The rapidly increasing expansion and popularity of the Internet makes more and more users accept web service type. The web server with single server architecture is no longer satisfying a large number of user requests. The web cluster architecture becomes another batter solution. In our previous work, our laboratory has implemented a prototype of layer7 web switch, which provides content-aware land balancing. We also designed and implemented a management system to provide a easy way for system configuration. With the increasing of web technologies, most of web sites supply ¡§session-aware¡¨ service type. The session is that clients and servers that wish to exchange state information to place HTTP requests and responses within a lager context. In this paper, we propose a session-aware management in the web cluster. Base on our management system, we design a fault tolerance and QoS policy with session to improve performance and reliability of our web cluster system.

This paper describes an adaptive service differentiation scheme for QoS enhancement in IEEE 802.11 wireless ad-hoc networks. Our approach is called Dynamic Age-Dependent Backoff (DADB) which is derived from the ADB scheme and aims to improve the ADB scheme when the traffic load is high. Improvement of our scheme are provisioned by adjusting the size of the persistent factor of high traffic categories taking into account both age time of frame and network conditions. We evaluate the performance of DADB through simulations and compare it with the ADB scheme proposed in the 802.11e. Results show that our scheme DADB is similar to ADB scheme which can improve the delay and jitter in wireless network. Especially at high traffic load conditions, DADB outperforms the basic ADB: our scheme improve the throughput of high priority traffic category and decrease collision rate when traffic load is heavy.

In response to the presence of portable devices and the change in usage patterns, mobility support for computer networking has received increasing attentions in recent years. There has been wide variety of established works focusing on the shortening of the handover delay. Most of them had tried their best in maintaining the connections to their peer nodes as mobile nodes moving across different network domains. This might not be a best policy in certain applications, such as homogeneous content distribution systems. A new handover scheme incorporating anycasting and service migration is developed and presented in this thesis. In the proposed approach, anycast is used to locate a new nearest server as a mobile node entering a new domain, and an ongoing service will be dynamically migrated from a distant server to a new server with shorter weighted network distance to the client. As a result, the individual service connection, as well as the global network environment, will benefit from the service migration, in terms of improved service quality and bandwidth utilization.

With the rapid development of Web-based technologies, our daily life has become intensely involved with Internet. Combined with the maturity of wireless network technologies, the transmission of multimedia data using mobile communication equipments will surely become the next step of Internet usage. More and more real-time data and massive amount of information are being transmitted on the Internet, making the bandwidth a scarce resource. To resolve the congestion of Internet, therefore, the efficient management and distribution of limited and valuable resource is more important than the enhancement of it. Our research posed a dynamic resource allocation method, which exploited the reward-penalty concept in order to find the most efficient allocation solution under the constraint of limited resources. The method enabled the users who need to use resource to achieve the necessary resources and their guarantee of quality. The system resource managers or service providers could make the best arrangement of their constrained resources and gain the highest reward through two essential procedures: Admission Control and Resource Allocation. Users themselves, on the other hand, ¡§smoothly¡¨ adjust the resource they had to match the resources they gained. Our algorithm provided existent users with what they requested while at the same time maximized the benefit of the system and made the most efficient arrangement of resources in regards to new requests. The consequences of simulation experiments showed that our system, which was based on reward-penalty model, is apparently superior to the so-called one based on reward model. The results also showed that CB method took users¡¦ reward rate as well as their penalty rate into account while maintaining admission control.

The progresses of technology bring up the bandwidth of the network, that can afford the increasing data amount from text to multimedia and make the network application development change with every passing day and become more varied. Recently, the rising of the wireless network attracts the public¡¦s attention. Compared with the traditional network, the wireless network has the advantage in its convenience and extensibility, but it has shortcoming in its bandwidth and stability. Because of the limited resources of the wireless network, introducing QoS (Quality of Service) can use the resources more efficiently. QoS guarantee the ability to achieve the special network applications¡¦ requests by using the network components or technology. QoS can differentiate between different classes of network services and allocate the system resources much better. Our research adopts the reward-penalty model to differentiate between different kinds of service requests to maximize the system¡¦s earning. It is decided by three QoS parameters, reward rate, delay penalty rate and drop penalty. In the reward-penalty model, the admission control¡¦s goal is to maximize the system¡¦s benefit. The purpose of our research is to design an efficient and dynamic resource allocation method, including admission control and resource allocation, to find the most efficient solution under the constraint of limited resources and smoothly adjust the resources of the existing users to promise the QoS. The consequences of simulation experiments show that MDI, posed in our research, has a better performance than other algorithms. Under different network environments, e.g. arrival rate, request bandwidth, transmission time, MDI is better and more stable than other algorithms. MDI can adjust QoS parameters, e.g. reward rate, delay penalty rate, drop penalty, to achieve different system¡¦s goal, like low delay rate or low drop rate. Thus it can be seen that MDI is able to not only make an efficient use of system resources but also adjust the QoS parameters to counter the change of the network environment in order to have a better performance.

Este trabalho teve por objetivo estudar aspectos de Qualidade de Serviço (QoS) na transmissão de áudio e vídeo por redes de grande abrangência geográfica (WANs). Dois cenários distintos foram estudados. No primeiro foi feita uma proposta de um método de gerenciamento que permite que computadores de uma rede local (LAN) equipados com interfaces Ethernet possam criar canais dinamicamente através de um backbone ATM para tráfego de voz e vídeo. Uma implementação do modelo foi avaliada para ilustrar a viabilidade do método proposto. No segundo cenário foi mostrado através de extensas simulações computacionais que o princípio da deflexão pode ser usado com êxito para oferecer QoS a aplicações em tempo real. Nestas simulações foi usado como exemplo prático uma aplicação de voz sobre IP (VoIP).

The issue of converged networks is to ensure the sufficient quality of services along the entire length of the communication transmission. This issue is closely connected to the real-time services, such as VoIP (Voice over Internet Protocol) and videoconferencing. These services require strict adherence to quality parameters, otherwise their function is not guaranteed. This problem particulary resolves subsystem IMS (IP Multimedia Subsystem), which concluded on the basis of user profiles can provide the required quality of service. Therefore the theoretical part deals with the description of the structure of the system and protocols designed to signal the network. Various mechanisms to support quality of services in access and backbone networks are also described. The following section explains the principle of provision of quality requirements of end-user networks. In the practical part is this theoretical knowledge used for designing and configuration of the network consisting of various technologies. The resulting model is then simulated in Opnet Modeler program, which is used for designing and testing of packet networks. Each simulation shows the effect of mapping quality requirements in the different access network on technologies, which are supported in the backbone. The outcome of this work is detailed network analysis and comparison of mechanisms for implementing quality of service. The conclusion summarises all simulation outcomes.

This thesis describes the approach in designing and implementing a driver marking network traffic for quality of service provision. In the beginning distinct technologies usable for the driver development are discussed and compared to each other while the most suiting candidate is chosen for driver development. Next the thesis discusses the design of the driver according to specification and depicts a list of more specific requirements affecting the driver design itself. The focus point in design is the least possible impact on network traffic performance and the running system itself. In addition to the driver an application programming interface usable from user mode is designed and so the system as a whole ensures the marking of network traffic entirely. In the end the created driver architecture is described and the application programming interface is described in terms of use.

No

Since supplying passenger safety is the fundamental purpose of establishing vehicular ad hoc networks, researchers are mainly concerned with giving a strategy to ensure meeting this demand. Rescue services vehicles are one of the primary components of VANET, and the messages they broadcast play a vital part in delivering safety. As a result, offering a routing protocol algorithm that prioritizes their messages and guarantees QoS is one approach to meet the core purpose of VANET, or in other words, safety. Grouping the vehicle nodes, also known as clustering, is one of the appropriate solutions for improving the performance of the routing protocol. Most traditional cluster-based topologies in VANET solely consider the mobility to pick the cluster head. While cluster head speed fluctuations can affect the number of cluster head choices and improve the VANET QoS. Furthermore, the fast movement of vehicles exposes clustering links to vulnerability and directly impacts reliability. In this research, we proposed a new efficient multi-hop cluster-based routing protocol that prioritizes emergency vehicles' messages and provides stable and reliable communications to ensure emergency messages are delivered effectively. The number of neighbors, the distance between the vehicle and BS, and the S/N power received by the base station (BS) are the criteria for selecting a cluster head (CH) in our proposed model. Each CH is in charge of transmitting data from other cluster members to the infrastructure directly or indirectly through the qualified adjacent cluster heads. The epigenomic workflow approach is employed in our design to establish efficient resource management in RSU computing nodes and decrease transmission latency. The transmitted messages from vehicles are divided into two separate queues (q1 and q2), while the priority message queue uses the TDMA protocol to disseminate. In this thesis, experiments and simulations were carried out utilizing the NS-2 tool with VanetMobisim integration to assess the efficacy of the suggested approach. Achieved results indicate that the proposed technique increases communication reliability and stability while improving QoS for messages provided by rescue services.