加速應用程式代理伺服器之可切換及分割之連線疊合技術

Abstract

傳統的應用程式代理伺服器使用TCP連線疊合技術加速其傳輸效能。TCP連線疊合技術在作業系統核心中提供一TCP層級的資料轉送，使得資料轉送的速度得以提升，同時降低系統CPU的使用量。但其缺乏足夠的彈性供各種不同類型的應用程式代理伺服器，同時對程式設計人員而言，使用此技術並不便利。因此我們提出一個「可切換及分割的連線疊合技術」，將連線疊合的動作提升至作業系統之TCP暫存區，如此不但可以提供近似於傳統TCP連線疊合技術之效能，同時大大改善其缺乏彈性及易用性的缺點。與未使用此技術的應用程式代理伺服器相比較，使用此技術可使得傳輸效能(吞吐量)提升70%，而CPU使用量只有原本的五分之一。

Traditionally, application proxies improve its forwarding performance by using TCP splicing. TCP splicing provides an in-kernel forwarding mechanism to increase forwarding performance and to reduce CPU utilization, but it lacks flexibility for supporting different uses and types of application proxies and introduces complexity for proxy programmers. Here we propose a new mechanism named switched and split connection splicing (SSCS) which splices two connections at the TCP buffer layer. It not only provides similar benefits to TCP splicing but also improves its flexibility and convenience of use. Compared to a non-accelerated proxy, in our TCP forwarding test, throughput increases by 70% and CPU utilization reduces to only one-fifth of that non-accelerated application proxy uses.