彈性分封環之高效能乏晰公平流速產生器

Abstract

彈性分封環(Resilient Packet Ring)是一種應用於高速都會區域網路的環狀網路架構，並且擁有容錯與高頻寬使用率等特性。在彈性分封環中，公平性、穩定性、和收斂時間等在壅塞控制中是很重要的議題。在本篇論文中，我們提出一個高效能乏晰公平流速產生器(FLFRG)，藉著乏晰運作機制產生一個準確的本地公平流速來抑制壅塞情況並且達成上述考量。所提出的機制，是由三個部份所組成，適應性公平流速計算器(AFRC)、乏晰壅塞偵測器(FCD)、與乏晰公平流速計算器(FFRC)。適應性公平流速計算器產生一個評估過的公平流速而乏晰壅塞偵測器根據次級傳輸緩衝器(STQ)的容納量與接收到的流量大小來指出當前的壅塞程度。乏晰公平流速計算器經由考量兩項由適應性公平流速計算器與乏晰壅塞偵測器輸出的結果來得到反映真實流量狀況的本地公平流速。藉由適應性公平流速計算器與乏晰壅塞偵測器的使用，乏晰公平流速產生器可產生較小的收斂時間，再者當與其它演算法相比，在不同大小的壅塞區域中皆獲得極好的效果。模擬結果顯示出我們所提出的方法，不管在公平性、穩定性、與收斂時間都上擁有傑出的效果。因此乏晰公平流速產生器不失為一個具可行性且十分吸引人的方法。

The resilient packet ring (RPR) is a ring based network for high-speed metropolitan area networks which has properties of fault tolerance and high bandwidth utilization. In RPR, the issues of fairness, stability, and convergence time are important in congestion control. In this thesis, we propose an effective fuzzy local fair rate generator (FLFRG) to achieve above considerations. FLFRG generates a precise local fair rate by fuzzy logics to suppress upstream traffic causing congestion. FLFRG is composed of three components: adaptive fair rate calculator (AFRC), fuzzy congestion detector (FCD), and fuzzy fair rate calculator (FFRC). AFRC produces an estimated fair rate and FCD indicates the congestion degree of local station according to STQ occupancy and arrival rate to STQ. FFRC adopts the two outputs of AFRC and FCD to generate a local fair rate which reflects the real traffic condition. Since AFRC and FCD are applied, the smaller convergence time than other fairness algorithms is obtained. Furthermore, even in different scales of congestion domain, FLFRG still has an excellent performance as compared with other fairness algorithms. Simulation results show that the proposed FLFRG has an outstanding performance on fairness, stability, and convergence time in different testing scenarios. Consequently, we can conclude that that FLFRG is a feasible and attractive design for congestion control in RPR.