在不同擁塞控制的方法下之TCP效能分析與公平性改進

Abstract

在不同的擁塞控制的方法下，TCP Vegas明顯的優於現行最常被使用的TCP Reno，然而；當TCP Vegas的使用者在和TCP Reno的使用者競爭可用頻寬時，TCP Vegas很明顯的遠輸給TCP Reno，這也就是為什麼在網際網路的使用者裡，很少人採用TCP Vegas的最主要原因。

在這篇論文中，我們提出了一種方法，藉由我們估計出在路由器裡的連線數，動態的去調整RED裡的最低下限值和最高上限值，達到偵測出TCP Reno的連線封包，根據我們審慎的分析，TCP Vegas和TCP Reno是如何利用在RED路由器裡的緩衝空間，我們可以得知假使在RED路由器裡的緩衝空間能被適當的設定，那麼TCP Vegas將能夠有能力和TCP Reno競爭，我們用了分析和模擬實驗來評估公平性的問題，而且我們也證實了我們方法的可行性。

TCP Vegas outperforms the more widespread TCP Reno in congestion control. However, TCP Vegas sources show high weakness in taking the available bandwidth when competing with other TCP Reno sources. This is a major reason that hinders the spread of TCP Vegas among Internet users. In this thesis, we propose a method to modify the RED algorithm for detecting packets from TCP Reno connections, just simply dynamically adjusting the value of MinThresh and MaxThresh in RED Routers according to the number of connections we predicted. With a careful analysis of how Vegas and Reno use buffer space in RED routers, we will show that Reno and Vegas can be compatible with one another if the buffer in RED Router is configured properly. We use both of analysis and simulation experiment for evaluating the fairness, and validate the effectiveness of the proposed mechanisms.