Users, devices, and network interfaces have label ranges. The upper bound of the range is effectively the clearance. If the upper bound of the range and the lower bound of the range are equal, the range is a single label.
Clearance label APIs can be used to do the following:
Find the greatest lower bound or the least upper bound between two labels
Compare labels for dominance and equality
Convert clearances between the internal format and the hexadecimal format
For a description of these APIs, see Chapter 2, Labels and Clearances.