Comparison of protection cost at IP or WDM layer

We consider wavelength routed networks used to overlay a logical topology over a WDM optical infrastructure. We consider the additional capacity required to manage single fiber fault. In particular, we consider both optical protection mechanism in which additional wavelengths are reserved to face faults (WDM protection), and IP restoration mechanisms, in which additional link capacity is deployed to assure no traffic is lost after re-routing of traffic flows affected by the fiber fault. By considering simple yet common scenarios in which bidirectional rings are considered as physical topology while regular topologies are considered at the logical layer, we are able to obtain analytical results to compare the two fault management schemes. Results shows that optical protection in general requires fewer additional capacity resources. When considering large number of nodes, however, the advantage of WDM protection tends to become less attractive