对于用户和业务提供者，网络生存性变得越来越重要。生存性是设计和规划新的电信网（如ＳＤＨ网和ＡＴＭ网）面临的一个根本的、亟待解决的问题。在过去的几年中，已提出几种应用于ＳＤＨ和ＡＴＭ网络中的不同的恢复机制。但在比较和评价恢复机制的性能时，以往只采用一种简单的方法。为克服该方法的缺陷，本文提出了面向用户和面向网络工程师的恢复机制可用性的定义。在后者的可用性分析中，考虑网络生存性对空闲容量的要求。由于一个网络的状态空间很大，进行可用性精确分析是不可行的，本文建议采用ＯＲＤＥＲ算法来近似测量可用性。同时还给出了恢复机制可用性定义的应用。一个应用是：网络工程师利用可用性定义，设计一个具有成本有效性的生存网络。另一个应用是：在ＡＴＭ生存网络的ＣＡＣ协商参数中，增加了一组新的参数—生存性性能参数。最后在计算机模拟中验证了：在评价恢复机制性能时，两个可用性的定义比传统方法更有效和更有意义 Network survivability becomes more and more important to users and service providers. Survivability is a fundamental and pressing issue in the design and planning of new telecommunications networks such as the SDH network and the ATM network. In the past few years, several different recovery mechanisms have been proposed for use in SDH and ATM networks. However, in the past, only a simple method was used to compare and evaluate the performance of recovery mechanisms. In order to overcome the shortcomings of this method, this paper proposes the definition of availability of recovery mechanisms for users and network engineers. In the latter usability analysis, we consider the requirement of network survivability for free capacity. Due to the large state space of a network, it is infeasible to make an accurate usability analysis. This paper proposes an ORDER algorithm to approximate the measurement availability. At the same time, the definition of availability of recovery mechanism is also given. One application is that network engineers use usability definitions to design a cost-effective survivable network. Another application is that a new set of parameters, survivability parameters, is added to the CAC negotiation parameters of the ATM surviving network. Finally, it is verified in computer simulation that the definition of two usability is more effective and meaningful than the traditional method in evaluating the performance of recovery mechanism