Henrik Abrahamsson

Swedish Institute of Computer Science, Киста, Stockholm, Sweden

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Publications (22)1.94 Total impact

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    ABSTRACT: The increased capacity needs, primarily driven by content distribution, and the vision of Internet-of-Things with billions of connected devices pose radically new demands on future wireless and mobile systems. In general the increased diversity and scale result in complex resource management and optimization problems in both radio access networks and the wired core network infrastructure. We summarize results in this area from a collaborative Sino-Swedish project within IMT Advanced and Beyond, covering adaptive radio resource management, energy-aware routing, OpenFlow-based network virtualization, data center networking, and access network caching for TV on demand.
    Sciece China. Information Sciences 02/2013; 56(2). · 0.71 Impact Factor
  • H. Abrahamsson, M. Bjorkman
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    ABSTRACT: Today video and TV distribution dominate Internet traffic and the increasing demand for high-bandwidth multimedia services puts pressure on Internet service providers. In this paper we simulate TV distribution with time-shift and investigate the effect of introducing a local cache close to the viewers. We study what impact TV program popularity, program set size, cache replacement policy and other factors have on the caching efficiency. The simulation results show that introducing a local cache close to the viewers significantly reduces the network load from TV-on-Demand services. By caching 4% of the program volume we can decrease the peak load during prime time by almost 50%. We also show that the TV program type and how program popularity changes over time can have a big influence on cache hit ratios and the resulting link loads.
    Computing, Networking and Communications (ICNC), 2013 International Conference on; 01/2013
  • Henrik Abrahamsson, Mattias Nordmark
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    ABSTRACT: Today increasingly large volumes of TV and video are distributed over IP-networks and over the Internet. It is therefore essential for traffic and cache management to understand TV program popularity and access patterns in real networks. In this paper we study access patterns in a large TV-on-Demand system over four months. We study user behaviour and program popularity and its impact on caching. The demand varies a lot in daily and weekly cycles. There are large peaks in demand, especially on Friday and Saturday evenings, that need to be handled. We see that the cacheability, the share of requests that are not first-time requests, is very high. Furthermore, there is a small set of programs that account for a large fraction of the requests. We also find that the share of requests for the top most popular programs grows during prime time, and the change rate among them decreases. This is important for caching. The cache hit ratio increases during prime time when the demand is the highest, and aching makes the biggest difference when it matters most. We also study the popularity (in terms of number of requests and rank) of individual programs and how that changes over time. Also, we see that the type of programs offered determines what the access pattern will look like.
    Proceedings of the 2012 ACM conference on Internet measurement conference; 11/2012
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    H. Abrahamsson, M. Björkman
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    ABSTRACT: IPTV, where television is distributed over the Internet Protocol in a single operator network, has become popular and widespread. Many telecom and broadband companies have become TV providers and distribute TV channels using multicast over their backbone networks. IPTV also means an evolution to time-shifted television where viewers now often can choose to watch the programs at any time. However, distributing individual TV streams to each viewer requires a lot of bandwidth and is a big challenge for TV operators. In this paper we present an empirical IPTV workload model, simulate IPTV distribution with time-shift, and show that local caching can limit the bandwidth requirements significantly.
    Performance Evaluation of Computer and Telecommunication Systems (SPECTS), 2010 International Symposium on; 08/2010
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    ABSTRACT: The Internet Protocol (IP) has been proven very flexible, being able to accommodate all kinds of link technologies and supporting a broad range of applications. The basic principles of the original Internet architecture include end-to-end addressing, global routeability and a single namespace of IP addresses that unintentionally serves both as locators and host identifiers. The commercial success and widespread use of the Internet have lead to new requirements, which include Internetworking over business boundaries, mobility and multi-homing in an untrusted environment. Our approach to satisfy these new requirements is to introduce a new Internetworking layer, the node identity layer. Such a layer runs on top of the different versions of IP, but could also run directly on top of other kinds of network technologies, such as MPLS and 2G/3G PDP contexts. This approach enables connectivity across different communication technologies, supports mobility, multi-homing, and security from ground up. This paper describes the Node Identity Architecture in detail and discusses the experiences from implementing and running a prototype.
    Computer Networks 01/2010; · 1.23 Impact Factor
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    H. Abrahamsson, M. Bjorkman
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    ABSTRACT: Internet traffic volumes continue to grow at a great rate, now pushed by video and TV distribution in the networks. This brings up the need for traffic engineering mechanisms to better control the traffic. The objective of traffic engineering is to avoid congestion in the network and make good use of available resources by controlling and optimising the routing function. The challenge for traffic engineering in IP networks is to cope with the dynamics of Internet traffic demands. Today, the main alternative for intra-domain traffic engineering in IP networks is to use different methods for setting the weights in the routing protocols OSPF and IS-IS. In this paper we revisit the weight setting approach to traffic engineering but with focus on robustness. We propose l-balanced weight settings that route the traffic on the shortest paths possible but make sure that no link is utilised to more than a given level l. This gives efficient routing of traffic and controlled spare capacity to handle unpredictable changes in traffic. We present a heuristic search method for finding l-balanced weight settings and show that it works well in real network scenarios.
    Broadband Communications, Networks, and Systems, 2009. BROADNETS 2009. Sixth International Conference on; 10/2009
  • Henrik Abrahamsson, Per Kreuger
    ERCIM News. 01/2009; 2009.
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    Per Kreuger, Henrik Abrahamsson
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    ABSTRACT: Recently many new IPTV providers have appeared, typically telephone and broadband companies, that now distribute scheduled TV channels, sometimes high-definition TV and video-on-demand (VoD) over IP in their own network. From a network management perspective, distribution of IPTV can be seen as a scheduling problem with the network links and storage facilities as resources and the objective to balance the overall load in the network. We show that scheduling and optimisation techniques can be used to make the distribution of IPTV more efficient by pushing content out to caches in the network to the right place at the right time.
    IP Operations and Management, 9th IEEE International Workshop, IPOM 2009, Venice, Italy, October 29-30, 2009. Proceedings; 01/2009
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    ABSTRACT: We present the TOTEM open source Traffic Engineering (TE) toolbox and a set of TE methods that we have designed and/or integrated. These methods cover intra-domain and inter-domain TE, IP-based and MPLS-based TE. They are suitable for network optimisation, better routing of traffic for providing QoS, load balancing, protection and restoration in case of failure, etc. The toolbox is designed to be deployed as an on-line tool in an operational network, or used off-line as an optimisation tool or as a traffic engineering simulator.
    Computer Communications. 01/2006; 29:593-610.
  • Anders Gunnar, Henrik Abrahamsson, Mattias Söderqvist
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    ABSTRACT: Today, the main alternative for intra-domain traffic engineering in IP networks is to use different methods for setting the weights (and so decide upon the shortest-paths) in the routing protocols OSPF and IS-IS. In this paper we study how traffic engineering perform in real networks. We analyse different weight-setting methods and compare performance with the optimal solution given by a multi-commodity flow optimization problem. Further, we investigate their robustness in terms of how well they manage to cope with estimated traffic matrix data. For the evaluation we have access to network topology and traffic data from an operational IP network.
    09/2005: pages 202-211;
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    ABSTRACT: Ambient Networks (AN) are under development and they are based on novel networking concepts and systems that will enable a wide range of user and business communication scenarios beyond today's fixed, rd generation mobile and IP standards. Central to this project is the concept of Ambient Control Space (ACS) and the Domain Manager control function, which manages the underlying data transfer capabilities and presents a set of interfaces towards the supported services and applications. Network Management Systems of Ambient Networks must work in an environment where heterogeneous networks compose and cooperate, on demand and transparently, without the need for manual (pre or re) -configuration or offline negotiations between network operators. To achieve these goals, ambient network management systems must become dynamic, distributed, self-managing and responsive to the network and its ambience. This paper describes the different management research challenges and four solution approaches (i.e. Pattern-based Management, Peer-to-Peer Management, (Un)PnP Management, Traffic Engineering Management Application Approaches) that enable efficient management of ambient networks, and the relationships between them, and presents the main results achieved so far.
    Mobility Aware Technologies and Applications, Second International Workshop, MATA 2005, Montreal, Canada, October 17-19, 2005, Proceedings; 01/2005
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    Henrik Abrahamsson, Bengt Ahlgren
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    ABSTRACT: Several studies of Internet traffic have shown that it is a small percentage of the flows that dominate the traffic. This is often referred to as the mice and elephants phenomenon. It has been proposed that this might be one of very few invariants of Internet traffic and that this property could somehow be used for traffic engineering purposes. The idea being that one in a scalable way could control a major part of the traffic by only keeping track of a small number of flows. But for this the large flows must also be stable in the meaning that they should be among the largest flows during long periods of time. In this work we analyse packet traces of Internet traffic and study the temporal characteristics of large aggregated traffic flows defined by destination address prefixes.
    06/2004;
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    ABSTRACT: System management addresses the provision of functions required for controlling, planning, allocating, monitoring, and deploying the resources of a network and of its services in order to optimize its efficiency and productivity and to safeguard its operation. It is also an enabler for the creation and sustenance of new business models and value chains, reflecting the different roles the service providers and users of a network can assume. Ambient Network represents a new networking approach and it aims to enable the cooperation of heterogeneous networks, on demand and transparently, to the potential users, without the need for pre-configuration or offline negotiation between network operators. To achieve these goals, ambient network management systems have to become dynamic, adaptive, autonomic and responsive to the network and its ambience. This paper discusses relationships between the concepts of autonomous and self-manageability and those of ambient networking, and the challenges and benefits that arise from their employment.
    Mobility Aware Technologies and Applications, First International Workshop,MATA 2004, Florianópolis, Brazil, October 20-22, 2004, Proceedings; 01/2004
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    ABSTRACT: We prove a result concerning objective functions that can be used to obtain efficient and balanced solutions to the multi-commodity network flow problem. This type of solution is of interest when routing traffic in the Internet. A particular case of the result proved here (see Corollary 2 below) was stated without proof in a previous paper.
    06/2002;
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    Henrik Abrahamsson, Ian Marsh
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    ABSTRACT: Dynamic Transfer Mode (DTM) is a ring based MAN technology that provides a channel abstraction with a dynamically adjustable capacity. TCP is a reliable end to end transport protocol capable of adjusting its rate. The primary goal of this work is investigate the coupling of dynamically allocating bandwidth to TCP flows with the a#ect this has on the congestion control mechanism of TCP. In particular we wanted to find scenerios where this scheme does not work, where either all the link capacity is allocated to TCP or congestion collapse occurs and no capacity is allocated to TCP. We have created a simulation environment using ns-2 to investigate TCP over networks which have a variable capacity link. We begin with a single TCP Tahoe flow over a fixed bandwidth link and progressively add more complexity to understand the behaviour of dynamically adjusting link capacity to TCP and vice versa. 1
    01/2002;
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    ABSTRACT: Intra-domain routing in the Internet normally uses a single shortest path to forward packets towards a specific destination with no knowledge of trac demand. We present an intra-domain routing algo- rithm based on multi-commodity flow optimisation which enable load sensitive forwarding over multiple paths. It is neither constrained by weight-tuning of legacy routing protocols, such as OSPF, nor requires a totally new forwarding mechanism, such as MPLS. These character- istics are accomplished by aggregating the trac flows destined for the same egress into one commodity in the optimisation and using a hash based forwarding mechanism. The aggregation also results in a reduc- tion of computational complexity which makes the algorithm feasible for on-line load balancing. Another contribution is the optimisation objec- tive function which allows precise tuning of the tradeo between load balancing and total network eciency.
    From QoS Provisioning to QoS Charging, Third COST 263 International Workshop on Quality of Future Internet Services, QofIS 2002, and Second International Workshop on Internet Charging and QoS Technologies, ICQT 2002, Zurich, Switzerland, October 16-18, 2002, Proceedings; 01/2002
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    Henrik Abrahamsson, Olof Hagsand, Ian Marsh
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    ABSTRACT: New optical network technologies provide opportunities for fast, controllable bandwidth management. These technologies can now explicitly provide resources to data paths, creating demand driven bandwidth reservation across networks where an applications bandwidth needs can be meet almost exactly. Dynamic synchronous Transfer Mode (DTM) is a gigabit network technology that provides channels with dynamically adjustable capacity. TCP is a reliable end-to-end transport protocol that adapts its rate to the available capacity. Both TCP and the DTM bandwidth can react to changes in the network load, creating a complex system with inter-dependent feedback mechanisms. The contribution of this work is an assessment of a bandwidth allocation scheme for TCP flows on variable capacity technologies. We have created a simulation environment using ns-2 and our results indicate that the allocation of bandwidth maximises TCP throughput for most flows, thus saving valuable capacity when compared to a scheme such as link over-provisioning. We highlight one situation where the allocation scheme might have some deficiencies against the static reservation of resources, and describe its causes. This type of situation warrants further investigation to understand how the algorithm can be modified to achieve performance similar to that of the fixed bandwidth case.
    12/2001: pages 117-129;
  • Henrik Abrahamsson, Bengt Ahlgren
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    ABSTRACT: We model a web client using empirical probability distributions for user clicks and transferred data sizes. By using a heuristic threshold value to distinguish user clicks in a packet trace we get a simple method for analyzing large packet traces in order to get information about user OFF times and amount of data transferred due to a user click. We derive the empirical probability distributions from the analysis of the packet trace. The heuristic is not perfect, but we believe it is good enough to produce a useful web client model. We use the empirical model to implement a web client traffic generator. The characteristics of the generated traffic is very close to the original packet trace, including selfsimilar properties.
    10/2000;
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    Henrik Abrahamsson
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    ABSTRACT: Measurement and analysis of real traffic is important to gain knowledge about the char-acteristics of the traffic. Without measurement, it is impossible to build realistic traffic models. It is recent that data traffic was found to have self-similar properties. In this thesis work traffic captured on the network at SICS and on the Supernet, is shown to have this fractal-like behaviour. The traffic is also examined with respect to which pro-tocols and packet sizes are present and in what proportions. In the SICS trace most packets are small, TCP is shown to be the predominant transport protocol and NNTP the most common application. In contrast to this, large UDP packets sent between not well-known ports dominates the Supernet traffic. Finally, characteristics of the client side of the WWW traffic are examined more closely. In order to extract useful informa-tion from the packet trace, web browsers use of TCP and HTTP is investigated includ-ing new features in HTTP/1.1 such as persistent connections and pipelining. Empirical probability distributions are derived describing session lengths, time between user clicks and the amount of data transferred due to a single user click. These probability distributions make up a simple model of WWW-sessions.
    10/1999;
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    Henrik Abrahamsson, Anders Gunnar
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    ABSTRACT: The focus of this paper is on traffic engineering in ambi-ent networks. We describe and categorize different alter-natives for making the routing more adaptive to the cur-rent traffic situation and discuss the challenges that ambi-ent networks pose on traffic engineering methods. One of the main objectives of traffic engineering is to avoid con-gestion by controlling and optimising the routing function, or in short, to put the traffic where the capacity is. The main challenge for traffic engineering in ambient networks is to cope with the dynamics of both topology and traffic demands. Mechanisms are needed that can handle traffic load dynamics in scenarios with sudden changes in traffic demand and dynamically distribute traffic to benefit from available resources. Trade-offs between optimality, stabil-ity and signaling overhead that are important for traffic en-gineering methods in the fixed Internet becomes even more critical in a dynamic ambient environment.