Definitions of restoration mechanism availability and their applications

Network/service survivability is an important problem demanding prompt solution in the design and planning of new telecommunications networks (e.g., SDH networks and ATM networks). Different restoration mechanisms for SDH and ATM networks have already been developed. The previous literature comparing and evaluating the restoration mechanisms only uses a simple method. In order to overcome the shortcomings in the traditional method, this paper proposes the customer-oriented and network engineer-oriented definitions of restoration mechanism availability. In the second definition, the extra spare capacity requirement in the network is taken into account in the availability analysis. Because an exact measurement of the availability is not feasible due to the large number of failure states in the network, an ORDER algorithm (Li and Silverter 1984) to get a reasonable subset to approximately measure the availability is recommended. Then, applications of the definitions are given. One application is how this definition is used by network planner/engineer to construct a cost-effective survivable network. Another application is that a new group of parameters-survivability quality of service (SQoS) is defined and added to CAC (connection admission control) of the ATM survivable network. Finally, a simulation using two definitions is performed. The simulation results prove that two availabilities can evaluate restoration mechanisms more sufficiently and more meaningfully