主動延遲控制之傳輸控制協定

Abstract

主動延遲控制 (Active Delay Control) 是我們所提出的一個新的控制傳輸協定 (Transmission Control Protocol (TCP)) 的改良方法，我們在端點 (endpoints) 延遲封包的傳輸以改善 TCP 的效能。延遲的時間多寡可以由路由器依據擁塞程度或者由端點依據所收到的擁塞信號來作決定。在多條 TCP 搶用一條有限頻_的線時，Active Delay Control 可以將這些 TCP 的傳輸速率有效降低，不會像現在的 TCP 一樣造成很多的 timeout。所以 Active Delay Control 對一些生命週期很長而且不能忍受 timeout的 TCP 應用，如影像串流 (video streaming) 和儲存網路 (storage network) 是很有用的。此外，對一些生命週期較短，而且需要很快有效傳輸的 TCP 應用，如 HTTP，Active Delay Control也是很有用的。我們在本文中說明 Active Delay Control 的源由與概念，並藉由模擬分析其效能。

Active Delay Control is a novel extension for TCP, where TCP endpoints impose delays on the transmission of packets to improve TCP's performance. The amount of delay can be calculated by routers based on the level of congestion, or by endpoints based on the received congestion signal. When there are many TCP flows competing for the bandwidth of a link, Active Delay Control mechanism can reduce their transmission rates to arbitrary degrees by increasing delays, without experiencing timeouts as in today's TCP. This mechanism is useful for those long-lived TCP-based applications that can not tolerate timeouts including video streaming and storage networks. This mechanism is also useful for short-lived flows that require short transfer time, such as HTTP transactions. This thesis presents the concept and motivation behind Active Delay Control and performs analysis and simulations.