SNTP time synchronization accuracy measurements

Time synchronization is a key requirement in many automation systems. There are currently two predominant technologies for time synchronization in automation systems: SNTP (Simple Network Time Protocol) and PTP (Precision Time Protocol). PTP is the preferred technology and has several advantages over SNTP including far better accuracy in most if not all situations. However, legacy systems in many situations have to rely on SNTP. This is a challenge since the requirements on accuracy increase while the systems become larger and more complex. Thus, it is of interest to investigate what kind of accuracy level can be expected with the use of SNTP in modern switched networks. This paper shows that accuracies at the milliseconds level can be achieved for small networks. It is also analyzed how the network infrastructure and the end nodes contribute to the measured inaccuracy.