The first PTP Protocol defined for time and phase transfer in telecom, G.8275.1, requires that all network switches and routers act as Boundary Clocks with respect to PTP.  This allows for network architects to estimate the accumulated time transfer error in the network path between the Grandmaster clock and the radio heads that need time synchronization from the Boundary Clock performance specifications.  Recognizing that many telecom networks would not immediately upgrade all switches and routers to support PTP, G.8275.2, Precision time protocol telecom profile for phase/time synchronization with partial timing support from the network, was also defined.  Here the presence of packet delay variation (PDV) is expected due to variable queueing delays in switches and routers that do not support PTP.  Such PDV is known to result in time transfer errors that are statistically non-Gaussian, typically exhibiting skewed error distributions with long tails in the distribution and non-stationary properties. Standard PLLs such as PI filters or Kalman filters are based on averaging to remove noise. However, such methods perform poorly when noise is skewed or with long tails in the distribution, and the non-stationary results in no static mean value to stabilize on.  Even robust statistics like the Allan Deviation do not always converge as more data points are added when there are long tails in the distribution. To manage PDV, PTP time receivers implement nonlinear PLLs that use prefiltering—commonly referred to as lucky packet filters—to select received timestamps, forwarding only packets with minimal delay for averaging.    More complex variations of lucky packet filters are also in use, but the idea is always to pick the Sync messages and Delay Request messages with the least PDV. Another problem with large networks using G.8275.2 is changes to PTP message latencies resulting from traffic engineering mechanisms.  This can result in two problems: PLL transients due to step changes in the network delay Large PTP errors due to asymmetry when the Sync and Delay Request messages take different routes through the networks, In this presentation we present: An analysis of the limitations of the lucky packet filters A description of network properties where partial timing support PTP will work well Additional capabilities that are required to overcome partial timing support challenges in larger networks Enter description here.