, the low-priority traffic that is routed onto the spare capacity, which has to be exploited for recovery is blocked, and the connection is lost. This is the lower service class in terms of availability. 2. Service Class 1: Best Effort Traffic. This service class collects all the services, like web browsing and many other consumer services, that run onto a specifically provi- sioned capacity, but are not protected. If a failure occurs, on a working link where a best effort LSP is routed, it is lost up to the repair of the link. 3. Service Class 2: Standard Traffic. This is a class composed by LSPs that are protected via a type 1 restoration at the MPLS layer. It is important to notice that services of the classes 1 and 2 can run on the same physical fiber and even in the same optical GLSP. As a matter of fact, class 2 traffic restoration is managed by MPLS on layer 2. Thus if a fiber containing both class 1 and class 2 services is cut, the LSR that are at the ends of the involved GLSPs will start the rerouting of the failed class 2 LSPs, while will start signaling over the GMPLS network and through the UNI interface toward layer 3 to advertise that the involved best effort LSPs have been lost. In this case RF1 is very near to one, but not exactly equal. 4. Service Class 3: High Availability Traffic. This traffic is protected via a multilayer pro- tection with the R-R method. This class of LSPs has a very high resilience toward many type of failure events, as we have evidenced in the last section, besides a complete recovery ability toward single and double link cut. Class 3 services can- not run on the same fibers where classes 1 and 2 services run, since they are pro- tected also at the optical layer by a restoration mechanism. We will see that they can run in the same fibers of class 4 services, but not in the same wavelength. 5. Service Class 4: Mission Critical Traffic. This is the traffic that cannot be lost, but in cases of cataclysmic disasters like extended earthquakes or strategic nuclear attacks. The pr