Abstract: In the SDN architecture,the controller has to master the operating state of network data transmission path segment,which is quite significant for controller to implement the network security monitoring and traffic load balancing.Based on the characteristics of SDN architecture,the paper proposed an approach which combines reactive mea-surement and passive measurement for monitoring the network path segment abnormity.The method analyzes the opera-ting state of network traversing path from two aspects of path’s latency and available bandwidth,which can also perform the detection and give an alarm for the abnormal network path segments.Our experiments show that the method can not only measure the latency and available bandwidth of path segment,but also can detect the abnormal path segment out timely and send out alarm signals.In network conditions of constant and variable network cross traffic,the approach can monitor the abnormal path segment and measure the path’s performance parameters efficiently.

Key words: SDN,Latency measurement,Available bandwidth measurement,Path abnormity monitoring