La thèse s'intéresse au problème de la gestion de la fiabilité dans les réseaux par satellite basés sur la norme de diffusion DVB-S, pour des applications multipoints. En raison de possibles fluctuations des conditions de propagation, le service offert par le lien satellite n'est pas garanti. Le cas échéant, il doit être complété par un service de niveau transport, contraint à limiter l'utilisation de la voie de retour en raison du nombre potentiellement élevé de récepteurs. La première problématique étudiée concerne les concepts à envisager pour concevoir une architecture protocolaire appropriée. L'architecture prévoit de reconsidérer l'utilisation des contrôles d'intégrité des données, et de renforcer la fiabilité sur les en-têtes des différentes couches protocolaires. Ce mécanisme est appelé Multi Protocol Header Protection. La réalisation de ces concepts est également étudiée. Elle est proposée dans le cadre de la méthode Ultra Lightweight Encapsulation permettant la livraison de datagrammes IP par les réseaux DVB. L'exploitation de l'architecture pour deux services de fiabilité est ensuite discutée au niveau des protocoles de transport. Le premier service, appelé fiabilité binaire non contrôlée, peut être offert pour des applications tolérantes aux erreurs binaires. Des simulations démontrent l'intérêt de l'architecture pour ce service. Pour un service de fiabilité totale, l'élaboration d'un procédé de fiabilisation adapté à l'architecture est étudiée. Le procédé fait intervenir un algorithme de décodage FEC adapté. L'évaluation globale de l'approche estime que pour un service identique, 5 à 30 fois moins de données peuvent être économisées comparativement à une architecture conventionnelle.

<p>The past few years have seen great increases in the use of portable devices like laptops, palmtops, etc. This has also led to the dramatic increase demand on wireless local area networks (WLAN) due to the flexibility and ease of use that it offers. Mobile IP and handover are important issues to be considered as these devices move within and between different networks and still have to maintain connectivity. It is, therefore, imperative to ensure seamless mobile IP handover for these devices as they move about.</p><p>In this thesis we undertake a survey to describe the real processes involved in mobile IP handover in WLAN environment for different scenarios. Our work also identifies individual sources of delay during the handoff process, the sum total of which makes up the total latency. Other factors that could militate against the aim of having a seamless handoff in an inter-subnet network roaming were also considered as well as some proposed solutions. These factors are security, packet loss and triangle routing.</p>

No description available.

<p>Utvecklingen av IP-telefoni har under de senaste åren gått fort fram och idag kan en hel IP-lösning utformas efter ett företags specifika behov. Syftet med uppsatsen är att ur ett tekniskt, socialt och ekonomiskt perspektiv undersöka tre företags införandeprocess av skilda IP-lösningar för kommunikation. Detta har vi gjort genom intervjuer med personer på CC-Systems, Softcom och ICA. Vi har kommit fram till att valet av IP-lösning och dess funktioner beror på företagets verksamhet och dess behov. Företagen använder beroende av införandets omfattning och teknikens komplexitet olika strategier för att etablera tekniken i företaget och detta har gjorts olika framgångsrikt. Framför allt är det tekniska problem och de anställdas acceptans till tekniken som försvårar införandeprocessen. IP-lösningen har påverkat företagen, dels genom ett förändrat arbetssätt för de anställda, men även genom att införandet har bidragit till nya möjligheter och ekonomiska besparingar.</p>

Utvecklingen av IP-telefoni har under de senaste åren gått fort fram och idag kan en hel IP-lösning utformas efter ett företags specifika behov. Syftet med uppsatsen är att ur ett tekniskt, socialt och ekonomiskt perspektiv undersöka tre företags införandeprocess av skilda IP-lösningar för kommunikation. Detta har vi gjort genom intervjuer med personer på CC-Systems, Softcom och ICA. Vi har kommit fram till att valet av IP-lösning och dess funktioner beror på företagets verksamhet och dess behov. Företagen använder beroende av införandets omfattning och teknikens komplexitet olika strategier för att etablera tekniken i företaget och detta har gjorts olika framgångsrikt. Framför allt är det tekniska problem och de anställdas acceptans till tekniken som försvårar införandeprocessen. IP-lösningen har påverkat företagen, dels genom ett förändrat arbetssätt för de anställda, men även genom att införandet har bidragit till nya möjligheter och ekonomiska besparingar.

This thesis investigates distributed router architectures and IP networks with centralized control. While the current trend in IP-router architectures is towards decentralized design, there have also been research proposals for centralizing the control functions in IP networks. With continuous evolution of routers and IP networks, we believe that eventually IP networks in an autonomous system (AS) and a distributed router might converge into one network system. This system, which can be considered both as a distributed router and a centrally-controlled IP network, is divided into a control plane and a forwarding plane. The control plane is responsible for routing, management and signalling protocols, while the forwarding plane is responsible for forwarding packets. The work in this thesis covers both the forwarding and control planes. In the forwarding plane, we study network processor systems that function as forwarding elements in a distributed router. We introduce a system model and a simulation tool based on the model. Using the simulation tool, we investigate network processor system design by studying throughput, utilization, queueing behavior and packet delays. In addition to network processor systems, we study IP-address lookup, which is one of the key packet processing functions in Internet routers. Our work in IP-address lookup contains an efficient lookup algorithm, a scheme to divide the lookup procedure into two-stages in a distributed router, and an approach to perform efficient lookup on a router supporting multiple virtual routers. In the control plane, we study three emerging research issues with centralized control. We provide a thorough study of the routing convergence process in networks with centralized control, and compare it with decentralized link-state routing protocols. We propose an efficient approach to perform traffic engineering and routing in networks with centralized control, and compare it with an approach using optimized link weights. Finally, we present an approach to perform loop-free updates of forwarding tables when the forwarding paths change. This loop-free update approach is particularly useful in networks with centralized control. The results presented in this thesis are useful for building next-generation routers and IP networks with centralized control that might eventually converge into one network system. / QC 20100726

The current Internet design is based on a best-effort service, which combines high utilization of network resources with architectural simplicity. As a consequence of this design, the Internet is unable to provide guaranteed or predictable quality of service (QoS) to real-time services that have constraints on end-to-end delay, delay jitter and packet loss. To add QoS capabilities to the present Internet, the new functions need to be simple to implement, while allowing high network utilization. In recent years, different methods have been investigated to provide the required QoS. Most of these methods include some form of admission control so that new flows are only admitted to the network if the admission does not decrease the quality of connections that are already in progress below some defined level. To achieve the required simplicity a new family of admission control methods, called end-to-end measurement-based admission control moves the admission decision to the edges of the network. This thesis presents a set of methods for admission control based on measurements of packet loss. The thesis studies how to deploy admission control in an incremental way: First, admission control is included in the audiovisual real-time applications, without any support from the network. Second, admission control is enabled at the transport layer to differentiate between elastic and inelastic flows, by embedding the probing mechanism in UDP and using the inherent congestion control of TCP. Finally, admission control is deployed at the network layer by providing differentiated scheduling in the network for probe and data packets, which then allows the operator to control the blocking probability for the inelastic flows and the average throughput for the elastic flows. The thesis offers a description of the incremental steps to provide QoS on a DiffServ-based Internet. It analyzes the proposed schemes and provides extensive figures of performance based on simulations and on real implementations. It also shows how the admission control can be used in multicast sessions by making the admission decision at the receiver. The thesis provides as well two different mathematical analyses of the network layer admission control, which enable operators to obtain initial configuration parameters for the admission decision, like queue sizes, based on the forecasted or measured traffic volume. The thesis ends by considering a new method for overload control in WLAN cells, closely based on the ideas for admission control presented in the rest of the articles. / QC 20100826

No description available.

The past few years have seen great increases in the use of portable devices like laptops, palmtops, etc. This has also led to the dramatic increase demand on wireless local area networks (WLAN) due to the flexibility and ease of use that it offers. Mobile IP and handover are important issues to be considered as these devices move within and between different networks and still have to maintain connectivity. It is, therefore, imperative to ensure seamless mobile IP handover for these devices as they move about. In this thesis we undertake a survey to describe the real processes involved in mobile IP handover in WLAN environment for different scenarios. Our work also identifies individual sources of delay during the handoff process, the sum total of which makes up the total latency. Other factors that could militate against the aim of having a seamless handoff in an inter-subnet network roaming were also considered as well as some proposed solutions. These factors are security, packet loss and triangle routing.

The final thesis named Tracking in Sensor Networks was created by the company Instrument control Sweden. The thesis work is to create a plug-in to an already developed software pro- gram, SkyView. Via the software program one should be able to control an IP-camera from AXIS, model 215 PTZ, with the appropriate protocol over a network.  An Application Programming Interface, API, was used to easily control the camera through SkyView. The interface is called VAPIX and is used to all cameras from AXIS. VAPIX sup- ports Hyper Text Transfer Protocol, HTTP, and Real Time Streaming Protocol, RTSP.  The video was sent through the camera with RTSP, thus an investigation resulted in that the protocol was best suited at streaming video. Steering commands to the camera was sent via HTTP. A small program was written, which was then integrated to SkyView. Features to be able to control the camera with the keyboard, mouse and a joystick were implemented. Zoom, bright- ness, focus and some more features were also added. The problem with the delay should be dealt with as soon as possible.