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標題: 點對點可用頻寬探測方法之研究
The Study of End-to-End Available Bandwidth Methodolog
作者: 林寯奭 
Lin, Chun Shih 
關鍵字: QoS (Quality of Service);可用頻寬(Available Bandwidth);初始封包對的間隔時間(initial gap);封包平均兩兩之間到達的時間差( average output gap)
出版社: 資訊科學研究所
可用頻寬對於服務品質(QoS)而言是一個重要的參考指標,因此一個可靠的網路可用頻寬探測機制是有必要的。近年來,IGI (Initial Gap Increasing)與PTR (Packet Transmission Rate)是兩種表現很好的可用頻寬探測技術,但此兩種方法的缺點是其利用漸進式增加傳送速率來適應目前網路可用頻寬的機制並不會有效減少探測時間與探測封包數量。故本研究提出一個演算法IGT (Initial Gap Tuning)來提升IGI/PTR探測方法之探測效率。
IGT演算法中傳送端傳送一連串探測封包至接收端,由接收端評估探測封包平均兩兩之間到達的時間差(average output gap),以此資訊作為初始封包對的間隔時間的設定,試圖以快速調整initial gap與average output gap能到達到一致,縮減演算法收斂時間。本研究實驗環境設計一個端點對端點的探測路徑,其路徑中加入穿插流量以揣摩真實網路環境。透過Network Simulator (Version 2.27)模擬軟體驗證,其結果證明本篇提出的演算法在探測過程中能以少量的封包測量可用頻寬,並有效地縮減收斂時間。

Estimating available bandwidth is a critical parameter of Quality of Service (QoS), it is necessary to provide a reliable probing technique to measure available bandwidth. Recently, IGI (Initial Gap Increasing) and PTR (Packet Transmission Rate) are popular approaches to estimate available bandwidth. However the convergence time and number of probing packets are gradually increasing with the transmission rate to adapt network bandwidth. So we propose an Initial Gap Tuning (IGT) algorithm to enhance the measuring efficiency of IGI / PTR.
In IGT algorithm, sender side sends a train of probing packets to receiver side, receiver evaluates the average output gap of probing packets and echoes back this information to sender setting up a new initial gap. The concept of IGT is trying to converge in a fairly short time scale when the initial gap equals to average output gap. We define an end-to-end path with cross traffic between the end host in order to simulate the real Internet environment and our method has verified through a simulation software (Network Simulator version 2.27), the experiment results indicate that IGT can use small amount of probing packets and efficiently reduce the convergence time to measure the available bandwidth.
Appears in Collections:資訊科學與工程學系所

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