Research On Packet Scheduling And Traffic Shaping In QoS Oriented IP Access Networks

This thesis is concerned with delivering the packets with the end-to-end QoS guarantee by the QoS oriented IP networks. Being one of the two available network architectures of IP-QoS, the Int-Serv network is able to guarantee QoS for the packet flow, but presents some requirements to the flow generated from the communication terminals. Before entering the QoS oriented network, the flow should perform traffic shaping, which curbs the traffic burst and controls the average bit rate but may cause extra delay. Similar to the Int-Serv network, the Diff-Serv network presents traffic requirements to the served flow too. Different from the Int-Serv network, the Diff-Serv network only guarantees QoS for the aggregates. Reasonable packet scheduling is needed to support QoS for the flows. Hierarchical scheduling, normally used to perform the link-sharing, can be adopted in this case.A novel hierarchical scheduler called HTPA was presented after discussing available scheduling models. HTPA means hierarchical token parameter allocation. HTPA performs traffic shaping as well as hierarchical scheduling. It appears good bandwidth utility and flexibility. The HTPA algorithm was inserted into the Linux kernel to realize the software access gateway. How to improve the performance of the software access gateway was discussed then.The Token Bucket Filter (TBF) is widely used for traffic shaping to curb the traffic burst and average rate. TBF is also the cell of the HTPA scheduler. The relationship between the queue length of TBF and the packet loss ratio was analyzed based on the working principle of TBF directly. The relations about parameter settings of TBF to guarantee the deadline index were then derived. The simulation was done based on a MPEG video sequence model, with the results supporting the theoretic achievements.Finally, an Ethernet access network, one of the broadband access network, was discussed. With the development of multimedia services, there exists a tendency to support QoS in this network. With the application of packet scheduling and traffic shaping, the end-to-end QoS can be achieved for multimedia services in such an QoS oriented Ethernet access network.