擊出型ATM交換元

Abstract

對一個交換元來說，不論輸出入埠的數目多少，封胞同時到某個輸出埠的 機率，會隨其數目急遽減少。擊出型交換元利用此特性，只要集中器輸出 埠數目選擇得宜，就能達到一定的封胞遺失要求。為了減低集中器的複雜 度，許多以擊出型交換元發展出的架構被提出，他們運用了輸入埠緩衝區 和輸出埠群組的方法來減低集中器的輸出埠數目。在本篇論文中，我們利 用輸入埠群組的方法降低集中器的輸入埠個數，進而減低集中器複雜度。 雖然必須增加前置集中器，但整體複雜度仍大幅降低。輸入埠群組法可以 加上輸出埠緩衝區回饋和輸出埠群組進一步改良。經由模擬發現，加入出 埠群組對交換元複雜度減少比加入輸出埠緩衝區回饋更具效果。在相同的 封胞遺失率中，將輸入埠群組與輸出埠群組結合之架構，與其他以擊出型 為基礎之交換元做比較，輸入埠群組與輸出埠群組結合之架構所需的複雜 度最少，得到最佳的改善。 In the Knockout switch, it was observed that satisfactory cell lossperformance could be obtained with a modest number of concentrator output independent of the switch dimension. Several Knockout-based switch architectures have sinc been proposed in which techniques such as concentrator feedback with input buffering and output groupingwere employed to reduce the number of concentrator outputs, and hencethe complexity. In this paper, we propose the Knockout switch withgrouping (KIG) which pre-concentrates switch inputs in groups, and thus reduces the number of concentrator inputs. Such complexity reductionof concentrators greatly outweighs the overhead in pre- concentratorsbased on the estimated layout area. The KIG switch can be furtherimproved by employing output buffer feedback and output grouping. Itwas found that the KIG switch with output grouping (KIGOG) is capableof achieving comparable cell loss performance with less area comparing to theone with output buffer feedback. When comparing to other Knockout-based switches with the same output grouping factor and comparable performanceunder bursty traffic, the KIGOG switch requires the least layout area,which is less than one half of the Abacus switch, and is about one thirdof the Growable switch.