像智能電話，傳感器，移動設備等現代智能設備需要更好的同步精度以準確和及時的傳輸和接收數據。較新的時序協議像Precision Time Protocol（PTP）被用來實現更高的精確度。 PTP實現在亞微秒級的同步精度，而且依賴於設備之間的頻繁交流，以實現快速同步。在傳統的網絡環境中，許多數據流的帶寬有限資源的競爭，重或突發的流量可以延長和變化PTP同步訊息的網絡傳輸時間。解決這個問題的好辦法，就是實施Quality of Service（QoS），讓PTP詗息有自己的帶寬片和有較高優先於其他流量的權利。在傳統的網絡服務質量是困難和繁瑣的配置。Software Defined Network（SDN）提供了一個簡單而集中的配置平台來實現的QoS以允許PTP同步流量有一個平滑且一致的網絡傳輸環境。在本論文中，我們研究了SDN的QoS對PTP時間同步協議的效力。在SDN QoS實施將包括兩部分：帶寬分配和優先級隊列。我們將使用一個虛擬平台去設立SDN環境來研究各種背景流量在使用和不使用SDN的QoS的情形下對PTP同步精度的影響。

Modern smart devices like smart phones, sensors, mobile devices requires better synchronization accuracy in order to accurately and timely transfer and receive data. Newer timing protocols like the Precision Time Protocol (PTP) were used to achieve better accuracy. PTP achieves synchronization accuracy at sub-microsecond level, but relies on frequent communication between devices to achieve fast synchronization. In tradition networks where many data flows are competing for limited bandwidth resource, heavy or bursty flows can prolong and vary network transmission time of PTP synchronization messages. A good way to deal with this problem is to implement Quality of Service (QoS) to allow PTP messages to have their own slice of the bandwidth and a higher priority over other traffic flows. QoS in traditional networks is difficult and tedious to configure. Software Defined Network (SDN) provides a simple and centralize configuration platform to implement QoS to allow PTP synchronization traffic a smooth and consistent network transmission environment. In this thesis, we study the effectiveness of SDN QoS on PTP time synchronization protocol. The SDN QoS implementation will include two parts: bandwidth allocation and prioritized queues. We will use a virtual platform to set up a SDN environment to study the effects of various background traffics on the synchronization accuracy of PTP with and without using SDN QoS.

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