This Recommendation outlines minimum requirements for the timing functions of the packet slave clocks as defined in [ITU-T G.8265]. It supports frequency synchronization distribution when using packet-based methods. This Recommendation allows for proper network operation when a packet slave clock is timed from a packet master clock as defined in [ITU-T G.8265]. This Recommendation focuses on mobile applications@ and in particular on the delivery of frequency synchronization for end applications@ such as mobile base stations. It supports the architecture defined in [ITU-T G.8265]. Other applications are for further study. This Recommendation focuses on two different deployment cases for the packet slave clock as follows. ?C Packet slave clock embedded in a device co-located with the end application@ as shown after the connection C1 in Figure 3 of [ITU-T G.8261.1]. ?C Packet slave clock embedded within the end application@ as shown after the connection C2 in Figure 3 of [ITU-T G.8261.1]. This second case is for further study for the first version of this Recommendation. Other deployment cases for the packet slave clock are for further study. This Recommendation focuses on the types of networks corresponding to the hypothetical reference models@ HRM-1 and HRM-2@ defined in [ITU-T G.8261.1]. NOTE ?C For long observation intervals@ the packet-based equipment clock ?C slave ?C frequency (PEC-S-F) is expected to compensate for temperature variation effects; therefore@ the output of the PEC-S-F will converge to the 1 ppb slope. The HRM-2 type of network is for further study for the first version of this Recommendation. Other types of networks are outside the scope of this Recommendation. This Recommendation defines the minimum requirements for the packet slave clocks. These requirements apply under the normal environmental conditions specified for the equipment. This Recommendation includes clock accuracy@ packet delay variation (PDV) noise tolerance@ holdover performance and noise generation. The start-up conditions (e.g.@ variable filtering bandwidth at start-up and stabilization period) are for further study.