Re-engineering the transmission control protocol

The Transmission Control Protocol (TCP) is one of the pillars of the Internet as it has been used by most applications for data transport. The rapid developments in broadband Internet and mobile/wireless networks, however, posed new challenges where recent studies revealed that current TCP could quickly become the bottleneck to the ever increasing bandwidth available. This thesis investigated the fundamental limitations of existing TCP designs and developed new designs for two of the TCP’s core functions, namely startup and congestion control. First, we proposed a novel approach called Stateful-TCP where path bandwidth is estimated in a previous flow for use in the Start-up phase of the subsequent flow to the same destination. This eliminates the need for bandwidth probing in conventional Slow-Start and enables TCP to efficiently utilize the available path bandwidth right from the beginning. For example, applying Stateful-TCP to Cubic - the current dominant TCP implementation, improved its performance by over 50% in terms of flow completion time. More importantly, Stateful-TCP can be applied to most existing TCP implementations as well as future designs. Second, we developed a new TCP design called Fast Launch with Agile congeStion Handling (FLASH) that not only improved performance for long TCP flows, but also achieved significantly better performance for shorter TCP flows which are more commonly found in the Internet. For example, Internet experiments with 1MB flow size showed that FLASH can reduce the flow completion time by 40% to 70% compared to Cubic, and by 30% to 60% compared to Google’s BBR. Last but not least, Stateful-TCP and FLASH are complementary and thus could be combined for even higher performance. Moreover, both are entirely sender-based and are compatible with current TCP receivers, making them readily deployable in current Internet servers.TCP作為目前核心網絡協議之一，為多數應用提供數據傳輸服務。最近研究表明，快速發展的寬帶互聯網和移動/無線網絡帶來更快帶寬，使得TCP協議成為傳輸瓶頸。該論文調查了現有TCP設計的不足之處，並針對TCP的核心功能模塊，啟動和擁塞控制提出了新的設計方案。首先，我們提出一個新算法叫做Stateful-TCP，新流通過復用去往同一目的地歷史流的帶寬預測信息來調整其初始發送速率。這使得TCP擺脫了對傳統慢啟動的依賴，可以從開始就有效地利用帶寬。例如，通過把Stateful-TCP應用到目前最廣泛使用的Cubic算法上，流傳輸完成時間可以有效地減少50%。更重要的是，Stateful-TCP也可以應用於多數現有以及將來提出的算法上。其次，我們設計了另一個新算法叫做快速啟動及敏捷擁塞控制(FLASH)，它不僅可以提升長流的傳輸性能，而且對於目前互聯網中佔多數的短流來說收效尤為顯著。例如，在傳輸1MB大小的互聯網實驗中，相比於Cubic和BBR，FLASH能夠分別减少流傳輸完成時間達40%-70%和30%-60%。最後，Stateful-TCP和FLASH可以互補，結合二者有望帶來更好的傳輸表現。並且，上述兩個算法實現均基於發送方，接收方無需修改所以可以直接部署到服務器上，與現有網絡架構完全兼容。Guo, Lingfeng.Ph.D. Chinese University of Hong Kong 2020.Includes bibliographical references (leaves 133-136).Abstracts also in Chinese.Title from PDF title page (viewed on October 19, 2022)