D同步傳輸模示網路中ABR服務之有效訊務控制方法

Abstract

非同步傳輸模式網路在單一環境中提供大量頻寬且支援不同服務品質之需 求。但是﹐現存傳統的一些資料應用無法預知滿足其需求的頻寬。因此﹐ 這類資料應用需要一種新的服務﹐可以依據目前網路的實際狀態動態地調 節傳輸速率﹐且與其它使用者公平的分享網路資源。這類的網路服務稱為 best-effort 或 available-bit-rate (ABR)。 由於訊務往往是無 法預知且是突發的﹐因此ABR服務比其它的訊務服務更富挑戰性。對於ABR 訊務控制方法﹐它需要提供每一使用者有效且動態地分享可用的頻寬。根 據網路的實際狀態與ABR訊務﹐動態地調整實際的傳輸速率。 論文裡我們提出新的ABR訊務控制方法﹐這個方法包含了End-to-End Rate-based控制和Link-by-Link Feedback控制。這新的Rate-based控制 可以動態調整來源訊務的傳輸速率﹐且在使用者相互競爭之間維持真正的 公平分享網路資源。利用以回饋控制為基礎的緩衝區設計﹐達到避免訊務 間之Head-of-Line (HOL) blocking。最後，藉由實驗之模擬結果顯示﹐ 我們提出的解決方法可以達到沒有資料的遺失、最大網路資源之使用、和 公平地分享網路資源 Asynchronous transfer mode (ATM) networks provide large bandwidth and supportdiverse traffic characteristics as well as multiple quality of services (QoS)requirements in a single integrated environment. These different types of traffic are statistically multiplexed to efficiently utilize the network bandwidth. However, most of the data networking applications can not predict their ownbandwidth requirements, such data applications usually require a service thatdynamically shared the available bandwidthamong all active connections and isreferred to as a best-effort service or available-bit-rate (ABR). Since the traffic is usually bursty and unpredictable, the traffic control for ABR service poses more challenge than other services. The ABR traffic control mechanism is required to provide an efficient statistical sharing of available bandwidthamong all active connections. The actual transmission rate of ABR traffic must be dynamically regulated according to the network statistical information toimprovethe bandwidth utilization. This paper presents an ABR traffic control approach which combines a new end-to-end rate control with link-by-link feedback control. The new rate control can regulate the transmission rate of source traffic dynamically and keep the real fairness among all active connections. Abuffering scheme based on feedback control that avoids Head-of-Line (HOL) blocking for the best-effort (ABR) traffic is used. The simulation results show that the proposed ABR traffic control can achieve cell-loss-free, maximum link utilization, and fairness.