UBC Theses and Dissertations
Receiver-driven layered multicast using active networks Cheng, Lechang
This thesis introduces a new scheme of receiver-driven layered multicast using active networks (RIM-AN). In order to address the problem of heterogeneity of clients, a layered multicast (RLM) scheme is used. In this method, the video is encoded into a set of layers and the client subscribes to cumulative layers according to their available bandwidth. In additional to the basic data dissemination scheme, a distributed TCP-friendly congestion control mechanism has been proposed. With the active nodes, the multicast tree is divided into a set of subsystems with a hierarchical structure and the sending node in every subsystem is regarded as a pseudo server. End-to-end congestion control is performed at each of the subsystems. In every subsystem, the receiver estimates the packet loss rate and round trip time of its upstream link and computes a fair transmission rate based on the TCP-throughput estimation function. It then calculates the subscription level and sends it to the pseudo server which will adjust the transmission rate accordingly. Simulation studies show that with the proposed congestion control mechanism, RLM-AN flows have smoother and more TCP-friendly throughputs and quicker response to congestion inside the network than RLM flows. In this thesis, a FEC-based error control mechanism is also presented for RLM-AN . The error control is performed on every subsystem. With the estimated packet loss rate, the receiver calculates the number of redundant packets for error recovery. It sends the information to the pseudo server which will dynamically adjust the error protection level. The intermediate active nodes will also perform error recovery to eliminate the error propagation problem. Simulation results show that the error control mechanism greatly reduces packet loss rate without increasing the error recovery latency significantly.
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