非同步傳輸模式網路中虛擬路徑之動態管理

Abstract

ATM網路是期望能夠支援具有不同訊務特性的服務。在ATM網路中﹐一條 虛擬路徑連線包含一條或數條虛擬路徑﹐而這些虛擬路徑是用在簡化網路 的資源管理﹐我們假設具有相類似的訊務特性及服務品質要求的虛擬連線 被統計多工在同一條虛擬路徑。這樣的好處包括了簡化服務控制､增加多 工效益以及提高網路資源的使用率。但是﹐如果分配給虛擬路徑的頻寬大 小是固定的﹐便無法反應訊務的波動。在這種情形下﹐便會發生同一條實 體線路中﹐即使其他的虛擬路徑仍有未使用的資源﹐某一條虛擬路徑仍會 有資源不足卻又不能增加頻寬的現象。在這份論文中﹐我們提出新的資源 管理機制﹐以應用在兩種層級的資源分配。在個別虛擬路徑層級中﹐我們 提出方法以推導出「最少所需頻寬量」（least required bandwidth）。 這個方法只需要簡單的計算。最少所需頻寬量的大小是滿足虛擬路徑中現 有連線的服務品質要求所需的最少頻寬量。在網路層級中﹐我們提出虛擬 路徑間的分散式資源控制方法﹐其中包括了週期性控制以及插斷式的控制 方法。 Asynchronous transfer mode (ATM) networks are expected to support serviceswhich involve diverse traffic characteristics( voice, data, voice, etc□). Inan ATM network, a virtual path connection (VPC) is a labeled path consistingof one or more virtual paths(VPs), which is introduced for simplifying thenetwork resource management. We assume that virtual connections of similartraffic characteristics and QoS requirement are statistically multiplexed ona VP. The advantages include: simplifying in the implementation of servicecontrol, and increasing both multiplexing gain and resource utilization. However, if the assigned resource of each VP is fixed, it cannot absorbtraffic load fluctuation. Under this situation, it is likely to happen thata VP has no remaining resource while other VPs on the same physical linkstill have plenty of free resources. In this thesis, we propose new resourcemanagement mechanisms which can be applied to two levels of resourceallocation. At the individual VP level, we present a mechanism to derive theleast required bandwidth (LRB) whenever a new connection is established or anexisted one is released. The mechanism only needs simple calculation. Theleast required bandwidth is the minimum amount of capacity needed to meet theQoS requirement of virtual connections on a VP. At the network level, adistributed resource control among VPs is presented the control process canbe triggered on a periodical basis, or interrupt basis which occurs when thecall blocking probability in a VP reaches a predefined threshold.