一種非同步傳輸網路之呼叫允入控制

Abstract

在此篇論文中， 吾人提出一種新的呼叫允入控制設計，根據此項設計 間 平均服務品質要求，亦可滿足瞬間服務品質。首先，根 狡犮X長時間平均 封包遺失率，此分析主要研究叢集層流量 (bursty layer traffic) 對封 包遺失率的影響。琱W述模型分析系統的滿載 (overload) 與低載 (underload) 長度， 疑鰜Y，藉由限制封包遺失率可使系統的低載長 度滿足最低 u暫大量的封包遺失對整體服務品質的影響。接著吾人亦以 籅滌妧A行為，並據此導出瞬間封包遺失率，而且將此運用於呼叫允入控 制，以滿足瞬間服務品質。此外， 吾人將呼叫允入控制程序設計成兩個 子程序，並分別以線上估計法 (on-line evaluation) 與查表法 (table look-up) 設計之。 膠’X併前次結果與新呼叫的流量參數算出封包遺 失率。查 しP網路目前狀態決定系統是否處於壅塞狀態。整個設計只 t率 與平均位元速率兩項參數，而且設計簡單並可達到即時運作，所以非常適 合應用於 ATM 網路中。 This thesis proposes a new CAC scheme for ATM networks based on both long-term time averaged and instantaneous cell probabilities for global and individual bursty traffic The long-term time averaged cell loss probability is defined on a logically bufferless fluid flow traffic model. This investigates mainly the relation between bursty layer traffic cell loss probability. The overload period and underload period aggregated traffic are also discussed. Based on the model, relation between the average length of an underload period global cell loss probability is derived. The average length of underload period can also be used as a criterion for admission control because it is equivalent to global cell probability. In addition to long-term time averaged cell probability, we also analyze the instantaneous cell probability, considering the dynamic nature of the traffic, when a network is subject to an admission control. The proposed CAC procedure is divided into two sub-procedures. One called Preliminary CAC (PCAC) procedure designed based on long-term time averaged quality, another Advanced CAC (ACAC) procedure is designed based on quality. An on-line evaluation method is used to implement PCAC procedure, and a table look-up method is used to the ACAC procedure for real-time operation. The operation of proposed CAC scheme requires only two traffic parameters: peak and mean rates. The most important advantage the proposed procedure is that it can be performed in real time.