SSCOP協定於非同步傳輸網路UBR服務之速率方式流量控制方法

Abstract

Service Specific Connection-Oriented Protocol (SSCOP) 是一個用於 寬頻數位交換網路 (B-ISDN) 上ATM Adaptation Layer (AAL) 的新的通 訊協定。SSCOP 目前被使用於ATM訊務 (signaling) 控制上，然而除了訊 務控制，它也可以用來作兩端點 (end-to-end) 間的資料傳輸。因為 SSCOP的流量控制方法在規格上並無明確定義，所以在SSCOP能被使用在如 Unspecified Bit Rate(UBR) 網路環境中的資料傳輸之前，SSCOP必須具 備一個有效的流量控制方法。在本論文中，我們提出一個以資料傳輸速率 為基礎 (rate-based) 的流量控制方法, RB-SSCOP。我們希望藉由維持 bottleneck switch 的per-vc queue occupancy 在一個特定值，以提昇 網路的效能並使資料的傳輸能夠公平。經由分析SSCOP的控制機制，我們 利用數學推導出流量控制的規則。此外，RB-SSCOP還包含了兩個重要的基 本機制，Bottleneck Rate Probing (BRP) 和Bottleneck Queue Occupancy Estimation (BQOE) 機制。其中BRP 是用來測量connection分 享到的service rate，而BQOE則是用來估計bottleneck queue occupancy 的大小。在論文的最後，我們將列出並討論系統模擬的結果。 The Service Specific Connection Oriented Protocol (SSCOP) is a new B-ISDN ATM Adaptation Layer (AAL) protocol standard embodying several design principles for high speed link and transport layer protocols. Although SSCOP is now used in the Signaling ATM Adaptation Layer (SAAL), it can also be used in end-to-end user data transfer. However, the flow control algorithm of SSCOP has not been defined in the specification. In this thesis, we propose a rate-based flow control approach for use in SSCOP, named RB-SSCOP, that provides an end-to-end reliable data transfer over UBR service in ATM networks. The design goal of the flow control approach is to achieve a stable, fairness and high-throughput performance by maintaining the bottleneck queue occupancy at a predefined level. We derived the control rules through the analyses of SSCOP operations. Besides, two basic mechanisms, Bottleneck Rate Probing (BRP) and Bottleneck Queue Occupancy Estimation (BQOE) mechanisms, used in the control rules are also proposed. The purpose of BRP mechanism is to probe the service rate and BQOE is used to estimate the per-vc queue occupancy, both at the bottleneck switch. At last, the simulation results of BRP, BQOE and RB- SSCOP are presented and discussed.