基於自我相似性的DWDM網路架構之研究

Abstract

由於一條單模光纖能夠藉著DWDM 技術同時傳送數百個波長，不僅大幅增加傳輸容量， 也為光網路帶來無窮的潛力。WDM 網路一直是大家很感興趣的研究課題，並且已有許多 不同的網路架構曾被探討。最近我們提出一個混合分封交換和波長路由的網路架構， 利用分封交換的高效率加上波長路由的簡單性，以建構一個既簡單且高效率的WDM 網 路。我們的想法源於自我相似性(self-similarity) --- 是數學界的碎形幾何或計算 機科學裡的自動機理論的主要觀念 --- 即一個簡單的型態，若在同一個階層能夠水平 重複使用，並且在不同階層也能垂直重複使用，最後會成為一個內在簡單外在複雜的 結構，並足以涵蓋各種複雜的問題。我們將自我相似性應用到多階層DWDM 網路，利用 一個簡單的網路形態和一個有效的波長處理方法以整合不同的網路階層。 之前我們考慮的是同質(homogeneous)的WDM 網路，其中每個節點的特性完全相同。由 於實際網路的節點在資料量及地理分佈上都有很大的差異，因此之前的結果並不能簡 單應用到實際網路中。 本計劃擬藉著設計更富彈性的網路型態與切合實際的波長處理 方法(包括波長指定，波長路由，波長重複使用，波長交換與波長轉換)，以延伸我們 的想法到實際網路中並且能包容實際網路的複雜性。此外，我們將進行理論分析以瞭 解所提網路的效率，以及其容量與限制。本計劃無疑將使我們所提出的架構更具實用 性，而其結果將有助於建構未來高容量DWDM 網路。

The capability of simultaneously carrying hundreds of wavelengths via DWDM technology not only significantly extends the transmission capacity of single-mode fibers, but also brings a lot of potential in optical networking. WDM networks had attracted much research interest, and various network architectures had been studied. Recently we proposed a hybrid packet-switching/wavelength-routed WDM network architecture, which aimed at combining the efficiency of packet switching and the simplicity of wavelength routing to be a simple and efficient high-speed network. Our idea originated from self-similarity – the key concept in the field of fractal geometry in mathematics or cellular automata in computer science -- that if a simple structure can be reproduced horizontally on the same level and vertically on different levels, it eventually becomes a complicated structure and is able to accommodate related complexity. We applied self-similarity to multi-level DWDM networks to integrate different network levels by the same topology and the same wavelength management scheme. Previously we studied a homogeneous WDM network with uniform node characteristics and designed a simple network topology and a wavelength management scheme for all network levels. However, the results may not be easily applied to practical networks with varied traffic volumes and geographical distributions. Here we will further extend our research to practical networks by designing a flexible network topology and a more practical wavelength management scheme(including wavelength assignment, wavelength routing, wavelength reuse , wavelength switching and wavelength conversion), so that our results will be able to accommodate varied requirements in practical networks. Moreover, we will carry out theoretical analysis to demonstrate the efficiency of the proposed network architecture, as well as its maximum capacity and limitations. It is no doubt that his project will enhance the applicability of the proposed architecture, and the result will benefit the construction of future high-capacity WDM networks.