One-way frame delay measurements are becoming increasing important for metro networks, especially for applications such as mobile backhaul. These one-way frame delay measurements require accurate time of day (ToD) at each end of the measurement. Today, IEEE 1588v2 PTP provides an efficient and economical means of distributing ToD. However, 1588v2 assumes physical symmetry in the packet network that delivers the timing packet. My paper published at Ethernet Academy explores this topic in detail, and this blog provides a brief synopsis of the paper.