formation (such as external measurement against a reference clock) to understand that cTE is present and potentially correct it. Simply, clock has no built-in mechanism to detect it, SO it has no way to correct or reject it. For the solution to work, a T-BC/T-TSC (especially the last in the chain) must tolerate the max- imum dTE that could accumulate over the complete chain of T-BCs. An MTIE mask is used to spe- cify the dTE, and it is defined based on the network limit specified in G.8271.1. This makes sense because if the last node in the chain (which sees the most dTE) cannot tolerate the accumulated noise as an input, the chain is broken. Figure 9-27 illustrates the dTE network limit that a clock must be able to tolerate, as specified in G.8271.1. 580 ns 280 ns 200 ns 100 ns 10000 Figure 9-27 Dynamic Time Error Network Limit (MTIE) for T-BC/T-TSC-Based on Figure 7- 2 of ITU-T G.8271.1 For frequency, the maximum noise that should be tolerated at the frequency input is described in ITU-T G.8262, G.813, and G.8262.1 (for Class C clocks based on eEEC). Noise Transfer As the name implies, the noise transfer of a clock describes how much of the noise present on the input of a clock gets passed through (transferred) to the output of the clock. This metric is usually expressed in terms of bandwidth because the clock is a filter to the input noise. Bandwidth also describes the filter characteristics applied to the input signals before the recovery of frequency, phase, and time. Refer to the section "Noise Transfer" in Chapter 5 for more details on the noise transfer function of a clock and its impact on the timing network. That chapter extensively covers clock bandwidth in the section "Low-Pass and High-Pass Filters." The characteristics of noise transfer are determined by the numerous timing paths that exist through the clock. These timing paths can transfer time error from the input to output, and each needs to be measured for its contribution to noise transfer. As illustrated in Figure 9-28, for a T-BC/T-TSC, there