The cloud, by providing storage and computing resources, allows the controllers to evaluate complex problems that are too computationally demanding to perform locally. However, connecting physical systems to the cloud through the network can provide an entry point for attackers to infiltrate the system and cause damage with potentially catastrophic consequences. Hence, in this paper, we present a demo of our proposed security framework for CCs and demonstrate how it can detect attacks on this system quickly and mitigate them.
5.	Akbarian, Fatemeh, et al. (author) Detecting and Mitigating Actuator Attacks on Cloud Control Systems through Digital Twins 2023 In: The 31st International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2023). - 9798350301076 Conference paper (peer-reviewed)abstract Recently, the industry has been driven to move industrial control systems to the cloud due to the significant advantages it offers in terms of storage and computing resources. However, this shift also brings forth significant security challenges. By moving control systems to the cloud, the potential for attackers to infiltrate the system and launch damaging attacks increases. These attacks can result in severe disruptions and potentially catastrophic consequences. Hence, attack detection and mitigation mechanisms are crucial for cloud control systems. In this paper, we present an approach that leverages the digital twins concept and virtual actuator method to detect and mitigate deception attacks on control signals within cloud control systems. By conducting experiments on a real testbed and subjecting it to a set of attacks, we validate the effectiveness of our solution. Our proposed method successfully detects attacks in a timely manner and keeps the plant stable, with a good performance during the attack.
6.	Akbarian, Fatemeh, et al. (author) Detection and mitigation of deception attacks on cloud-based industrial control systems 2022 In: 25th Conference on Innovation in Clouds, Internet and Networks (ICIN). - 9781728186887 Conference paper (peer-reviewed)abstract In recent years, because the cloud can provide huge advantages regarding storage and computing resources, industry has been motivated to move industrial control systems to the cloud. However, the cloud also introduces major security challenges, since moving control systems to the cloud can enable attackers to infiltrate the system and establish an attack that can lead to damages and disruptions with potentially catastrophic consequences. Therefore, intrusion detection and mitigation mechanisms are crucial for cloud-based industrial control systems. In this paper, we propose a method for detection and mitigation of deception attacks on actuator signals in cloud-based industrial control systems. We validate our solution on a real testbed and evaluate its capability by subjecting it to a set of attacks. Our proposed solution can detect the attack in a timely manner and keep the plant stable, with an acceptable performance during the attack.
7.	Akbarian, Fatemeh, et al. (author) Intrusion Detection in Digital Twins for Industrial Control Systems 2020 In: 2020 International Conference on Software, Telecommunications and Computer Networks (SoftCOM). - 9789532900996 Conference paper (peer-reviewed)abstract Nowadays, the growth of advanced technologies is paving the way for Industrial Control Systems (ICS) and making them more efficient and smarter. However, this makes ICS more connected to communication networks that provide a potential platform for attackers to intrude into the systems and cause damage and catastrophic consequences. In this paper, we propose implementing digital twins that have been equipped with an intrusion detection algorithm. Our novel algorithm is able to detect attacks in a timely manner and also diagnose the type of attack by classification of different types of attacks. With digital twins, which are a new concept in ICS, we have virtual replicas of physical systems so that they precisely mirror the internal behavior of the physical systems. So by placing the intrusion detection algorithm in digital twins, security tests can be done remotely without risking negative impacts on live systems.
8.	Akbarian, Fatemeh, et al. (author) Resilient Cloud Control System: Dynamic Frequency Adaptation via Q-learning 2024 In: 27th Conference on Innovation in Clouds, Internet and Networks (ICIN). - 9798350393774 - 9798350393767 Conference paper (peer-reviewed)abstract Traditional control systems face challenges in managing high data loads and computing power, prompting the evolution of Cloud Control Systems (CCS)-a fusion of Networked Control Systems (NCS) and cloud computing. Despite offering manifold advantages, CCS encounters hurdles in navigating the dynamic cloud environment characterized by fluctuating workloads, rendering static frequency settings inefficient. Moreover, the optimal utilization of cloud resources poses a pivotal challenge within CCS operations. To address these, the paper proposes a resilient CCS by adapting system frequency dynamically. Leveraging Q-learning, the approach measures Round Trip Time (RTT) and system output errors, dynamically adjusting the system's frequency to minimize control costs, optimize performance within the dynamic cloud environment, and achieve resource frugality, minimizing resource usage. Through real testbed experiments, this paper evaluates and analyzes the effectiveness of the proposed method, aiming to establish an adaptive and efficient control framework aligned with evolving cloud dynamics.
9.	Akbarian, Fatemeh, et al. (author) Synchronization in Digital Twins for Industrial Control Systems 2020 Conference paper (peer-reviewed)abstract Digital twins, which are a new concept in industrial control systems (ICS), play a key role in realizing the vision of a smart factory, and they can have different effective use cases. With digital twins, we have virtual replicas of physical systems so that they precisely mirror the internal behavior of the physical systems. Hence, synchronization is necessary to keep the states of digital twins in sync with those of their physical counterparts. Otherwise, their behavior may be different from each other, and it can lead to wrong decisions about the system that can have catastrophic consequences. In this paper, we propose three different architectures for digital twins, and then by investigating their ability to follow the physical system’s behavior, we will determine the best architecture, whose output has the lowest error compared with the physical system’s output.
10.	Ali-Eldin, Ahmed, 1985-, et al. (author) Analysis and characterization of a Video-on-Demand service workload 2015 In: Proceedings of the 6th ACM Multimedia Systems Conference, MMSys 2015. - New York, NY, USA : ACM Digital Library. - 9781450333511 ; , s. 189-200 Conference paper (peer-reviewed)abstract Video-on-Demand (VoD) and video sharing services accountfor a large percentage of the total downstream Internet traf-fic. In order to provide a better understanding of the loadon these services, we analyze and model a workload tracefrom a VoD service provided by a major Swedish TV broad-caster. The trace contains over half a million requests gener-ated by more than 20000 unique users. Among other things,we study the request arrival rate, the inter-arrival time, thespikes in the workload, the video popularity distribution, thestreaming bit-rate distribution and the video duration distri-bution. Our results show that the user and the session ar-rival rates for the TV4 workload does not follow a Poissonprocess. The arrival rate distribution is modeled using a log-normal distribution while the inter-arrival time distributionis modeled using a stretched exponential distribution. Weobserve the “impatient user” behavior where users abandonstreaming sessions after minutes or even seconds of startingthem. Both very popular videos and non-popular videos areparticularly affected by impatient users. We investigate ifthis behavior is an invariant for VoD workloads.
11.	Ali-Eldin, Ahmed, et al. (author) Efficient provisioning of bursty scientific workloads on the cloud using adaptive elasticity control 2012 In: Proceedings of the 3rd workshop on Scientific Cloud Computing Date. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450313407 - 145031340X ; , s. 31-40 Conference paper (peer-reviewed)abstract Elasticity is the ability of a cloud infrastructure to dynamically change theamount of resources allocated to a running service as load changes. We build anautonomous elasticity controller that changes the number of virtual machinesallocated to a service based on both monitored load changes and predictions offuture load. The cloud infrastructure is modeled as a G/G/N queue. This modelis used to construct a hybrid reactive-adaptive controller that quickly reactsto sudden load changes, prevents premature release of resources, takes intoaccount the heterogeneity of the workload, and avoids oscillations. Using simulations with Web and cluster workload traces, we show that our proposed controller lowers the number of delayed requests by a factor of 70 for the Web traces and 3 for the cluster traces when compared to a reactive controller. Ourcontroller also decreases the average number of queued requests by a factor of 3 for both traces, and reduces oscillations by a factor of 7 for the Web traces and 3 for the cluster traces. This comes at the expense of between 20% and 30% over-provisioning, as compared to a few percent for the reactive controller.
12.	Ali-Eldin, Ahmed, 1985-, et al. (author) WAC : A Workload analysis and classification tool for automatic selection of cloud auto-scaling methods Other publication (other academic/artistic)abstract Autoscaling algorithms for elastic cloud infrastructures dynami-cally change the amount of resources allocated to a service ac-cording to the current and predicted future load. Since there areno perfect predictors, no single elasticity algorithm is suitable foraccurate predictions of all workloads. To improve the quality ofworkload predictions and increase the Quality-of-Service (QoS)guarantees of a cloud service, multiple autoscalers suitable for dif-ferent workload classes need to be used. In this work, we intro-duce WAC, a Workload Analysis and Classification tool that as-signs workloads to the most suitable elasticity autoscaler out of aset of pre-deployed autoscalers. The workload assignment is basedon the workload characteristics and a set of user-defined Business-Level-Objectives (BLO). We describe the tool design and its maincomponents. We implement WAC and evaluate its precision us-ing various workloads, BLO combinations and state-of-the-art au-toscalers. Our experiments show that, when the classifier is tunedcarefully, WAC assigns between 87% and 98.3% of the workloadsto the most suitable elasticity autoscaler.
13.	Ali-Eldin, Ahmed, 1985-, et al. (author) Workload Classification for Efficient Auto-Scaling of Cloud Resources 2013 Other publication (other academic/artistic)abstract Elasticity algorithms for cloud infrastructures dynamically change the amount of resources allocated to a running service according to the current and predicted future load. Since there is no perfect predictor, and since different applications’ workloads have different characteristics, no single elasticity algorithm is suitable for future predictions for all workloads. In this work, we introduceWAC, aWorkload Analysis and Classification tool that analyzes workloads and assigns them to the most suitable elasticity controllers based on the workloads’ characteristics and a set of business level objectives.WAC has two main components, the analyzer and the classifier. The analyzer analyzes workloads to extract some of the features used by the classifier, namely, workloads’ autocorrelations and sample entropies which measure the periodicity and the burstiness of the workloads respectively. These two features are used with the business level objectives by the clas-sifier as the features used to assign workloads to elasticity controllers. We start by analyzing 14 real workloads available from different applications. In addition, a set of 55 workloads is generated to test WAC on more workload configurations. We implement four state of the art elasticity algorithms. The controllers are the classes to which the classifier assigns workloads. We use a K nearest neighbors classifier and experiment with different workload combinations as training and test sets. Our experi-ments show that, when the classifier is tuned carefully, WAC correctly classifies between 92% and 98.3% of the workloads to the most suitable elasticity controller.
14.	Amani, Payam, et al. (author) Application of Control Theory to a Commercial Mobile Service Support System 2012 In: International Journal on Advances in Telecommunications. - 1942-2601. ; 5:3&4 Journal article (peer-reviewed)abstract The Mobile Service Support system (MSS), which Ericsson AB develops, handles the setup of new subscribers and services into a mobile network. Experience from deployed systems show that traffic monitoring and control of the system will be crucial for handling overload situations that may occur at sudden traffic surges. In this paper we identify and explore some important control challenges for this type of systems. Further, we present analysis and experiments showing some advantages of proposed solutions. First, we develop a load-dependent server model for the system, which is validated in testbed experiments. Further, we propose a control design based on the model, and a method for estimation of response times and arrival rates. The main contribution of this paper is that we show how control theory methods and analysis can be used for commercial telecom systems. Parts of our results have been implemented in commercial products, validating the strength of our work.
15.	Amani, Payam, et al. (author) Multi-step ahead response time prediction for single server queuing systems 2011 In: [Host publication title missing]. Conference paper (peer-reviewed)abstract Multi-step ahead response time prediction of CPU constrained computing systems is vital for admission control, overload protection and optimization of resource allocation in these systems. CPU constrained computing systems such as web servers can be modeled as single server queuing systems. These systems are stochastic and nonlinear. Thus, a well-designed nonlinear prediction scheme would be able to represent the dynamics of such a system much better than a linear scheme. A nonlinear autoregressive neural network with exogenous inputs based multi-step ahead response time predictor has been developed. The proposed estimator has many promising characteristics that make it a viable candidate for being implemented in admission control products for computing systems. It has a simple structure, is nonlinear, supports multi-step ahead prediction, and works very well under time variant and non-stationary scenarios such as single server queuing systems under time varying mean arrival rate. Performance of the proposed predictor is evaluated through simulation. Simulations show that the proposed predictor is able to predict the response times of single server queuing systems in multi-step ahead with very good precision represented by very small mean absolute and mean squared prediction errors.
16.	Amani, Payam, et al. (author) NARX-based multi-step ahead response time prediction for database servers 2011 In: [Host publication title missing]. - 2164-7143. - 9781457716768 ; , s. 813-818 Conference paper (peer-reviewed)abstract Advanced telecommunication applications are often based on a multi-tier architecture, with application servers and database servers. With a rapidly increasing development of cloud computing and data centers, characterizations of the dynamics for database servers during changing workloads will be a key factor for analysis and performance improvements in these applications. We propose a multi-step ahead response time predictor for database queries based on a nonlinear autoregressive neural network model with exogenous inputs. The estimator shows many promising characteristics which make it a viable candidate for being implemented in admission control products for database servers. Performance of the proposed predictor is evaluated through experiments on a lab setup with a MySQL-server.
17.	Andersson, Jens A, et al. (author) Analytic Model for Cross-Layer Dependencies in VDSL2 access networks 2014 In: 22nd International Conference on Software, Telecommunications and Computer Networks (SoftCOM), 2014. - 9781479964970 - 9789532900521 ; , s. 269-273 Conference paper (peer-reviewed)abstract Recent changes in user employment of Internet based services, new deployment technologies for mobile networks as well as an ongoing realisation of fixed and mobile converged networks e.g. the EU FP7 project COMBO, are significant examples of enablers for increasing demands on DSL links. Investigating cross-layer dependencies between all layers in the OSI reference model becomes increasingly important. In this paper we present an analytical model and experimental results for the relation between impulse noise on a VDSL2 link and the effect this have on the network layer packet loss. We show how the packet loss rate is dependent not only on the disturbance signal level and periodicity but also on the link utilisation.
18.	Andersson, Jens A, et al. (author) Impact of DSL link impairments on higher layer QoS parameters 2012 In: Proceedings of SNCNW 2012. ; , s. 95-98 Conference paper (peer-reviewed)abstract An increasing demand from e.g. real-time multimedia applications (IPTV, OTT) adds strains on especially DSL based access links. In this paper we argue why it is important to study DSL link impairments and their impact on QoS parameters on higher layers. We discuss the need for establishing methods for quality of service estimation with cross layer techniques and present some initial results.
19.	Andersson, Jens A, et al. (author) Physical Layer Disturbances and Network Layer Packet Loss relation in an OFDM Based System 2017 In: Proceedings of SNCNW 2017. ; , s. 25-28 Conference paper (peer-reviewed)
20.	Andersson, Jens A, et al. (author) User profiling for pre-fetching or caching in a catch-up TV network 2016 In: 2016 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB). - 9781467390446 Conference paper (peer-reviewed)abstract We investigate the potential of different pre-fetching and/or caching strategies for different user behaviour with respect to surfing or browsing in a catch-up-TV network. To this end we identify accounts and channels associated with strong or weak surfing or browsing respectively and study the distributions of hold times for the different types of behaviour. Finally we present results from a request prediction model and a caching simulation for the different types of behaviour and find that the results are relatively similar.
21.	Andersson, Jens K, et al. (author) Convergence-analysis of the internet and the telecommunication architectures 2002 In: Sixteenth Nordic Teletraffic Seminar NTS 16 : Helsinki University of Technology, Espoo August 21-23, 2002 : proceedings (Report / Helsinki University of Technology, Networking Laboratory, ISSN 1458-0322). Conference paper (other academic/artistic)abstract The convergence of the Internet and Telecommunication Architectures is a key issue in today’s telecommunication world. It is foreseen that future versions of UMTS will be all-IP based, and therefore the interest in this area is increasing. The focus in this paper is to show how to access IN-services from the Internet and other IP-based networks. Previous research of the interworking between PSTN and IP-networks will be discussed. The respective advantages of different architectures are presented and some solutions of building a bridge between the protocols used in these networks are described. Further, this paper presents some of the performance problems that may occur in such systems.
22.	Andersson, Jens K, et al. (author) Load Balancing and Admission Control of a Parlay X Application Server 2004 In: Seventeenth Nordic Teletraffic Seminar, NTS 17, Fornebu, Norway, 25-27 August 2004. - 8242305951 Conference paper (peer-reviewed)abstract To increase the number of services and applications in the telecommunication networks a new service architecture has been proposed and specified. The consortia that initiated the new service architecture is called Parlay. Since then, there has been a continued development and 3GPP the standardization group for 3G networks, is now cooperating with Parlay. 3GPP and Parlay are together specifying the Parlay/OSA standard. However, the aim with the new service architecture is to make the art of service development so easy that any software developer should be a potential application developer for telecommunication networks. It is foreseen to be a dramatic increase of new services, but it has been shown that it is still complex to create new applications. Parlay X is a standard which is an extension of Parlay/OSA, initiated to allow access to the telecommunication network capabilities via web services. The Parlay X architectures include an Application Server (AS), which translates the web service calls to Parlay/OSA commands. A typical AS is a distributed environment sensitive to overload. In this paper we propose and investigate an overload control mechanisms for an AS. The methods have been implemented in a real AS to evaluate the performance. Parlay X is a contract driven architecture, where different service providers have different constraints about minimum number of service calls served per second and maximal delays of different services. The methods and algorithms are designed to serve different service providers with different contract parameters.
23.	Andersson, Jens K, et al. (author) Performance analysis and modelling of an OSA gateway 2003 In: Personal Wireless Communications / Lecture Notes in Computer Science. - 0302-9743 .- 1611-3349. - 9783540201236 ; 2775, s. 511-517 Conference paper (peer-reviewed)abstract It is foreseen that you in the future should be able to use the same services independent of where you are positioned or which terminal that is used. The open service architectures provide these opportunities. Open Service Access (OSA) is an example of such an architecture and it is part of the specification delivered by 3GPP. This paper explains the OSA architecture and presents a model of an OSA gateway. Further, it discusses and proposes some feasible overload control mechanisms for the gateway. The behaviour of the mechanisms is investigated through simulation.
24.	Andersson, Jens K, et al. (author) Performance analysis and overload control of an open service access (OSA) architecture 2003 In: Performance and control of next-generation communication networks : [ITCom's Conference on Performance and Control of Next-Generation Communication Networks] ; 9 - 10 September 2003, Orlando, Florida, USA (SPIE proceedings series). - : SPIE. - 0819451274 ; 5244, s. 176-186 Conference paper (peer-reviewed)abstract The trend of the service architectures developed in telecommunications today is that they should be open in the sense thatthey can communicate over the borders of different networks. Instead of each network having their own service architecture with their own applications, all networks should be able to use the same applications. 3GPP, the organization developing specifications for the 3G networks has specified the standard Open Service Access (OSA), as a part of the 3G specification. OSA offers different Application Protocol Interfaces that enable an application that resides outside a network to use the capabilities of the network. This paper analyses the performance of an OSA gateway. It is examined how the overload control can be dealt with in a way to best satisfy the operators and the 3'rd parties. There are some guiding principles in the specifications, but a lot of decisions have to be made by the implementors of application servers and OSA gateways. Proposals of different requirements for an OSA architecture exist such as, minimum amount of accepted calls per second and time constraint for the maximal total delay for an application. Maximal and fair throughput have to be prioritized from the 3'rd parties view, but profit is the main interest from the operators point of view. Therefore this paperexamines a priority based proposal of an overload control mechanism taking these aspects and requirements into account.
25.	Andersson, Jens K, et al. (author) Priorities and overload control in OSA 2003 In: Fourth International Conference on 3G Mobile Communication Technologies (3G 2003) : 25 - 27 June 2003, Savoy Place, London, UK (IEE Conference Publications ; vol. 494). - : IEE. - 085296756X ; , s. 139-143 Conference paper (peer-reviewed)abstract An Open Service Access (OSA) gateway is modelled in a multi application environment. Also, an overload control mechanism is proposed. The mechanism supports different time constraints and priorities for the applications. By simulations it is shown how the proposed overload control works during different load conditions in the modelled environment.
26.	Andersson, Jens, et al. (author) Traffic shaping and dimensioning of an external overload controller in service architectures 2006 In: Proceedings. 2006 31st IEEE Conference on Local Computer Networks. - 1424404193 ; , s. 553-554 Conference paper (peer-reviewed)abstract This paper investigates the dimensioning of a server used for external overload control in service architecture. Great savings can be obtained by an operator if the dimensioning analysis is performed correctly. As one of the main parts of this paper it is shown that Poissonian arrivals is a good assumption for some services in service architectures. Methods that can be used for dimensioning are presented and examples are provided
27.	Andersson, Mikael, et al. (author) Admission control of the Apache web server 2004 In: Seventeenth Nordic Teletraffic Seminar, NTS 17, Fornebu, Norway, 25-27 August 2004. - 8242305951 Conference paper (peer-reviewed)abstract Web sites are exposed to high rates of incoming requests. The servers may become overloaded during temporary traffic peaks when more requests arrive than the server is designed for. An admission control mechanism rejects some requests whenever the arriving traffic is too high and thereby maintains an acceptable load in the system. This paper presents how admission control mechanisms can be designed with a combination of queueing theory and control theory. In this paper we model an Apache web server as a G/G/1-system and then design a PI-controller, commonly used in automatic control, for the server. The controller has been implemented as a module inside the Apache source code. Measurements from the laboratory setup show how robust the implemented controller is, and how it correspond to the results from the theoretical analysis.
28.	Andersson, Mikael, et al. (author) Admission control with service level agreements for a web server 2005 In: Proceedings of the IASTED International Conference on Internet and Multimedia Systems and Applications, EuroIMSA 2005 : February 21 - 23, 2005, Grindelwald, Switzerland. - 0889864845 Conference paper (peer-reviewed)abstract One problem with web servers is that they are sensitive to overload. The servers may become overloaded during temporary traffic peaks when more requests arrive than the server is designed for. Because overload usually occurs rather seldom, it is not economical to overprovision the servers for these traffic peaks, instead admission control mechanisms can be implemented in the servers. This pa per investigates two overload control strategies with per formance bounds for a web server. In service level agree ments, we bound average response times and throughputs for all service classes. Each request is sorted into a class, where each class is assigned a weight representing the in come for the web site owner. Then a linear optimization algorithm is applied so that the total revenue for the web site during overload is maximized.
29.	Andersson, Mikael, et al. (author) Design and evaluation of an overload control system for crisis-related Web server systems 2006 In: 2006 International Conference on Internet Surveillance and Protection. - 0769526497 Conference paper (peer-reviewed)abstract During recent years we have seen several large-scale crises. The 9/11 terror attacks, tsunamis, storms, floods and bombings have all caused a great deal of damage. A common factor in these crises has been the need for information and one important source of information is usually Web sites. In this work we investigate and design an overload control system for Web sites that are vital in crises. The overload control system uses content adaption to dynamically control Web site performance
30.	Andersson, Mikael, et al. (author) Modelling and Design of Admission Control Mechanisms for Web Servers using Non-linear Control Theory 2003 In: Performance and control of next-generation communication networks : [ITCom's Conference on Performance and Control of Next-Generation Communication Networks] ; 9 - 10 September 2003, Orlando, Florida, USA (SPIE proceedings series ; vol. 5244). - : SPIE. - 1996-756X .- 0277-786X. - 0819451274 ; 5244:1, s. 53-64 Conference paper (peer-reviewed)abstract Web sites are exposed to high rates of incoming requests. Since web sites are sensitive to overload, admission control mechanisms are often implemented. The purpose of such a mechanism is to prevent requests from entering the web server during high loads. This paper presents how admission control mechanisms can be designed and implemented with a combination of queueing theory and control theory. Since web servers behave non-linear and stochastic, queueing theory can be used for web server modelling. However, there are no mathematical tools in queueing theory to use when designing admission control mechanisms. Instead, control theory contains the needed mathematical tools. By analysing queueing systems with control theoretic methods, good admission control mechanisms can be designed for web server systems. In this paper we model an Apache web server as a GI/G/1-system. Then, we use control theory to design a PI-controller, commonly used in automatic control, for the web server. In the paper we describe the design of the controller and also how itcan be implemented in a real system. The controller has been implemented and tested together with the Apache web server. The server was placed in a laboratory network together with a traffic generator which was used to represent client requests. Measurements in the laboratory setup show how robust the implemented controller is, and how it correspond to the results from the theoretical analysis.
31.	Andersson, Mikael, et al. (author) Performance modeling of an Apache web server with bursty arrival traffic 2003 In: IC'03 : proceedings of the international conference on internet computing. - 1932415025 ; , s. 508-511 Conference paper (peer-reviewed)abstract Performance modeling is an important topic in capacity planning and overload control for web servers. We present a queueing model of an Apache web server that uses bursty arrival traffic. The arrivals of HTTP requests is assumed to be a Markov Modulated Poisson Process and the service discipline of the server is processor sharing. The total number of requests that can be processed at one time is limited to K. We obtain web server performance metrics such as average response time, throughput and blocking probability by simulations. Compared to other models, our model is conceptually simple. The model has been validated through measurements and simulations in our lab. The performance metrics predicted by the model fit well to the experimental outcome.
32.	Arvidsson, Åke, 1957-, et al. (author) Analysis of user demand patterns and locality for YouTube traffic 2013 In: 25th International Teletraffic Congress. - : IEEE Communications Society. - 9781479907991 Conference paper (peer-reviewed)abstract Video content, of which YouTube is a major part, constitutes a large share of residential Internet traffic. In this paper, we analyse the user demand patterns for YouTube in two metropolitan access networks with more than 1 million requestsover three consecutive weeks in the first network and more than 600,000 requests over four consecutive weeks in the second network.In particular we examine the existence of “local interest communities”, i.e. the extent to which users living closer to each other tend to request the same content to a higher degree, and it is found that this applies to (i) the two networks themselves; (ii) regions within these networks (iii) households with regions and (iv) terminals within households. We also find that different types of access devices (PCs and handhelds) tend to form similar interest communities.It is also found that repeats are (i) “self-generating” in the sense that the more times a clip has been played, the higher the probability of playing it again, (ii) “long-lasting” in the sense that repeats can occur even after several days and (iii) “semi regular”in the sense that replays have a noticeable tendency tooccur with relatively constant intervals.The implications of these findings are that the benefits from large groups of users in terms of caching gain may be exaggerated, since users are different depending on where they live and what equipment they use, and that high gains can be achieved in relatively small groups or even for individual users thanks totheir relatively predictable behaviour.
33.	Arvidsson, Åke, et al. (author) Analysis of user demand patterns and locality for YouTube traffic 2013 In: In the Proceedings of the 25th International Teletraffic Congress (ITC). Conference paper (peer-reviewed)abstract Video content, of which YouTube is a major part, constitutes a large share of residential Internet traffic. In this paper, we analyse the user demand patterns for YouTube in two metropolitan access networks with more than 1 million requests over three consecutive weeks in the first network and more than 600,000 requests over four consecutive weeks in the second network. In particular we examine the existence of "local interest communities", i.e. the extent to which users living closer to each other tend to request the same content to a higher degree, and it is found that this applies to (i) the two networks themselves; (ii) regions within these networks (iii) households with regions and (iv) terminals within households. We also find that different types of access devices (PCs and handhelds) tend to form similar interest communities. It is also found that repeats are (i) "self-generating" in the sense that the more times a clip has been played, the higher the probability of playing it again, (ii) "long-lasting" in the sense that repeats can occur even after several days and (iii) "semiregular" in the sense that replays have a noticeable tendency to occur with relatively constant intervals. The implications of these findings are that the benefits from large groups of users in terms of caching gain may be exaggerated, since users are different depending on where they live and what equipment they use, and that high gains can be achieved in relatively small groups or even for individual users thanks to their relatively predictable behaviour.
34.	Aurelius, Andreas, et al. (author) How much of the bandwidth do we actually use? : An investigation of residential access traffic load 2012 In: International Conference on Transparent Optical Networks. - : IEEE. - 9781467322270 Conference paper (peer-reviewed)abstract Internet traffic from a fibre based residential access network is investigated concerning traffic volumes and link load. Also the cost of the services is analyzed. We show that 1 Mbps accesses subscribers maintain high loads, and that the price they pay per GB used is five times higher than the one paid by 100 Mbps access subscribers.
35.	Aurelius, Andreas, et al. (author) Leveraging network and traffic measurements for content distribution and interpersonal communication services with sufficient quality 2011 Conference paper (peer-reviewed)abstract In this paper, we discuss research problems for enabling content distribution and supporting real-time interpersonal communication services (e.g. voice and video) over best effort networks with sufficient quality. We take a practical view of content distribution and quality, and this is the reason for the term “sufficient”. We argue that the understanding of quality as perceived by the user is a key factor in this context, but also that the understanding of context dependence is a key factor for delivering services which are “good enough” to make the user satisfied. We base our assumptions upon results from the Celtic TRAMMS project, and we describe how to leverage upon the framework for traffic measurements that was built up in that project. Moreover, we identify key technological components that are common for optimization of content delivery and real-time interpersonal communication services such as VoIP and videoconferencing. We also describe how the research problems stated will be tackled in the newly started IPNQSIS project.
36.	Aurelius, Andreas, et al. (author) Streaming media over the Internet: Flow based analysis in live access networks 2011 In: [Host publication title missing]. Conference paper (peer-reviewed)abstract Multimedia service delivery over the Internet is a success. The number of services available and the number of people accessing them is huge. In this paper, we investigate multimedia streaming services over the Internet. Our analysis is based on traffic measurement in live access fiber-to-the-home networks. We study parameters like traffic volume and flow characteristics for selected services. Especially the Swedish P2P video service Voddler and the Swedish P2P music service Spotify are studied. We show that indeed these services are widely used (20% of local hosts using Voddler, 65 % of local hosts using Spotify). We also show that they are different concerning the flow characteristics, with many short flows for Voddler and longer flows for Spotify. One thing that they have in common in our measurements is that the outbound, or uplink, traffic volume is larger than the inbound.
37.	Aurelius, Andreas, et al. (author) Traffic analysis in the TRAMMS project 2009 Conference paper (peer-reviewed)abstract Internet usage is evolving, from the traditional WWW usage (i.e. downloading web pages), to triple-play usage where households may have all their communication services (telephony, data, TV) through their broadband access connection. The challenge is to design IP access networks so that they can deliver services with strict QoS demands such as IPTV at the same time as having capacity for (from the operator's perspective) unwanted traffic, for example file sharing, demanded by the users. One important part in meeting this research challenge is to identify and monitor Internet usage. Traffic modeling is tightly coupled both to traffic measurements and to engineering and techno economics. Independent of the type of model, traffic measurements are a common denominator that provide input for the model parameters. In this paper, detailed traffic measurements performed as a part of the Celtic TRAMMS project are presented.
38.	Aurelius, Andreas, et al. (author) TRAMMS: Monitoring the evolution of residential broadband Internet traffic 2010 In: [Host publication title missing]. Conference paper (peer-reviewed)abstract Traffic measurements in broadband access networks are crucial from several points of view. A better understanding of traffic patterns can lead to more efficient network design, which leads to energy and cost savings for the operator and improved end user services. This paper reports on selected traffic measurement results from the Celtic TRAMMS project. The measurements were performed in broadband access networks in Sweden and Spain. The vast majority of the traffic volume is video based and from peer-to-peer applications. This suggests that future access networks should be symmetrical in order to properly cope with the traffic patterns of the future. Geographic locality of end-to-end flows has been identified for incoming and outgoing traffic in Spain, which may be used to analyze peering between ISP’s. Finally, we show that stricter legislation in Sweden targeting illegal file sharing led to a dramatic decrease of the traffic. This means that factors not controlled by the networking community may seriously impact traffic patterns and user behaviour thereby indicating the need for closer collaboration between researchers and network designers on one side and politicians and regulators on the other side.
39.	Becker, Per, et al. (author) Kvinnor, män och matematik 2010 In: Lärande i LTH. ; :9, s. 3-3 Journal article (pop. science, debate, etc.)
40.	Belgacem, Ali, et al. (author) Intelligent multi-agent reinforcement learning model for resources allocation in cloud computing 2022 In: Journal of King Saud University - Computer and Information Sciences. - : Elsevier BV. - 1319-1578. ; 34:6, s. 2391-2404 Journal article (peer-reviewed)abstract Now more than ever, optimizing resource allocation in cloud computing is becoming more critical due to the growth of cloud computing consumers and meeting the computing demands of modern technology. Cloud infrastructures typically consist of heterogeneous servers, hosting multiple virtual machines with potentially different specifications, and volatile resource usage. This makes the resource allocation face many issues such as energy conservation, fault tolerance, workload balancing, etc. Finding a comprehensive solution that considers all these issues is one of the essential concerns of cloud service providers. This paper presents a new resource allocation model based on an intelligent multi-agent system and reinforcement learning method (IMARM). It combines the multi-agent characteristics and the Q-learning process to improve the performance of cloud resource allocation. IMARM uses the properties of multi-agent systems to dynamically allocate and release resources, thus responding well to changing consumer demands. Meanwhile, the reinforcement learning policy makes virtual machines move to the best state according to the current state environment. Also, we study the impact of IMARM on execution time. The experimental results showed that our proposed solution performs better than other comparable algorithms regarding energy consumption and fault tolerance, with reasonable load balancing and respectful execution time.
41.	Biswas, Sinchan, et al. (author) Implementation of Sequential Detection of Replay Attacks for a Cloud Native Controller 2023 In: The 31st International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2023). - 9798350301076 Conference paper (peer-reviewed)abstract This paper focuses on the investigation of a sequential detection policy for combating the effect of the replay attack on a cloud-native controller. In reply attacks, an external attacker records true signals for some time duration and replays them later. The effect of such an attack is mitigated by adding random signals to the optimal control signal before the actuation process, which is known as the watermarking policy. We study the effectiveness of this joint scheme of sequential detection with watermarking in a cloud-native controller with varying levels of delay introduced in the communication network between the cloud server and the physical plant. Our study shows that the scheme performs well for the cloud-native controller and that the scheme is able to mitigate the effect of the replay attack when the control signals arrive in a timely fashion, i.e., without significant delay from the controller to the physical plant.
42.	Brunnström, Kjell, et al. (author) 2D no-reference video quality model development and 3D video transmission quality 2012 In: Proceedings of the Sixth International Workshop on Video Processing and Quality Metrics for Consumer Electronics VPQM-2012. Conference paper (other academic/artistic)abstract This presentation will target two different topics in video quality assessment. First, we discuss 2D no-reference video quality model development. Further, we discuss how to find suitable quality for 3D video transmission. No-reference metrics are the only practical option for monitoring of 2D video quality in live networks. In order to decrease the development time, it might be possible to use full-reference metrics for this purpose. In this work, we have evaluated six full-reference objective metrics in three different databases. We show statistically that VQM performs the best. Further, we use these results to develop a lightweight no-reference model. We have also investigated users' experience of stereoscopic 3D video quality by performing the rating of two subjective assessment datasets, targeting in one dataset efficient transmission in the transmission error free case and error concealment in the other. Among other results, it was shown that, based on the same level of quality of experience, spatial down-sampling may lead to better bitrate efficiency while temporal down-sampling will be worse. When network impairments occur, traditional error 2D concealment methods need to be reinvestigated as they were outperformed switching to 2D presentation.
43.	Brunnström, Kjell, 1960-, et al. (author) Future Media Distribution : An Innovation Agenda for Digital Media Distribution 2015 Reports (pop. science, debate, etc.)abstract The purpose of this agenda is to create a solid research and innovation program concerning digital media distribution. It aims at groundbreaking renewal and a sustainable development for both Swedish industry and Swedish society. The agenda starts out by mapping the state of affairs in the Trends-chapter, then points out difficulties in Challenges, provides Goals, and lists the means to achieve these goals in the Activities-chapter.
44.	Bür, Kaan, et al. (author) Evaluation of selective broadcast algorithms for safety applications in vehicular ad hoc networks 2011 In: International Journal of Vehicular Technology. - : Hindawi Limited. - 1687-5702 .- 1687-5710. ; 2011 Journal article (peer-reviewed)abstract Just as the wireless communication technology develops further to achieve higher performance, new application areas emerge to challenge its limits. Vehicular ad hoc networks are one of these areas; and emergency situation warning is one of their most popular potential applications since traffic safety is a real concern for everyone. Due to the life-critical nature of emergency applications, however, it is extremely important to ensure the solutions proposed meet the high standards required, such as reliable, timely, and guaranteed delivery of the safety warning in a situation like car collision avoidance. In order to put the candidate solutions to the test and to evaluate their feasibility, we adopt the approach of computer simulation. We implement four different selective broadcast algorithms used for information dissemination in vehicular ad hoc networks, and compare their performance under identical and realistic simulation conditions. Our goal is to provide our reader with an evaluation focussing on the performance with respect to safety, rather than to classical network aspects like throughput, loss, and delay. Therefore, we define four new performance criteria to address the effectiveness, efficiency, timeliness, and overhead of the candidate broadcast algorithms in terms of safety warning delivery. The results we obtain using these criteria help us to understand better the design requirements of a high-performance selective broadcast algorithm.
45.	Bür, Kaan, et al. (author) Power adaptive selective broadcast in vehicular ad hoc networks for improved traffic safety 2011 Conference paper (peer-reviewed)
46.	Bür, Kaan, et al. (author) Selective broadcast for VANET safety applications 2011 Conference paper (peer-reviewed)
47.	Cao, Jianhua, et al. (author) Web Server Performance Modeling using an M/G/1/KPS Queue 2003 In:* ICT'2003 : 10th international conference on telecommunications. Volume 2. - 0780376617 ; , s. 1501-1506 Conference paper (peer-reviewed)abstract Performance modeling is an important topic in capacity planning and overload control for web servers. We present an M/G/1/K*PS queueing model of a web server. The arrival process of HTTP requests is assumed to be Poissonian and the service discipline is processor sharing. The total number of requests that can be processed at one time is limited to K. We obtain closed form expressions for web server performance metrics such as average response time, throughput and blocking probability. The average of the service time requirement and the limit of the number of requests being served are model parameters. The parameters are estimated by maximizing the log-likelihood function of the measured average response time. Compared to other models, our model is conceptually simple and it is easy to estimate model parameters. The model has been validated through measurements in our lab. The performance metrics predicted by the model fit well to the experimental outcome.
48.	Chamideh, Seyedezahra, et al. (author) A Safe and Robust Autonomous Intersection Management System Using a Hierarchical Control Strategy and V2I Communication 2023 In: IEEE Systems Journal. - 1937-9234. ; 17:1 Journal article (peer-reviewed)abstract Connected autonomous vehicles can significantly improve the safety and mobility of urban transportation systems. However, these systems are vulnerable to model uncertainties, wireless communication impairments, and external disturbances. In this article, we propose a new autonomous intersection management (AIM) system, called hierarchical model predictive control (HMPC). In HMPC, the intersection coordination unit (ICU) in a global centralized layer is responsible for assigning a safe speed to each vehicle while minimizing the system's cost. In the Local decentralized layer, each vehicle is responsible for tracking the reference speed assigned by the ICU, while avoiding collisions. In our method, each vehicle can use its own sensors to monitor its close surroundings, and take its own decisions on its movements, independent on the control decisions sent from the ICU. We investigate the safety, scalability and robustness of HMPC compared with two well-known AIM methods based on centralized and decentralized control strategies. For the evaluation, we use simulation of urban mobility (SUMO). Further, we study the scalability and performance of the algorithms in the presence of communication impairments associated with wireless channels. Our simulation results show that HMPC can safely handle high traffic flow rates. Also, HMPC is robust to uncertainties caused by the wireless communication.
49.	Chamideh, Seyedezahra, et al. (author) Centralized Coordination of Autonomous Vehicles at Intersections 2020 In: 2020 International Conference on Software, Telecommunications and Computer Networks (SoftCOM). - 9789532900996 - 9781728175386 Conference paper (peer-reviewed)abstract Recent advances in autonomous vehicles present new opportunities in Intelligent transportation systems (ITS) to address urban transport challenges. Therefore, urban traffic scenarios, and in particular intersections as a bottleneck of transportation network, has received significant attention. In this paper we investigate intelligent traffic control mechanisms for autonomous vehicles at intersections as a replacement of traditional intersection control. An edge cloud controller is used to deliver services that provide traffic safety and efficiency to vehicles. Two well-cited optimization algorithms for cooperative vehicles are compared with realistic simulations in SUMO. This side by side comparison helps to gain insight into the strengths and limitations of these types of algorithms.
50.	Chamideh, Seyedezahra, et al. (author) Enhancing Traffic Flow and Safety in Mixed Vehicle Fleets: Mitigating the Influence of Non-Cooperative Vehicles on Autonomous Intersection Management Systems 2023 In: 2023 International Conference on Software, Telecommunications and Computer Networks (SoftCOM). - 9798350301076 Conference paper (peer-reviewed)abstract With the rapid advancement of autonomous vehicle technology, integrating mixed autonomous and non-autonomous vehicles that are not cooperative in vehicular network has become a significant challenge. This paper presents an innovative Autonomous Intersection Management (AIM) system designed to optimize traffic flow and enhance intersection safety in such mixed traffic scenarios. By utilizing vehicle-to-infrastructure (V2I) communication and advanced intersection control algorithms, the AIM system showcases the potential of next-generation vehicular network technologies in revolutionizing intersection management. To evaluate the performance of the AIM system and the impact of non-cooperative vehicles, extensive simulations were conducted using realistic traffic scenarios and a mixed traffic model. The results demonstrate that the proposed system effectively enhances intersection throughput, and ensures safe and efficient operations, particularly in situations involving a high proportion of autonomous vehicles. Additionally, the system’s robustness is demonstrated by evaluating its performance under various traffic flow rates and considering imperfect wireless communication conditions.

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