A fast VP restoration scheme using ring-shaped sharable backup VPs

Using backup virtual paths (BVPs) has been proposed as one of the approaches to restore failed VPs in ATM networks. This scheme simplifies the restoration process but may require longer restoration time and larger number of VPIs. We propose the ring BVP (RBVP) scheme which overcomes the longer restoration time and the over-provisioning problems of the previously proposed BVP scheme. The RBVP scheme maintains a number of ring shaped BVPs for each elementary cycle (e-cycle; a shortest possible cycle containing a specific edge) and allows all the links in an e-cycle to share the corresponding RBVP for any link failures in the e-cycle. Since in the RBVP scheme the restoration process is localized only to a failed link, failed VPs can be restored almost twice faster than the previously proposed BVP scheme. Also since a RBVP can be shared by more than one VPs, a smaller number of VPIs are allocated for the VP restoration