  We propose an effect called information constraint which is characterized by
the existence of different decay rates of signal strengths propagating along
opposite directions. It is an intrinsic property of a type of open quantum
system, which does not rely on boundary conditions. We define the value of
information constraint ($I_C$) as the ratio of different decay rates and derive
the analytical representation of $I_C$ for general quadratic Lindbladian
systems. Based on information constraint, we can provide a simple and elegant
explanation of chiral and helical damping, and get the local maximum points of
relative particle number for the periodical boundary system, consistent with
numerical calculations. Inspired by information constraint, we propose and
prove the correspondence between edge modes and damping modes. A new damping
mode called Dirac damping is constructed, and chiral/helical damping can be
regarded as a special case of Dirac damping.
