Protection Switching and Rerouting in MPLS

Multi-protocol Label Switching (MPLS) has become an attractive technology of choice for Internet backbone service providers. MPLS recovery mechanisms are increasing in popularity because they can guarantee fast restoration and high QoS assurance. To provide dependable services MPLS networks make use of a set of procedures (detection, notification and fault recovery) which seek to ensure appropriate protection for the traffic carried in the label switched paths (LSPs). When a fault happens in the active LSP, the recovery scheme must redirect the traffic to a recovery path (the protection LSP or recovery LSP) which bypasses the fault. The two basic recovery models used to redirect traffic are rerouting and protection switching. Protection switching is faster than rerouting but cannot handle simultaneous faults in the active and the recovery path. On the other hand, rerouting is generally slow, and cannot offer QoS guaranties upon failure, but can use resources in a more efficient way.