This read-only Integer32 reports the number of SONET Line-layer Byte Interleaved Parity errors detected on this OC-3 port during the current 15-minute period. It gives an administrator a line-layer signal-quality indicator distinct from the section-layer BIP counter, helping isolate which SONET layer is experiencing degradation. For example, an operator seeing line-layer errors rise while section-layer errors stay flat would suspect a problem further along the optical path rather than at the immediate local connection.