臺灣博碩士論文加值系統

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.

1 Introduction
2 Background
2.1 TCP Splicing
2.2 Optimizing TCP Forwarder Performance
2.3 Asymmetric TCP Splicing
2.4 General Fields for IP/TCP Header Altering
2.5 Summary
3 Switched and Split Connection Splicing
3.1 Concept
3.2 Architecture
3.3 Algorithm
3.3.1 Enable SSCS
3.3.2 Process Spliced Connection
3.3.3 Handling ACK
3.3.4 Disable SSCS (Un-splice)
3.3.5 Buffer requirements
4 Implementation
4.1 Introduction to NetBSD
4.2 Implementation Overview
4.3 Changing in the Kernel
4.3.1 Data Structure
4.3.2 Interfaces (API)
4.3.3 Data Movement Process
4.3.4 ACK Handling Algorithm
4.4 Using SSCS in Application Proxies
5 Evaluation
5.1 Test-bed
5.2 Single Bulk Transfer Test
5.3 Multiple Bulk Transfer Test
5.4 Tests on Variable Buffer Space
5.5 Summary
6 Conclusion
References

[1] M. Leech, M. Ganis, Y. Lee, R. Kuris, D. Koblas, L. Jones, “SOCKS Protocol Version 5”, RFC1928, March 1996.
[2] J. Postel, J.K. Reynolds, “File Transfer Protocol”, RFC 959, Oct 1985.
[3] T. Berners-Lee, R. Fielding, H. Frystyk, “Hypertext Transfer Protocol — HTTP/1.0”, RFC 1945, May 1996.
[4] J. Postel, “Internet Protocol”, RFC 791, Sep 1981.
[5] J. Postel, “Transmission Control Protocol”, RFC 793, Sep 1981.
[6] David Maltz, “TCP Splicing for Application Layer Proxy Performance”, IBM Research Report RC 21139, March 1998.
[7] R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee, “Hypertext Transfer Protocol — HTTP/1.1”, RFC 2616, Jun 1999.
[8] Oliver Spatscheck, Jorgan S. Hansen, John H. Hartman, Larry L. Peterson, “Optimizing TCP forwarder performance”, IEEE/ACM Transaction on Networking (TON) Volume 8 Issue 2, April 2000.
[9] Saibal Kumar Adhya, “Asymmetric TCP Splicing: A Kernel Mechanism to Increase the Flexibility of TCP Splice”, Master Thesis of Dept. of CSE, Indian Institute of Technology, April 2001.
[10] “NetBSD homepage”, http://www.netbsd.org/