This value gives the starting label of a waveband Generalized Label's wavelength range, valid only when gmplsLabelSubtype is wavebandLabel(6). An engineer uses it along with gmplsWavebandEndLabel to define the lower boundary of the contiguous wavelength range that makes up a waveband. For example, a gmplsWavebandStartLabel of 10 combined with an end label of 20 would define a waveband spanning wavelength labels 10 through 20.