區域及都會網路中提供高服務品質的頻寬配置機制

Abstract

高速區域及都會型網路已廣為佈設以支援寬頻多媒體的應用。這些應用需 要服務品質（QOS）上的保證，如時間延遲(delay)、jitter、及單位傳輸 量(throughput)等等。為了提供這些品質上的保證，高速網路勢必具有頻 寬配置機制。此論文即是在其中的媒體存取控制層(MAC)及傳輸層中提出 應如何建立頻寬配置機制。首先，在MAC層中，我們提出一個新的控制協 定，名為—Prioritized Adaptive Cycle Cell Insertion (PACCI)。此 協定利用普通週期的頻寬，來提供公平的存取機會給所有的節點(包括客 戶端及伺服器)。再利用分配特殊的週期來提供額外的存取機會給負載重 的節點(如伺服器)。至於這兩種週期分配的比例則是根據一個頻寬配置機 制，為了提供不同的單位輸出量給客戶端及伺服器。經由模擬器的分析顯 示出頻寬配置機制的準確性以及PACCI的優越性。 其次在傳輸層，一種品 質保證的傳輸系統被提出，可用來支援三種應用的資料傳輸。此系統由一 個頻寬配置機制及傳輸協定模組所組成。頻寬配置機制會聰明的管理傳輸 層的頻寬。至於，傳輸協定模組則會對延遲敏感的應用執行以速度為基礎 的流量控制。而速度的多少則是由先前的頻寬配置機制所決定。此外對於 資料遺失敏感的應用則是提供嚴格的錯誤偵測措失。最後依據模擬的結果 顯示，此高服務品質的傳輸系統能對延遲敏感的應用提供保證的時間延遲 和jitter。但會使資料遺失敏感的應用造成些許的輸出量降低的現像。此 外，與TCP相比的結果也顯示出此傳輸系統能提供較小的最大系統延遲以 及jitter。 High speed LANs/MANs have been widely deployed to support broadband multimedia applications requiring the guarantee of Quality Of Servoce (QOS). For supporting QOS guarantee, bandwidth allocation mechanisms have been employed. This thesis aims at proposing bandwidth allocation mechanisms at both Medium Access Control(MAC) and transport layers in high speed LANs/ MANs, respectively. First, at the MAC layer, a new protocol, called Prioritized Adaptive Cycle Cell Insertion(PACCI), is proposed. PACCI offers prioritized access to privileged nodes(e. g., servers) and fair access to regular nodes (e.g., clients) through restricited cycles and regular cycles, respectively. The bandwidth allocation of the regular and restricted cycles is then based on an analytic model for QOS guarantee in terms of throughput. Simulation results are presented to demonstrate the accuracy of the analysis and the superior performance of PACCI. Second, at the transport layer, a QOS-guaranteed Transport System (QTS) is proposed to support three classes of applications. QTS, composed of a bandwidth allocator and a transport protocol module. The bandwidth allocator intelligently manages the allocationof transport-layer bandwidth. The transport protocol module of QTS performsrate-based flow control for delay-sensitive applications based on transfer rates predetermined by the bandwidth allocator. In addition, the module accomplishes error control only for loss-sensitive applications. As a result, as will be shown, QTS offers satisfactorybounded delays and jitters for loss-sensitive applications, Finally, we demonstratethe superiority of QTS over TCP via simulation results in terms of maximum and mean ystem delays, and delay jitter.