ative based on TDM, and the testing is relatively straightforward. The benefit of SyncE is that it is a broadly supported technology, is widely deployed, and performs very well. There might be a few unexpected results with early implementations of the newer eSyncE (as with all new technology), but testing SyncE almost never shows unanticipated results. One additional point when testing eSyncE is that frequency testers that are even a couple of years old may not have the accuracy to precisely measure the new generations of eEEC clocks. Figure 12-18 illustrates the method to test the performance of SyncE clocks. Frequency Accuracy Other Tests Tester Tester 10 MHz input PRC/PRS input PRC/PRS Synthetic noise injected into the reference signal SyncE SyncE output input SyncE signal signal output signal NO input reference Freerun clock Locked clock 10 MHz SyncE Figure 12-18 Testing SyncE and eSyncE Equipment Clocks The testing for SyncE, much like testing the TDM technologies, also reflects the differences between SDH and SONET. For the North American markets, the SyncE for any network equipment should be configured as an option 2 EEC clock, and for other markets, it is usually option 1 (ITU- T). Some test cases differ in method and results depending on the option of SyncE being used. It makes sense that an individual operator will only test the option they intend to deploy. There is little point in performing option 1 tests when rolling out option 2 SyncE in North America. The following represents the performance metrics of a SyncE clock from G.8262 (EEC) and G.8262.1 (eEEC): Frequency accuracy: Confirms that when running free, the clock's oscillator (driving the SyncE test signal) is accurate to within 4.6 ppm of the nominal frequency (of the Ethernet sig- nal). The tester measures the output of the standalone DUT (without any reference inputs) to calculate the frequency offset and confirm it is within specification. The length of time for the test is not specified, but for eEEC clocks, very long periods have been pro