This bitmap integer reports which SONET/SDH Section-layer defects are currently active, with each bit position representing a distinct defect (e.g., bit 2 for Loss of Signal) and the sum of set bits forming the reported value; sonetSectionNoDefect is set only when no other defect bit is set. An admin cares because a nonzero, non-'no-defect' value here means the section layer itself has a live physical-layer problem (like LOS) that will cascade into failures at every higher layer (line, path) on this interface. For example, a value with bit 2 set indicates Loss Of Signal is currently active on this section, which explains why every downstream path on the same interface is also failing.