| As the fourth media, networks provide more forms of information for People with the development of modern network. Currently multimedia is developing fast, the network which based on IP has been the most important platform for multimedia technology. TCP is the main transport protocol on Internet. Its congestion control mechanism which based on window is the important guarantee for the stabilization of Internet. More UDP flows running on the network can make the unfairness distribution of network resources badly, and even lots of TCP flows "starved to death " or new congestion collapse.TCP's AIMD congestion control mechanism is very fit to the applications which must ensure reliable transmission but ignore the delay. While it is not fit to the real-time media, because the real-time media applications, such as the voice and video, are sensitive to delay but not sensitive to reliability, and also require the smooth sending rate. With the increasing applications of real-time multimedia, it has been the important task to research a kind of TCP-friendly transport control protocol which fit to the real-time flows and control the congestion effectively.At present there are two kinds of TCP-friendly congestion control protocol for real-time flows. One kind is based on the window, the other is based on the TCP throughput model. The sending rate of the former can emerge the biggish dithering and not fit to the applications of the real-time multimedia. So the congestion control mechanism based on the TCP throughput model has been put forward. In one of it, the TFRC algorithm which based on Padhye TCP throughput model has been the standard RFC 3448. The throughput of the algorithm changes slowly and fit to the applications of the real-time multimedia while maintaining TCP friendliness. In fact, the network congestion can inspected accurately only by the router. The ECN-based TFWMFC algorithm which based on Floyd TCP throughput adopts the router control policy is... |
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