Internet connectivity takes a strategic importance for a growing number of companies. Therefore, for reliability and performance reasons, many Internet service providers and corporate networks connect to at least two providers, a practice called multihoming. However, the current multihoming mechanism contributes to the explosive growth of the Internet routing tables. This growth has major implications for routers on storage requirements, protocol overhead and stability, and forwarding performance. As a consequence, the traditional way to be multihomed in IPv4 is prevented in the next generation IPv6 Internet. Many approaches for IPv6 multihoming were proposed, with little consideration for traffic engineering aspects. The aim of the thesis is to bridge this gap. The thesis investigates the way to best provide traffic engineering for IPv6 multihomed sites. It first demonstrates that Host-Centric multihoming, the foreseen approach for IPv6 multihoming, is the most promising in terms of fault-tolerance and traffic engineering capabilities. Compared to traditional multihoming approaches, our simulation results show that Host-Centric IPv6 multihomed sites are able to obtain lower delays by leveraging the path diversity that underlies the Internet. Unfortunately, no traffic engineering mechanism is available for this multihoming approach. Therefore, this thesis next presents a technique to effectively use the multiple interdomain paths that exist between multihomed sites. The proposed mechanism allows the multihomed sites to control how their flows are distributed over the links with their providers. The mechanism is able to take into account complex and very dynamic routing policies. Finally, the thesis proposes the use of synthetic coordinates as a scalable and efficient way to help hosts in selecting the interdomain paths with the lowest delays. Experimental results with real measurements show that this mechanism allows sites to avoid all paths with really bad delays, and to most often select the lowest delay path.

Next Generation networks (3G and beyond) are evolving towards all IP based systems with the aim to provide global coverage. For Mobility in IP based networks, Mobile IPv6 is considered as a standard by both industry and research community, but this mobility protocol has some reliability issues. There are a number of elements that can interrupt the communication between Mobile Node (MN) and Corresponding Node (CN), however the scope of this research is limited to the following issues only: • Reliability of Mobility Protocol • Home Agent Management • Handovers • Path failures between MN and CN First entity that can disrupt Mobile IPv6 based communication is the Mobility Anchor point itself, i.e. Home Agent. Reliability of Home Agent is addressed first because if this mobility agent is not reliable there would be no reliability of mobile communication. Next scenario where mobile communication can get disrupted is created by MN itself and it is due to its mobility. When a MN moves around, at some point it will be out of range of its active base station and at the same time it may enter the coverage area of another base station. In such a situation, the MN should perform a handover, which is a very slow process. This handover delay is reduced by introducing a “make before break” style handover in IP network. Another situation in which the Mobile IPv6 based communication can fail is when there is a path failure between MN and CN. This situation can be addressed by utilizing multiple interfaces of MN at the same time. One such protocol which can utilize multiple interfaces is SHIM6 but it was not designed to work on mobile node. It was designed for core networks but after some modification in the protocol , it can be deployed on mobile nodes. In this thesis, these issues related to reliability of IPv6 based mobile communication have been addressed.

<p>The emergence of real-time applications, like Voice over IP and video conferencing, in IP networks implies a challenge to the underlying infrastructure. Several real-time applications have requirements on timeliness as well as on reliability and are accompanied by signaling applications to set up, tear down and control the media sessions. Since neither of the traditional transport protocols responsible for end-to-end transfer of messages was found suitable for signaling traffic, the Stream Control Transmission Protocol (SCTP) was standardized. The focus for the protocol was initially on telephony signaling applications, but it was later widened to serve as a general purpose transport protocol. One major new feature to enhance robustness in SCTP is multihoming, which enables for more than one path within the same association.</p><p>In this thesis we evaluate some of the mechanisms affecting transmission performance in case of a switchover between paths in a multihomed SCTP session. The major part of the evaluation concerns a failure situation, where the current path is broken. In case of failure, the endpoint does not get an explicit notification, but has to react upon missing acknowledgements. The challenge is to distinguish path failure from temporary congestion to decide  when to switch to an alternate path. A too fast switchover may be spurious, which could reduce transmission performance, while a too late switchover also results in reduced transmission performance. This implies a tradeoff which involves several protocol as well as network parameters and we elaborate among these to give a coherent view of the parameters and their interaction. Further, we present a recommendation on how to tune the parameters to meet  telephony signaling requirements, still without violating fairness to other traffic.</p><p>We also consider another angle of switchover performance, the startup on the alternate path. Since the available capacity is usually unknown to the sender, the transmission on a new path is started at a low rate and then increased as acknowledgements of successful transmissions return. In case of switchover in the middle of a media session the startup phase after a switchover could cause problems to the application. In multihomed SCTP the availability of the alternate path makes it feasible for the end-host to estimate the available capacity on the alternate path prior to the switchover. Thus, it would be possible to implement a more efficient startup scheme. In this thesis we combine different switchover scenarios with relevant traffic. For these combinations, we analytically evaluate and quantify the potential performance gain from utilizing an ideal startup mechanism as compared to the traditional startup procedure.</p>

With fast and prosperous development in communication technology, desktop or mobile devices may be equipped with wired and wireless network interfaces. Hence, users need a multihoming technique to help them making use of the network in- terfaces effectively. The Stream Control Transmission Protocol (SCTP) is a new transport protocol approved by the SIGTRAN Working Group of IETF (Internet Engineering Task Force) as RFC 2960 in October 2000 where it includes this useful characteristic. However, this feature may lead to some secure pitfalls. In this thesis, we come up with some approaches to improve SCTP against some existing tough problems raised from multihoming and provide more sufficient protection methods based on cryptography. Finally, a comparison of the existing security solutions is also given to demonstrate our contributions.

Cette thèse présente une solution pour améliorer la mobilité des réseaux, dans le cadre de communications véhiculaires ainsi que pour la distribution de contenu. Les solutions actuelles pour les communications véhiculaires (c'est-à-dire lorsqu'un réseau est mobile) reposent sur la mise en place de tunnels, permettant également d'utiliser simultanément les différentes interfaces disponibles sur le véhicule (multi-homing). Même avec des tunnels, ces solutions ne sont pas en mesure d'équilibrer le trafic sur les interfaces réseau disponibles, elles ne parviennent pas à tirer partie du multi-homing. De plus, certaines des solutions existantes pour la mobilité de réseau cachent la mobilité aux hôtes connectés au routeur mobile. De fait, cela empêche les hôtes de participer aux décisions relatives au multi-homing, telles que le choix de l'interface réseau à utiliser, ce qui est pourtant utile pour réaliser du routage à moindre coût. Dans cette thèse, nous proposons de combiner un protocole de mobilité réseau (tel que NEMO) avec le protocole de TCP-multivoies (MPTCP), ce qui permet aux nœuds hôtes de participer à la mobilité et au multi-homing. Cette nouvelle combinaison améliore significativement le routage et l'encapsulation de paquets causée par les tunnels. En outre, cela augmente le débit, la tolérance de panne, le temps d'aller-retour et réduit le délai de transmission. La deuxième contribution de ce travail propose une solution de continuité de session pour la distribution de contenu dans les réseaux 5G. Dans le réseau 5G, les équipements d'accès IP seront au plus proche des nœuds terminaux afin d'améliorer l'expérience utilisateur et de réduire la charge de trafic dans le réseau central. Le fait est qu'à un instant donné un terminal ne peut être raccordé qu'à une seule passerelle (SGW/PGW) à la fois. Et comme la passerelle change lors de la mobilité, les sessions en cours seront rompues, impactant les applications temps réelle, le streaming vidéo, les jeux, etc. Pour cela, la thèse présente une solution de continuité de session avec l'aide de TCP-multivoie en bénéficiant du fait que les serveurs de contenu sont stationnaires. / This thesis presents a solution for boosting network mobility in the context of vehicular communications and content distribution in fixed network. Existing solutions for vehicular communications (i.e., network mobility), relies on tunneling in order to use multiple available interfaces on a vehicle. Even with tunnels, these solutions are unable to balance the traffic over available network interfaces thus do not reach the goal to provide optimum multi-homing benefits. Moreover, some of the existing solutions for network mobility, hide the mobility from the hosts connected to the mobile router. This in result inhibits the host nodes from participating in multi-homing related decisions such as interface selection which can be helpful in performing least cost routing. In this thesis, we propose to combine network mobility protocol with MPTCP which enables the host nodes to participate in mobility and multi-homing. This novel combination significantly improves routing and tunneling packet overhead. Moreover it increases throughput, fault tolerance, round-trip time and reduces transmission delay. The second contribution of this work is providing a solution for session continuity in context of content distribution in 5G networks. In 5G network, the IP edges will be closer to the host nodes in order to improve the user experience and reduce traffic load in the core network. The fact that a host can only be connected to a single gateway (SGW/PGW) at a time, would break the ongoing sessions for real time applications like video streaming or gaming during an occurrence of mobility event requiring gateway relocation. The thesis presents the solution for session continuity with the help of multipath TCP by benefiting from the fact that the content servers are stationary.

More and more so-called soft real-time traffic is being sent over IP-based networks. The bursty, data-limited traffic pattern as well as the latency requirements from this traffic present challenges to the traditional communication techniques, designed for bulk traffic without considering latency. To meet the requirements from soft real-time traffic, in particular from telephony signaling, the Stream Control Transmission Protocol (SCTP) was designed. Its support for connectivity to multiple networks, i.e., multihoming, provides robustness and opens up for concurrent multipath transfer (CMT) over multiple paths. Since SCTP is a general transport protocol, it also enables for handover of media sessions between heterogeneous networks. Migrating an ongoing session to a new network, as well as CMT with minimal latency, requires tuning of several protocol parameters and mechanisms. This thesis addresses latency reduction for soft real-time traffic using SCTP multihoming from three perspectives. The first focus is on latency for signaling traffic in case of path failure, where a path switch, a failover, occurs. We regard quick failure detection as well as rapid startup on the failover target path. The results indicate that by careful parameter tuning, the failover time may be significantly reduced. The second focus in the thesis is on latency for signaling traffic using CMT. To this end, we address sender-side scheduling. We evaluate some existing schedulers, and design a dynamic stream-aware scheduler. The results indicate that the dynamic stream-aware scheduler may provide significantly improved latency in unbalanced networks. Finally, we target multihomed SCTP to provide for handover of a media session between heterogeneous wireless networks in a mobile scenario. We implement a handover scheme and our investigation shows that SCTP could provide for seamless handover of a media session at walking speed. / So-called soft real-time traffic may be sent over IP-based networks. The bursty, data-limited traffic pattern and the latency requirements from this traffic present a challenge to traditional communication techniques. The Stream Control Transmission Protocol (SCTP), with support for multihoming, was designed to better meet the requirements from soft-real time traffic. Multihoming provides for robustness and for concurrent multipath transfer (CMT) as well as for handover of sessions between heterogeneous networks. Still, to meet the timeliness requirements, tuning of protocol parameters and mechanisms is crucial. This thesis addresses latency reduction for soft real-time traffic using SCTP multihoming. The first focus is on signaling traffic in case of path failure, where a path switch, a failover, occurs. We show that careful parameter tuning may reduce the failover time significantly. The second focus is on signaling traffic using CMT. We address sender-side scheduling and show that dynamic stream-aware scheduling may reduce latency when data is transmitted over asymmetric network  paths. The third focus is multihomed SCTP for handover between heterogeneous networks, where we show that SCTP could provide for seamless handover of a media session at walking speed. / <p>Paper 3 (Efficient Scheduling to Reduce Latency...) ingick i avhandlingen som manuskript med samma namn.</p>

With the obvious evolution and acceleration of smart grid, it is crucial for its success to rely on a solid transmission protocol among its peripherals due to its real time streaming. TCP is the well known traditional transport protocol used for a reliable transmission, and is a major player for smart grid. However, it lacks a fault tolerance transmission method that overcomes potential failures which may mitigate smart grid progress and in its turn decrease its reliability. We propose that smart grid operators utilize SCTP as the principle transport protocol for their smart grid communications, by using the two very significant characteristics offered by SCTP multi-homing and multi-streaming respectively. Thus, we argue that they can override two major obstacles caused by TCP Head of Line Blocking (HLB) and the inability of handling automatically two or more paths to a final destination. Although SCTP resembles TCP in many aspects, SCTP can definitely play a dominant role in many current and future applications due to its key features that do not exist in TCP. We have used ns2.34 simulator as the tool whom we relied on to investigate whether or not smart grid may benefit over TCP by the two SCTP features, and have analyzed the output of simulated results by using other analytical tools. As we obtain results, we argue that smart grid operators should rely on SCTP as a feasible transmission protocol instead of TCP.

<p>Arbetet tar upp BGP-multihoming för mindre organisationer. Den jämför ett kommersiell alternativ mot open source-alternativ. Detta är för att se vad som krävs en av open source-lösning för ge konkurrens på routermarknaden, samt besparingar för organisationer som ska använda denna lösning.Praktiska och teoretiska jämförelser görs där Cisco-lösningar jämförs med OpenBGPD. Datan utifrån dessa tester används för att svara på problemfrågan. Sammanfattningsvis har open source produkter en fördel hårdvarumässigt på grund av lägre kostnader medan kommersiella har stora fördelar då de förlitar sig på nyare standarder.</p>

With the obvious evolution and acceleration of smart grid, it is crucial for its success to rely on a solid transmission protocol among its peripherals due to its real time streaming. TCP is the well known traditional transport protocol used for a reliable transmission, and is a major player for smart grid. However, it lacks a fault tolerance transmission method that overcomes potential failures which may mitigate smart grid progress and in its turn decrease its reliability. We propose that smart grid operators utilize SCTP as the principle transport protocol for their smart grid communications, by using the two very significant characteristics offered by SCTP multi-homing and multi-streaming respectively. Thus, we argue that they can override two major obstacles caused by TCP Head of Line Blocking (HLB) and the inability of handling automatically two or more paths to a final destination. Although SCTP resembles TCP in many aspects, SCTP can definitely play a dominant role in many current and future applications due to its key features that do not exist in TCP. We have used ns2.34 simulator as the tool whom we relied on to investigate whether or not smart grid may benefit over TCP by the two SCTP features, and have analyzed the output of simulated results by using other analytical tools. As we obtain results, we argue that smart grid operators should rely on SCTP as a feasible transmission protocol instead of TCP.

The Internet consists of thousands of autonomous networks connected together to provide end-to-end reachability. Networks of different sizes, and with different functions and business objectives, interact and co-exist in the evolving "Internet Ecosystem". The Internet ecosystem is highly dynamic, experiencing growth (birth of new networks), rewiring (changes in the connectivity of existing networks), as well as deaths (of existing networks). The dynamics of the Internet ecosystem are determined both by external "environmental" factors (such as the state of the global economy or the popularity of new Internet applications) and the complex incentives and objectives of each network. These dynamics have major implications on how the future Internet will look like. How does the Internet evolve? What is the Internet heading towards, in terms of topological, performance, and economic organization? How do given optimization strategies affect the profitability of different networks? How do these strategies affect the Internet in terms of topology, economics, and performance? In this thesis, we take some steps towards answering the above questions using a combination of measurement and modeling approaches. We first study the evolution of the Autonomous System (AS) topology over the last decade. In particular, we classify ASes and inter-AS links according to their business function, and study separately their evolution over the last 10 years. Next, we focus on enterprise customers and content providers at the edge of the Internet, and propose algorithms for a stub network to choose its upstream providers to maximize its utility (either monetary cost, reliability or performance). Third, we develop a model for interdomain network formation, incorporating the effects of economics, geography, and the provider/peer selections strategies of different types of networks. We use this model to examine the "outcome" of these strategies, in terms of the topology, economics and performance of the resulting internetwork. We also investigate the effect of external factors, such as the nature of the interdomain traffic matrix, customer preferences in provider selection, and pricing/cost structures. Finally, we focus on a recent trend due to the increasing amount of traffic flowing from content providers (who generate content), to access providers (who serve end users). This has led to a tussle between content providers and access providers, who have threatened to prioritize certain types of traffic, or charge content providers directly -- strategies that are viewed as violations of "network neutrality". In our work, we evaluate various pricing and connection strategies that access providers can use to remain profitable without violating network neutrality.