and HPF) that can filter out noise based on the clock band- width (refer to the earlier section "Low-Pass and High-Pass Filters"). The main metric used to describe how noise is passed from input to output is clock bandwidth, which was explained in the section "Low-Pass and High-Pass Filters." For example, the noise trans- fer of an Option 1 EEC is described in clause 10.1 of ITU-T G.8262 as follows: "The minimum bandwidth requirement for an EEC is 1 Hz. The maximum bandwidth requirement for an EEC is 10 5.3 Holdover Performance Given an accurate reference clock as an input signal, one can achieve a well-synchronized clock. This is the fundamental principle of timing synchronization whereby a master clock drives the slave clock, always assuming that the master clock itself is stable and accurate. Occasionally, there will be cases where the master clock becomes unavailable. During such periods, the local clock is no longer disciplined by a master (or reference) clock. Most synchronization- based applications need to know the amount of frequency drift that can occur during such events. The time during which a clock does not have a reference clock to synchronize to is called clock hol- dover. In this state, the clock behaves like a flywheel that keeps spinning at a constant speed even when it is not being actively driven, SO this is sometimes also referred to as flywheel mode. And the measure of the speed with which a slave clock drifts away from the reference or master clock is called its holdover performance. The clock's ability to maintain the same frequency over an inter- val of time without a reference frequency being available is called frequency holdover. Similarly, time or phase holdover is the ability to maintain phase accuracy over an interval of time without the external phase reference. This synchronization across network elements is achieved either via a physical signal (such as SyncE) or via precision time protocol (PTP) packets carrying timing synchronization information. There is even the ability to c