Poor balance resulted in a 1000BASE-T switch operating at 100BASE-TX
If your link certifies with good margin but the owner is still complaining about performance, you may wish to consider a TCL (Transverse Conversion Loss) measurement. The DSX-5000 CableAnalyzer is the only tester capable of this measurement in the field. (Not available on the DTX CableAnalyzer - would require new hardware). For a full list of available videos, click here.