跨通訊層設計之部份可靠性TCP友好傳輸層吞吐量分析及最佳化

Analyzing and Optimizing Throughput of Partial Reliable TCP-friendly Transport with Cross Layer Design

張志華(Chih-Hua Chang)

指導教授 ： 鍾添曜

元智大學/資訊學院/資訊工程學系/碩士(2008年)

摘要

有時效性的多媒體資料在網際網路上的傳輸面臨了很多的挑戰，包括了多變化的傳輸延遲、網路擁塞以及封包遺失。當使用到802.11無線區域網路(WLANs)及TCP友好(TCP-friendly)傳輸層時，這些挑戰變的更加的嚴苛。在本論文裡，我們利用封包存活時間及調整重送次數限制的跨通訊層設計方式來確保資料的傳輸、改善傳輸層吞吐量以及減少點對點的封包遺失。藉由觀察到封包存活時間可以實現網路傳輸層級的截取自動重送機制(ARQ-Based)錯誤控制及根據通訊網路媒體層(MAC)的重送設定可以被最佳化，因此鏈結抹除或緩衝區溢位造成的整體網路封包遺失率可以減少。傳輸層的完整佇列模型也在本論文中探討，透過這個完整的佇列模型可以計算出點對點的延遲分佈及吞吐量。因此可以利用點對點的延遲分佈來評估在封包存活時間下的平均封包遺失率。透過這個模型我們可以在封包存活時間下設定重送次數來最佳化網路的吞吐量。

關鍵字

動態控制 ； 跨層級設計 ； TCP友好 ； 部份可靠性 ； 延遲限制 ； 無線區域網路

並列摘要

Abstract-Delivering multimedia data timely over Internet poses many challenges, including coping with variable transport delay, network congestion and packets losses. The challenges become even stricter when the data transport involves 802.11 wireless LANs (WLANs) and TCP-friendly is considered. In this thesis, we apply a cross layer design scheme that exploits the packet lifetime mechanism of SCTP and retry-limit adaptation at the link layer to ensure timely data delivery, improve transport throughput, and reduce end-to-end packet loss. The design of our method is motivated by the observation that the packet lifetime can realize transport-level truncated automatic repeat request (ARQ)-based error control and accordingly the retry limit settings of the MAC layer can be optimized such that the overall packet losses that are caused by either link erasure or network congestion are minimized. A complete queuing model for transport layer performance analysis is also developed, with which the end-to-end delay distribution and throughput can be calculated. The end-to-end delay distribution is then used to estimate the average packet loss rate with respect to a given packet lifetime. Using the model, we are able to choose retry limit at the MAC　layer for a given packet lifetime

並列關鍵字

Adaptive control ； cross layer design ； TCP-friendly ； partial reliable ； delay bound ； wireless LAN

參考文獻

[1] P802.11/D1, Draft Standard IEEE 802.11, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” November 1994

[2] M. A. Visser, “Performance Study of the IEEE 802.11 Wireless LAN Standard,” Master Thesis, Delft University of Technology, June 1995

[4] H. Balakrishnan, and S. Floyd, “A proposal to add explicit congestion notification (ECN) to IP,” RFC 2481, January 1999

[5] M. Liu and N. Ehsan, “Modeling and Analysis of TCP Enhancement over Heterogeneous Links,” International Conference on Networking, July 2001

[7] J. Postel, Transmission Control Protocol, RFC 793, September 1981