Self-Monitoring SDN Switch Network Measurement

軟體定義網路使網路能夠程式化。擁有全域觀的中央控制器能透根據網路的狀態來動態調整任何一個交換器內的轉遞規則。現存的監控方式皆使用網路流的狀態搭配網路架構和網路流的路徑來計算網路內各個連結的使用量。網路的流量變化非常劇烈，為了能更快速地做出對應，部分研究使用傳輸控制協定內的序列號來計算網路流的速度和使用埠映射同步來降低處理時間。然而，並非網路協定內序列號等價於網路流所傳送的位元數而埠映射同步產生過多額外的流量。 在這個研究中，我們提出使用埠計數器和OpenFlow內的狀態要求訊息和狀態回復訊息的兩階段式的網路偵測。我們讓交換器使用埠計數器計算連接上交換器的連結使用量，並將結果傳送給中央控制器。根據網路內各個連結的使用量，中央控制器判斷壅塞的連結傳送狀態要求訊息來獲取網路流的資料來進行轉遞規則的變動。Software-defined networking architecture with OpenFlow makes network programmable that centralized controller can decide forwarding rule in every switch dynamically according to network status. Existing measurements gather flow-level information, and using topology and flow path to construct link utilization table. To react rapidly to network changing, some works use TCP sequence numbers to quickly calculate flow rate and leverage port mirroring to decrease latency. However, not all protocol has sequence numbers as byte counter of the flow, and port mirroring cause large overhead. In this paper, we present a two-tier measurement architecture that uses both port counter and OpenFlow StatsReq (request) and StatsRes (response) message to extract global view of the network. We let switch use port counter to monitor itself, and send the link state message to the controller. Based on the link utilization table, updated by switch message, the controller finds the congested link and queries flows information to change forwarding behavior