Optimal and guaranteed alternative LSP for multiple failures

Fast rerouting mechanisms are being studied in order to provide fault tolerance for LSP in an MPLS network in case of node or link failure. For QoS provision, protected LSP are handled apart from non-protected LSP. Rerouting mechanisms when applied on protected LSP must take into account QoS requirements. This paper presents a mechanism that is able to handle multiple failures along an LSP while using an optimal alternative LSP. The rerouting decision is taken close to the point of failure that reduces the restoration time. The use of pre-established alternative LSP also reduces the restoration time and avoids blocking when looking for an alternative path. The proposal is based on a hybrid approach of segment repair and path repair and provides a new alternative LSP using dynamic rerouting once the protected one has been rerouted. In this way, there is always an alternative LSP for each protected LSP. The over all performance (recovery time, end-to-end delay, packet losses, and network resource utilization) is compared with existing protection mechanisms by simulation. The proposed hybrid approach, optimal and guaranteed alternative path (OGAP), avoids the possible use of a non-optimal alternative LSP to reroute the protected traffic and provides the flexibility of alternative route selection and setup as well as better resource utilization. Moreover, our proposal guarantees at least one alternative LSF at any time for the traffic on the protected LSP