ATM網路上多重通訊協定之設計與製作

Abstract

愈來愈多的使用者要求更高的網路頻寬以及更低的網路延遲﹐而 ATM 的特性能符合這樣的要求。ATM Forum 為此制定了區域網路模擬(LAN Emulation) 的規格﹐使傳統網路(Legacy LAN) 的應用程式可移植到 ATM 網路上運作。然而區域網路模擬有一些基本的限制﹐例如﹕不同的區域網 路模擬之間必須經由橋接器(Bridge)﹐但橋接器容易造成擁塞( Congestion)﹐區域網路的廣播功能(Flooding Function) 浪費太多網路 資源﹐區域網路模擬也不支援 QoS (Quality of Service)等﹐以上這些 限制使得區域網路模擬的效率並不很高﹐而且也無法充分發揮 ATM 的特 性。多重通訊協定(Multiple Protocol Over ATM) 因而被提出來解決區 域網路模擬的限制。 在本論文中﹐我們在一個名為 VINCE (Vender Independent Network Control Entity) 的軟體平台上發展設計多重通訊協定的架構﹐並且定義 了一些控制訊息的格式(the Format of Control Message)。我們並將傳 統網路(Legacy LAN)﹐模擬的區域網路(Emulated LAN) 以及多重通訊協 定整合在一起。多重通訊協定架構的主要特性有﹕傳統 "OSI第三層以上" 的通訊協定可直接在 ATM 網路上運作﹐減少位址轉換的負擔﹐允許建立 端對端直接連接(End-to-End Connection)﹐可降低網路的延遲並提供可 確定的 QoS﹐多重通訊協定在網路層(Network Layer) 上更容易建立虛擬 網路(Virtual LAN) 等。多重通訊協定的架構(MPOA) 可提供比區域網路 模擬(LANE) 更高效率的服務。 An increasing number of customers requires LAN access with high bandwidth and low delay over long distances. The characteristic of ATM (Asynchronous Transfer Mode) can offer these needs. The ATM Forum makes the specification of LAN Emulation (LANE) over ATM. The goal of LANE is the transparent support of existing LAN applications to ATM switch. The LANE has some limits, such as; communication with different emulated LAN must via bridge, which will lead to congestion. The flooding function of LANE spends too much resource of ATM, and the LANE does not support QoS. All those limitations bring lower efficiency, and the characteristic of ATM does not fully exploit. To solve the limitations of LANE, the Multiple Protocol over ATM (MPOA) is proposed. In this thesis, we had implemented a MPOA model on a public-domain software, the Vendor Independent Network Control Entity (VINCE). Some control messages of MPOA for the trial also had been defined. In our system, the legacy LAN, emulated LAN and MPOA structure are integrated. The main benefits of MPOA such as the traditional "OSI layer 3" protocols can directly run on ATM, and it will reduce the overhead of address resolutnection, that can reduce the latency and provide guaranteed QoS. Furthermore, it could be easier using MPOA to implement virtual LAN based on network layer address. So, the MPOA can provide higher efficiency than LANE.