cational material on the topic available if you know where to find it (several pointers are provided in the "Further Reading" section at the end of the chapter). The problem is that many publicly available educational resources on the topic assume that you know what you are doing before you start testing. The authors frequently deal with customers and prospective customers who have gotten themselves into difficulties by misapplying a test case to the wrong topology or judging the result using the wrong specification or metric. Most times, a quick phone call will uncover the mistake, and the tester can move on with their equipment certification. The authors have seen numerous major test efforts where the results indicate that the equipment un- der test has failed one or more test cases. In many of those circumstances, either the test cases were wrongly executed or the result was compared against the wrong pass/fail criteria. For example, there are two broad categories of testing: end-to-end network testing and standalone clock testing. The topology, test cases, and expected result are different for each case. So, this section will lead you through the fundaments of timing testing and point out the common mistakes that are very easy to make. First, Figure 12-7 should remind you of the most relevant ITU- T recommendations that provide a basis for conformance testing. Timing characteristics (packet-based recommendations) Frequency Phase & time ITU-T G.826x ITU-T G.827x G.8261 G.8271 G.8261.1 G.8271.1 (FTS) Network (Mobile BH limits) limits G.8271.2 (PTS) G.8262 (EEC) G.8272 (PRTC + T-GM) G.8262.1 (eEEC) G.8272.1 (ePRTC) Clock node G.8273 specifications G.8263 (Framework) (Packet slave clock) G.8273.2 (T-BC/T-TSC) G.8266 (Packet master clock) G.8273.3 (T-TC) G.8273.4 (PTS) G.8265 G.8275 Requirements (PTP requirements) (PTP requirements) G.8265.1 G.8275.1 profiles (PTP profile) (PTP profile FTS) G.8275.2 (PTP profile PTS) Figure 12-7 ITU-T Recommendations Just about all the test cases and performance requirements are c