多個子系統互連的交換結構之設計與製作

Abstract

一般而言，通訊節點是由一組執行不同功能的子系統所構成。子系統間藉 著交換資料與控制訊號以便達成通訊節點所要求的系統功能與目標。在一 個寬頻的通訊節點內以傳統的背板匯流排建構多個子系統間的互連，不論 在頻寬的需求與實體距離的限制上都不是很好的方法。吾人所提出的多個 子系統互連(Multi-subsystem Interconnection)技術，簡稱MSI，即是希 望以一種可調式的平臺設計來改善傳統背板匯流排的缺失，並促進多個子 系統間的資料交換與實體連結。MSI是架構在 ATM的交換技術上，而且是 製作在背板上。子系統記憶體內Level-2的資料可利用 MSI所提供的虛擬 通道做資料轉移的目的。MSI的核心是其交換結構與交換結構控制電路。 交換結構則擁有多重投射(Multicast)的優越性；細胞的尋徑控制電路會 比交換資料控制先一個細胞－時間做處理。這種導管式的設計法由於有相 對較多的時間來解決輸出端衝突的問題，所以可大大簡化了交換結構的電 路設計。以MSI為基礎的子系統除了有無虛耗的通訊、實體位置的彈性配 置等特性之外，子系統可以重複使用則是另一重要特色。MSI的應用相當 廣泛，包括有區域ATM交換機、LAN Superhub、高效能的路由器與橋接器 、和寬頻之頻寬管理。 Communication nodes are typically composed of multiple subsystems,each performing designated functions such as LAN interface, routing,format conversion, and high-level applications , etc.. Multiple subsystems are tightly coupled together to achieve the aggregated system functions and objectives by exchanging data and controls. Conventional backplane buses are uneffective means for the interconnection of multiple subsystems in broadband communication nodes,such as local ATM switches and super-hubs in Local Area Networks(LANs), because of the bandwidth inadequacy and physical distance constraint. The Multi-subsystem Interconnect(MSI)is intended as a scalable platform to facilitate the physical coupling and information exchange among multiple subsystems. The MSI is based on the fast-packet switching. Implemented on backplanes, it provides virtual channels for switching of level-2 information in sybsystems' memories , which are sent in 53 bytes packets by the MSI in hardware. The core of the MSI consists of a switching fabric and its control. The structure of the switching fabric provides multiple paths into each destination. Multi-cast is the inherent property of the fabric. Routing controls of packets are skewed to the switching fabric control one packet-time ahead. This pipe-line approach time constraint in performing any conflict resolutions,resulting simple logic design of the switching fabric control. The MSI subsystems will be highly reusable, in addition to having overhead-free communication and flexible physical interconnection capabilities. The MSI applications include local ATM switches, LAN superhubs, high performance bridges/ routers, and broadband bandwidth managers.