本标准适用于第1层专用数字服务，其特点是建立了传输路径（即无访问或分离功能）。因此，本标准仅定义了与信息传输阶段相关的性能参数。本标准提供了专用数字通信服务的用户、供应商和供应商所需的性能参数和测量方法列表，以描述这些服务的用户可观察性能（即，本标准未说明错误原因）。它还提供了一个用于达到性能阈值的公式，该公式将指示可用状态和不可用状态之间的转换。给定的服务将只引用那些适用于该服务的参数或阈值。 网络特定参数用于性能分配和网络控制。最终用户可以使用本标准中的概念来衡量最终用户对最终用户的性能和可用性。以前称为T1。503-2002（R2006）。

This standard applies to Layer 1, dedicated digital services, which are characterized by established transmission paths (i.e., no access or disengagement functions). Therefore, this standard defines performance parameters relevant to the information transfer phase only. This standard provides a list of the performance parameters and measurement methods needed by users, vendors, and providers of dedicated digital communications services, to characterize the user-observable performance of these services (i.e., it does not address the causes of errors). It also provides a formula for arriving at the thresholds of performance that will indicate the transitions between the available and unavailable states. A given service will only reference those parameters or thresholds that are applicable to that service. The network-specific parameters are for performance allocation and network control. End users may use the concepts in this standard to measure end-user-to-end-user performance and availability. Formerly known as T1.503-2002(R2006).