The purpose of this standard is to define a comprehensive basis for assessing the performance of Integrated Services Digital Networks (ISDNs) providing telecommunication service in accordance with the American National Standards and ITU-T Recommendations identified herein. This standard: (a) defines parameters that 5 be used to describe the performance of ISDN bearer services and (b) specifies worst-case objectives for the ISDN performance parameters. The parameters and objectives are applicable to circuit mode and packet mode ISDN bearer services. Unless noted otherwise in this standard, the defined parameters and specified objectives apply to ISDN services using a single B channel and/or D channel; planned revision to this standard will address other ISDN bearer services (e.g., n x 64 kbit/s). Practical methods for measuring ISDN parameter values will be specified in a planned supplement to this standard.