g the control-plane aspects of the solution. Network limits and solution requirements outline the end-to-end performance and require- ments that need to be met across the complete timing distribution network. These documents define the expected quality of the timing signal that emerges from the end of the timing chain and are extensively modelled by sophisticated mathematical simulations. Equipment clock specifications and limits define the performance and functional require- ments that each component of the end-to-end timing distribution needs to meet, SO that the net- work limits will not be breached. This includes many recommendations that define the specific- ations and performance for reference clocks such as a PRTC. Telecom profiles define the protocol, message flows, fields, and values as well as the clock se- lection mechanisms that will run on the previously defined clocks. These profiles define the ex- act mechanism and messages used to transfer frequency, phase, and time. Other documents and recommendations exist that may be harder to characterize, such as those defining the electrical specifications of a timing interface (such as a 10-MHz signal) or the method used to carry quality-level traceability in the network (such as ESMC). There may also be documents concerning some related area of interest to the scenario or an operational as- pect such as OAM. Table 8-3 puts the Q13/15 recommendations into context within these categories, grouping them via the method of time transfer. You should understand that it is not necessary to try and understand all these recommendations, or even a significant subset. So, don't lose hope if it seems somewhat over- whelming at this point. Table 8-3 TDM Versus Packet-Based Synchronization Methods TDM and Physical Requirements Packet Network Network Functional architecture G.810 G.8260, G.8265, G.8273, G.8275 Synchronization layer G.781, G.707 (SSM) G.8264 (ESMC), G.781.1 functions Network limits and solution G.8261, G.8261.1, G.8271, G.823, G.824, G.825 requirements G.8