Restoration schemes with differentiated reliability

Reliability of data exchange is becoming increasingly important. In addition, applications may require multiple degrees of reliability. The concept of differentiated reliability (DiR) was recently introduced in [A. Fumagalli and M. Tacca, January 2001] to provide multiple degrees of reliability in protection schemes that provision spare resources. With this paper, the authors extend the DiR concept to restoration schemes in which network resources for a disrupted connection along secondary paths are sought upon failure occurrence, i.e., they are not provisioned before the fault. The DiR concept is applied in two dimensions: restoration blocking probability i.e., the probability that the disrupted connection is not recovered due to lack of network resources - and restoration time - i.e., the time necessary to complete the connection recovery procedure. Differentiation in the two dimensions is accomplished by proposing three preemption policies that allow high priority connections to preempt resources allocated to low priority connections. The three policies trade complexity, i.e., number of preempted connections, for better reliability differentiation. Obtained results indicate that by using the proposed preemption policies, it is possible to guarantee a significant differentiation of both restoration blocking probability and restoration time. By carefully choosing the preemption policy, the desired reliability degree can be obtained, while minimizing the number of preempted connections.