運用單調傳輸率排程法則與單調期限排程法則作訊務管理

Abstract

對於提供服務品質保證的網路來說，訊務管理是很重要的工作。為了使網 路有限的資源使用最佳化，同時兼顧到使用者要求的服務品質，網路資原 必須完全根據訊務源精確的特性賦予來配置。在單一處理器中，參考文獻 [1]中提出的單調傳輸率排程法則是最佳化的固定優先權分派法則。緊接 著，單調期限排程法則在參考文獻[12]中提出，單調期限排程法則是單調 傳輸率排程法則的一般形式，並更適用於即時網路。使用這兩種排成法則 作訊務排程的先決條件是所有訊務源必須週期性的產生訊息。在論文中， 吾人使用單調傳輸率排程法則及單調期限排程法則對於常數位元傳輸率的 連線作網路資源的配置，並且找出這些連現可單調傳輸率排程和可單調期 限排程的充分必要條件。根據這些條件，吾人設計允入控制法則並加以硬 體實現來加快允入控制的速度。值得注意的是多媒體通訊的應用上並非全 都是常數位元傳輸率的應用，而且常數位元傳輸率的訊務源在多級網路下 幾乎沒辦法維持其常數位元傳輸的特性。吾人最後在非同步傳輸模式網路 的環境下設計一排程器，以解決此問題並排程可單調傳輸排程或可單調期 限排程的訊務。 Traffic management is important for networks which guaranteequality of service. To optimize utilization of limited resourceand meet quality of service requirements simultaneously, traffic sourcesshould be characterized accurately and resource should be allocatedprecisely based on the characterization of traffic source.The rate monotonic scheduling algorithm (RMSA) proposed in [1] is the optimal fixedpriority assignment scheme on a single processor. Successively, the deadline monotonic schedulingalgorithm (DMSA) is proposed in [12]. The DMSA is a generalized version of the RMSAand is more adaptive for real- time networks. To use any of these two algorithms toschedule traffic, sources should generate messages periodically.In this thesis, we use both RMSA and DMSA to allocate resource to constantbit rate (CBR) channels in real-time networks. We determine the necessary and sufficientconditions for a set of channels to be rate monotonic and deadline monotonic schedulable.According to the necessary and sufficient conditions, we also design fastadmission control algorithms with potential hardware implementations.Note that the applications in multimedia communications are not always CBR applicationsand the traffic generated by CBR sources almost cannotmaintain their CBR property in multihop networks. A scheduler that resolve thisproblem and schedule the traffic generated by rate monotonic or deadlinemonotonic schedulable channels for ATM networks is designed in this thesis.