在階層式多網域SDN控制器架構下實現權重式路由

Abstract

在本篇文章中利用多控制器架構來減輕單一控制器的負擔，依據服務應用的全域性與區域性特性設計出階層式控制器架構，設計出控制器間的溝通機制，利用cache減少控制器間溝通的消耗，最後實作並改良路由演算法，並利用網路流量為權重值以避免網路壅塞的產生。隨著軟體定義網路（Software Defined Network）的發展，我們可以藉由集中式控制器來管理網路上各式各樣的活動行為，但以目前網路上的活動量，在一個中央控制器的架構下將無法滿足如此大量的服務應用需求，因此我們利用多控制器架構來分擔單一控制器的負擔。此外，服務應用可被區分為區域型應用與全域型應用兩大類，不需要有整體網路資訊的為區域性應用，由區域性控制器（local controller）所管理；而需要整體網路資訊的為全域性應用，由全域性控制器（global controller）所管理，依據服務應用的區域性與全域性區別，我們設計了階層式控制器架構（hierarchical controller）。在此架構下，除了減輕單一控制器的負擔，使得服務應用的管理劃分更加有效率，控制器間的溝通便是一個重要的問題。控制器間的溝通提供了更新控制器資訊和控制器訊息傳遞的管道，但也造成了頻寬消耗和訊息延遲，我們藉由cache機制在區域性控制器儲存全域性資訊，減少了頻寬消耗和訊息延遲的問題；而在路由方面也加進了考量網路現有流量的權重值（weight），藉此權重值來選擇流量最小的路徑，以避免網路壅塞。最後我們使用Mininet和Cbench測試並評估我們所設計的架構之效能，證實了階層式多網域SDN控制器架構可大幅度的分散一個控制器的負擔，增進整個控制器架構了吞吐量，而在權重式路由方面也增加了整體網路頻寬的使用率。

The multi-controller architecture is used in this paper to relieve burden on single controller. Based on the global and local property of service application, we first design the hierarchical controller architecture and the communication mechanism between controllers. Then, we propose to use cache to reduce communication overhead between controllers. Lastly, the system was implemented, and the routing algorithm is improved using network traffic as weight to prevent network congestion. By software-defined network (SDN), we can manage all kinds of network activities with centralized controllers. However, for the amount of activity on the current network, the architecture with only one central controller cannot satisfy so many requests from various service applications. Therefore, we use multi-controller architecture to share the heavy burden of the single controller. In addition, service applications can be divided into two types: local applications and global applications. Applications that need not the whole network information are called local applications, which are managed by local controllers. Global applications need the whole network information and are managed by global controllers. Based on the different properties between local and global service applications, we design a hierarchical controller architecture. In this architecture, not only lightening the burden of single controller was an issue, but also the communication between controllers was an important problem. A method for updated controller information and a channel of message delivering were provided because of the communication between controllers, but it also caused the bandwidth consumption and message delays. We propose the use of high-speed cache to hold the global information in the local controller, we reduced the problem of the bandwidth consumption and message delays. In terms of routing methods, we used the weight value considering the existing network traffic to choose the path with least traffic to prevent network congestion. Finally, we use mininet and cbench to test and evaluate the efficacy of our architecture. We verified that hierarchical multi-domain SDN controller-architecture could considerably distribute a controller’s burden and increase the throughput of whole controller architecture. In terms of weighted routing, the whole network bandwidth usage ratio was also increased.