本标准描述了一个指标，该指标量化了底层网元中断对IP服务可用性的影响。目前，网络管理系统（NMS）工具提供的收集必要数据以估计这种影响的能力有限。该指标的目的是鼓励设备供应商开发大修测量能力/技术，以进行指标估计。

This standard describes a metric that quantifies the impact on IP service availability due to an underlying network element outage. Currently, Network Management System (NMS) tools offer limited capabilities to collect necessary data for estimating this impact. The purpose of this metric is to encourage development of outage measurement capabilities/techniques for metric estimation by equipment vendors.