This presentation discusses: the need to transport TDM (time-division multiplexed) services over packet switched networks (PSNs); the challenge of recovering a TDM clock at the far end that meets TDM needs; modelling packet delay variations (PDVs); Gaussian and non-Gaussian models; the challenge of meeting synchronisation requirements; and exploiting PDV statistics in order to attain conformant MTIE (maximum time interval error) and TDEV (Time DEViation) wander limits.