通訊網路封包交換技術之研究

Abstract

在通訊網路的應用上，封包交換技術佔有相當重要的地位。他運作的的快 慢直接影響到資料在網路中傳輸所需要的時間。在這篇論文中，研究的主 題就是交換系統中封包交換技術與效能評估。基本上，我們探討了四種 Space-Division交換機的架構以及效能的分析。這四種交換機分別為the Knockout,the Sunshine,the Lee's,和the tandem banyan交換機。The Knockout是以N平方次散開路徑為架構的交換機，速度快但複雜度與成本 較高。至於其他三種則是使用banyan網路為主要結構的交換機。The Sunshine和the Lee's交換機是以Batcher排序器與 banyan網路為主要的 拓蹼學。前者在N較小的時候，成本低、速度快、元件少，但是不具模組 性且容錯能力差。而the Lee's交換機是種模組性的交換機，使用divide and conquer的方法來處理輸入資料。當N值或是負載較大時它是這四種交 換機中效能分析最好的一種。至於the tandem banyan交換機則是單純的 以banyan網路協力串接起來而成，架構方法相當簡單。此外，我們針對 the tandem banyan交換機的架構撰寫模擬程式來測量它的封包遺失機率 。而根據這些模擬的結果，我們可以明白得知封包遺失機率與負載、 banyan網路個數和輸入線的關係。進而當設計超大型積體電路的晶片時， 可以做出一個較好的取捨方式。另外，根據新的評估方向我們也討論了這 四種交換機的包裝成本。我們發現這四種Space-Division交換機在速度， 成本，模組性及容錯能力等因素的考量下，都有其各自的優點和缺點。對 於不同的交通量模式也各有其優劣之處。 It is well known that the technology of packet switching has played a very important role in the development of computer communication networks.The transit time of data transferred by switches is directly affected by the speed of the switches.In this thesis,we mainly study the basic principles and technology of packet switching in switching networks. We basically explore the architecture and performance analysis of four space- division switches.The architecture of Knockout switch is fabric with N^^2 disjoint path.Though its speed is high enough,its complexity and cost are higher than other switches.The Sunshine and the Lee's switches are composed of the Batcher sorters and the banyan networks.The advantages of Sunshine switch are low cost,high speed,and less components.The Lee's switch is a modular switch which processes the data from the input lines by the divide-and-conquer algorithm.While the value of N and load is large enough,we have found that the Lee's switch works better than the other three switches.As for the tandem banyan switch it is composed of banyan networks working in tandem. Moreover,We compute the packet loss probability in a tandem banyan switch by a simulation.According to the results of simulation,we can understand the relation of packet loss probability with load,the number of banyan networks,and the number of input lines.Hence,When designing the chip,the results of simulation can help us to make a better dicision. Furthermore, we also discuss the packaging cost of these four switches from a new measure viewpoint. We should point out that it is hard to single out any one of these four switches as the best in the consideration of speed, cost,modularity,and fault- tolerance.Under various traffic condi- tions,it seems that no single architecture is the most suitable switch for all traffic conditions.