Proper interface definition is critical in systems engineering, and when improperly done can lead to protracted integration periods and even loss of property and life. Systems engineers have adopted the ICD (Interface Control Document) as the mechanism for defining and sharing this property of system development. This presentation describes the definition of signal characteristics as SysML constraints on data flows and demonstrates how the Whitebox ICD Table diagram built into MagicDraw can be leveraged to create hardware-to-hardware ICDs (MS Word documents) that include link impairments. Additionally, the presentation also explains how those same constraints can be used to model link budgets.