Protected Connection Provisioning with Low Availability Overfulfillment in Meshed Core Networks

Abstract:
Network operators sell connection services to their customers. The corresponding service contracts typically include a service level agreement (SLA) which defines a guaranteed availability level per month. An availability exceeding the SLA level means that the network operator complies with the SLA. A lower availability results in contractual penalties. Therefore, the probability of SLA compliance is a key figure for the operator. To adjust the compliance probability, many operators apply protection mechanisms, which tie up precious network resources to provide backup capacity. Therefore, it is desirable to dedicate only as many network resources to protection as necessary to reach a sufficiently high probability of SLA compliance – the operator’s self-defined compliance target. However, in practice, this is difficult to realize because using protection, the amount of resources and, consequently, the compliance probability cannot be selected continuously. Adding protection to a connection service makes its compliance probability jump up, possibly to a level far above the operator’s compliance target. The result is overfulfillment at the cost of precious network resources. In this paper, we propose an admission and routing approach that reduces said overfulfillment, frees network resources and by that allows more services to be accommodated in the network. We use a stochastic approach to estimate a service’s probability of SLA compliance. Probability that exceeds the operator’s compliance target is accumulated as surplus and allows other services to be accepted with a compliance probability below the operator’s original compliance target. With this approach, the resulting SLA compliance ratio over all services matches the compliance target closely, i.e., the overfulfillment is reduced. We evaluate our mechanism in a simulation study covering several core network topologies. It is shown that the availability overfulfillment can be reduced or even eliminated and that the service blocking ratio can be decreased significantly.