An SDN oriented loop detection mechanism based on TTL statistics

The rise of the network has injected new impetus into the development of traditional networks. Due to the complexity of the network itself and its network programmability, there is a risk of routing loops occurring in the SDN network. This paper proposes a loop detection mechanism. According to the Time To Live (TTL) value of the loop packet, there is approximately periodicity in the same loop. We use sFlow to count the number of packets corresponding to each TTL value of a switch in the loop over a period of time, and perform discrete Fourier transform on the obtained finite-length sequence to observe its frequency domain performance and determine whether there are periodic features. By doing so, it is determined whether there is a routing loop, and the purpose of passively detecting the routing loop is achieved. Compared to existing algorithms, it has advantages in real-time, scalability and false positive rate. The experimental results show that the routing loop detection algorithm based on TTL statistics in this paper still maintains high judgment accuracy under the scenarios of lower stream sampling rate and smaller detection period.