The Study And Implementation Of Multicast Oriented QoS Mechanisms For High Performance Routers

The Internet is no longer a data service only network. With fast growing applications such as VoIP, video conferencing, network games and multimedia entertainment etc., the urge demand for higher and more predictable quality of service has been aroused. The network is expected to offer more than best-effort services with differential services for different applications. Furthermore, many applications like IPTV need multicasting technology support to achieve the economic usage of bandwidth. At the same time, the higher and higher traffic makes the network congestion a much more serious problem. Thus it becomes an urgent job to develop much more sophisticated QoS and multicasting technologies.Performing congestion control is one of the preconditions for the efficient QoS mechanisms. For years, lots of research efforts focus on the end-to-end congestion control. Recently, people realize that it is very important to apply efficient congestion control mechanisms on the intermediate network nodes such as high performance routers because they determine a large portion of the network performance. Many achievements has been made in related researches on congestion control technologies. But we think that to solve the QoS problem better, it is much more important to study and apply the overall QoS supporting mechanisms for the high performance routers systematically rather than applying the individual technology such as congestion control only. The performance bottlenecks will be solved better by integrating various technologies, algorithms, and other improvements together in every aspect resulting in the QoS problems.This dissertation studies the congestion control of routers first, and then discusses the high performance router QoS and its supporting mechanisms under the multicast environment in a differentiate service architecture. An efficient QoS processing mechanism, QoS_RESM, for a high performance router prototype is developed in which the hardware and software processing method are combined together. And a series algorithms has been proposed in the mechanism. This improves the routers'QoS capability efficiently.The QoS_RESM is build under the high performance QoS router model, MQ-Router in multicast environment. In QoS_RESM, the supporting policies of diffServ, the design methods of queues, the threshold mechanisms and flow control mechanisms, and the design of drop probability table supporting multicasting flows are provided. A new router flow control method is proposed which makes use of the global congestion information to avoid or alleviate the system congestion earlier. The new congestion control algorithm based on the router's global ports states information is design and implemented. A packets dropping policy is designed for the algorithm. The policy processes packets with various priorities differently by use of multi-threshold mechanism of the combination of queue thresholds and packets attribution thresholds. For the packets waiting for switching to the egress side of the router or outputting to the next node in the network, the dropping decision is made by the drop probability. A drop probability computing method based on the stability theory is provided.A new bandwidth management algorithm based on piped DiffServ flow is studied and implemented. This algorithm computes the drop probability according to the offered rate, the priority of the piped DiffServ flow and the system congestion degree. This can adjust the bandwidth of every flow to satisfy the QoS requirements.Two efficient QoS supporting mechanisms of MQ-Router based on parallel technologies are studied and implemented. The first is the network processor multithread parallel processing mechanism which impacts the packet processing rate, while the second is the parallel storage data access mechanism which impacts the system throughput.The congestion control algorithm, the bandwidth management algorithm, the parallel processing mechanism and the parallel storage accessing mechanism mentioned above are tested on the prototype system of a high performance router based on MQ-Router model. The test results indicate that these algorithms and mechanisms can not only improve the related characteristics individually, but also improve the router's overall QoS performance by integrating all those technologies together.The work of the dissertation is supported by the important project of National Science Foundation of China(NSFC) and the important project of National High-Tech Research (863) Program. The major results are successfully applied in developing the"New Generation Internet High Performance Router".