Method for evaluating the stability of communication over a telecommunication line, the method comprising - ascertaining physical line data characterizing a physical characteristic (CV, ES, SES; Resync, FI) of each line of a fist set of subscriber lines including the telecommunication line; - collecting service quality information describing a quality of a service provided over each line of a second set of subscriber lines and perceived by end users of said line as satisfactory or unsatisfactory; - associating the service quality information related to at least one particular line with the physical line data related to the same particular line; and - determining (63, 65) at least one threshold (Θ u, Θ s, Γ u, Γ s) for deciding to which stability class (S, R, U) of a plurality of stability classes (S, R, U) the digital subscriber line belongs; characterized in that the method comprises - calculating the at least one threshold (Θ u, Θ s, Γ u, Γ s) for a stability metric (MTBE; MTBR) of the line, the at least one threshold (Θ u, Θ s, Γ u, Γ s) depending on the physicalline data with associated service quality information and the stability metric depending on multiple physical characteristics (CV, ES, SES, Resync, FI) of the line; and defining said at least one threshold as anyone of an intersection point of the distributions representing said stability metrics (MTBE, MTBR) for satisfactory and unsatisfactory lines or as a percentile of the distribution representing said stability metrics (MTBE, MTBR) for unsatisfactory lines; and - adapting a calculation rule (w opt, s opt) for calculating the stability metric (MTBE, MTBR) such that a discriminant measure of the stability metric related to the service quality information is optimized, wherein said calculation rule includes a linear combination of said multiple physical characteristics (CV, ES, SES; Resync, FI) and said adapting the calculation rule includes computing weight coefficients (w opt, s opt) for said linear combination such that said deciding is optinlized. - ascertaining physical line data characterizing a physical characteristic (CV, ES, SES; Resync, FI) of each line of a fist set of subscriber lines including the telecommunication line; - collecting service quality information describing a quality of a service provided over each line of a second set of subscriber lines and perceived by end users of said line as satisfactory or unsatisfactory; - associating the service quality information related to at least one particular line with the physical line data related to the same particular line; and - determining (63, 65) at least one threshold (Θ u, Θ s, Γ u, Γ s) for deciding to which stability class (S, R, U) of a plurality of stability classes (S, R, U) the digital subscriber line belongs; - calculating the at least one threshold (Θ u, Θ s, Γ u, Γ s) for a stability metric (MTBE; MTBR) of the line, the at least one threshold (Θ u, Θ s, Γ u, Γ s) depending on the physicalline data with associated service quality information and the stability metric depending on multiple physical characteristics (CV, ES, SES, Resync, FI) of the line; and defining said at least one threshold as anyone of an intersection point of the distributions representing said stability metrics (MTBE, MTBR) for satisfactory and unsatisfactory lines or as a percentile of the distribution representing said stability metrics (MTBE, MTBR) for unsatisfactory lines; and - adapting a calculation rule (w opt, s opt) for calculating the stability metric (MTBE, MTBR) such that a discriminant measure of the stability metric related to the service quality information is optimized, wherein said calculation rule includes a linear combination of said multiple physical characteristics (CV, ES, SES; Resync, FI) and said adapting the calculation rule includes computing weight coefficients (w opt, s opt) for said linear combination such that said deciding is optinlized.