 Testing the Hypothesis. We made a statement, now we must back it up with tests. One test I like is correlation. Are the fades on the microwave correlated with the fade occurrences? That test can be done quite easily. If they are correlated, we have some very strong backup that the problem is with the microwave. The frame relay problem may be another matter. First, we could check the FECN and BECN bits to see if there was a change of state passing Node B. If there is no change, assuming that flow control is implemented, then congestion may not be the problem. Removing the frame relay from the system and carrying out a BERT (bit error rate test) over some period of time would prove or disprove the noise problem. A network analyzer is certainly an excellent tool in assisting in the localization of faults. Some analyzers have pre-programmed tests that can save the troubleshooter time and effort. Many networks today have some sort of network monitoring equipment incor- porated. This equipment may be used in lieu of or in conjunction with network analyzers. Again we stress the importance of separating cause and effects. Many times, network analyzers or network management monitors and testers will only show effects. The root cause may not show at all and must be inferred, or separate tests must be carried out to pinpoint the cause. NETWORK MANAGEMENT We might digress here to talk about what is often called tonterías in Spanish. This refers to "silly things." Such tonterías are often brought about by careless installation or careless follow-up repair. Coaxial cable connectors are some of my favorites. Look for intermittents and cold solder joints. A good tool, but not necessarily foolproof, is a time-domain reflectometer (TDR). It can spot where a break in a conductor is down to a few feet or less. It can do the same for an intermittent, when in the fault state. In fact, intermittents can prove to be a nightmare to locate. An electrically noisy environment can also be very troublesome. 21.4.1.4 Conclusions. A conclusion