Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/19248
標題: 進階控制比例式服務品質保證網路下的封包平均延遲
Advanced Packet Average Delay Control in Proportional QoS Network
作者: 吳嘉鴻 
Hung, Wu Chia 
關鍵字: QoS;服務品質;DiffServ;Proportional Delay Differentiation;Packet Scheduling;差異式服務;比例式延遲差異;封包排程
出版社: 資訊科學研究所
摘要: 
Proportional DiffServ 是近年來被廣泛討論的QoS機制,它能夠調整各服務類別之間的服務品質比率,滿足各個等級的使用者,本篇論文針對 Proportional Delay DiffServ 的議題,改進幾個有關封包平均延遲的排程方法,以達到較高的效益。
改良式Proportional Average Delay 排程方法主要是根據PAD排程的缺點做改進而成。PAD排程能夠在長時間下維持各類別封包平均延遲的比例關係,但在短時間下無法保證高類別的封包一定比低類別的有較短的封包延遲,而改良式的PAD排程能夠解決這個問題,且依然在長時間下保持各類別封包平均延遲的比例關係。
本篇論文利用程式來模擬PAD、WTP、HPD排程及改良式PAD排程。我們發現改良式PAD排程不僅解決了PAD排程延遲異常的問題,且比WTP排程獲得較佳的延遲比率。對HPD排程來說,改良式PAD排程能夠針對網路實際的壅塞情形來選擇合適的封包輸出,也比HPD排程獲得較佳的延遲比率。除此之外,在網路負載分佈突然改變時,改良式PAD依然能夠使各類別的封包在短時間下獲得合理的延遲對待。

Proportional DiffServ is an extensively discussed QoS mechanism recently. It can be used to adjust the relative QoS difference between service classes based on the pre-specified quality differentiation parameters. In this paper, we study several existed packet schedulers about proportional average delay, and proposed a new packet scheduler, namely Predicted PAD scheduler, to overcome drawbacks known in these approaches, also to meet the proportional DiffeServ requirement betterly.
Predicted PAD scheduler is mainly an improvement over PAD to overcome short time scale misbehavior found in PAD. PAD scheduling can keep the ratio of packet average delay between all classes in long timescales perfectly, but it is known to exhibit a pathological behavior in short timescales. Predicted PAD scheduler can avoid this situation, yet still can keep the advantage of PAD scheduler.
An simulator has been developed and extended simulations have been made over several existed schedulers, which include PAD、WTP、HPD and Predicted PAD. From simulation we can show that Predicted PAD scheduler not only solves the pathological behavior of PAD in short timescale, but also gains better delay ratio than WTP schduler in long timescale. As comparing to HPD, Predicted PAD scheduler chooses suitable packets according to real network traffic instead of using fixed parameter as in HPD, and it also gains better delay ratio than HPD. Besides, when the load distribution of the network changes suddenly, it can ensure that all classes have their individual reasonable treatment with packet delays.
URI: http://hdl.handle.net/11455/19248
Appears in Collections:資訊科學與工程學系所

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