A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science, Schoool of Advanced Technologies

Thesis (Ph.D.) - Asian Institute of Technology, 2005

The Internet has been known to be a best-effort network that offers no provision for reliable data transfer or delivery time. Some Internet applications, however, have specific requirements for their transmission and demand a better quality of service (QoS) from the network. This study proposes a dynamic QoS, or D-QoS, model on IP networks where QoS settings can be automatically reconfigured based on the concept of active networks. The system allows authorized users to request network interruptions that allow their privileged flows to be optimally transmitted at the expense of other existing traffic. The requests are carried in the program part of each active packet and instruct each D-QoS node traversed to adjust the QoS settings for the interruption. At the completion of the privileged flow transmission, the network resumes its services for the flows that had been interrupted. Different levels of privilege can be granted to authorized users enabling multi-level interruption on D-QoS nodes, where a number of privileged flows can coexist. The D-QoS model can be incrementally deployed. A network administrator may consider positioning D-QoS nodes to ensure the transmission quality of the privileged flows initially at the links where bandwidth is tight, the bottleneck links. More D-QoS nodes may be added, at a later stage, to guarantee the flow performance along the transmission path. In this dissertation, the design of D-QoS with the proposed interruption mechanism and the QoS reconfiguration scheme are explained. The functions and the performance of the model are evaluated through experiments on a small prototype, and through simulations. The model has been shown to be able to dynamically adjust the network QoS configuration according to the requests of authorized users and to offer assurance for privileged flows with improved network utilization.