| Summary: | 碩士 === 國立中央大學 === 資訊工程研究所 === 90 ===
By interconnecting heterogeneous networks, the deployment scale of Internet is continuously expanding. Since distinct local communication systems may have different resources like capacities and bandwidths, and the IP datagrams store-and-forward processing of routers is usually in routing semantics, the end-to-end congestion control on the source and destination is necessary. The transport protocol over IP provides the mechanism. For example, TCP is designed for reliable data delivery with congestion avoidance.
However, for the multimedia streaming applications, the reliability requirement of TCP has some costs which are harmful to this kind of applications. These costs are, for example, the un-necessary delay to retransmit data, and the packets burst of sliding window-based scheme. Thus, it is necessary to have an alternative transport protocol using rate-based scheme and supporting the multimedia presentation profiles. RTP/RTCP suite is designed for these purposes, but there still are the critical research issues for multimedia streaming applications.
Two significant factors are the performance of longer periodic control, and the friendliness to TCP on the rate adjustment. To satisfy these two criteria, this dissertation proposes a rate estimation scheme based on the packets loss ratio and jitter ratio sampling at the RTP/RTCP-like receiver and using the time-based TCP model. The ‘time-based’ model is a rate equation of time variables, while the existing model, says ‘packet-based’, is another equation of the variable of packets count. The meaning of the rate estimation is that for one connection of a particular sending rate, the receiver can closely estimate the average transmission rate of other TCP traffic flows in competition. If the rate estimation performs well, it can be the basis of rate adjustment and congestion avoidance.
This research contains the inferring of the time-based TCP model, the functionalities for sampling and analysis at receiver, and ns-2 simulation of fixed sending rate UDP under ideal and competition environments. The results show that this approach conducts good estimation. The time-based proposal addresses the drawbacks of existing proposals that even with TCP friendliness, their sending rates are not smooth, or they are not suitable for RTCP long periodic control. Other differences are the innovative model for TCP and the consideration of jitter information.
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