在SDN網路下滿足服務品質之適應式路由機制

Abstract

於傳統網路上，由於缺乏對於整體網路資源的掌握，所以難以針對多媒體應用程式，如視訊串流，提供服務品質(QoS)保證的服務。 軟體定義網路提供了一個創新的方法，利用將控制層與轉送層分開來實現集中控制與管理工作。在本論文中，我們提出一個在軟體定義網路上，對於視訊串流提供服務品質保證的動態路由方法。透過可適性編碼視訊 (scalable encoded videos)，將其中的基礎層與加強層的封包做分類，並賦予基礎層有重新找路由的最高優先權，使能在最短路徑不符合延遲差異的限制下，重新找路由直到有可用頻寬充足的路徑。相反地，若此路徑可用頻寬不足時，則讓加強層封包重新導路由至此路徑上。實驗結果證明，與OpenQoS相較下，我們提出的方法，對基礎層的封包遺失率(Packet Loss Rate)，可以改善最高達77.3%，並針對最短路徑與可行路由路徑，在不同網路負載情況下，提供至少51.4%的覆蓋率。

For multimedia applications, such as video streaming applications, with the need of Quality of Service (QoS) support, it is difficult to successfully implement QoS architectures in traditional networks which lack a global view of overall network resources. Software Defined Networking (SDN) provides an innovative architecture to realize central management among networks. In this paper, we propose an adaptive routing approach for video streaming with QoS support over SDN networks, called ARVS. In our approach, base layer packets and enhancement layer packets of video bit streams are treated separately as two levels of QoS flows. During video streaming, if the shortest path does not satisfy the delay variation constraint, the base layer packets have the first priority to be rerouted to a calculated feasible path based on available bandwidth of this path, and the enhancement layer packets will stay on the shortest path. However, if there is no available bandwidth in this path, the base layer packets will stay on the shortest path while the enhancement layer packets will be rerouted to this path. Therefore, the video quality would be guaranteed easily due to the congestion of the shortest path has been mitigated. Simulation results have shown that compared with OpenQoS, our approach can reduce up to 77.3% of the packet loss rate for the base layer packets of video bit streams, and also enhance at least 51.4% coverage under various network loads of the shortest path and the feasible path.