Rapid protection schemes in an all-optical packet metro ring

This study adapts the two conventional protection methods, 1+1 and 1:1, to an all-optical, time-slotted packet ring designed for metropolitan area networks. The two corresponding protection schemes, Premium and Regular, rely on OAM messages that can be carried in each time slot. Each scheme offers packet level protection and maintains a congestion free and simple recovery mechanism in case of single failure. The upper bound for failure recovery time is very low as it is limited to the ring cycle time, which is about 2ms (much less than the 50ms SDH recovery time). The results suggest two very robust and efficient protection methods. In premium method network experiences no loss, whereas the loss period for Regular traffic is limited to a portion of the Round Trip Time. Preliminary dimensioning results are obtained under the assumption that the ring is dimensioned to support a single link failure. The difference between resources for Premium and Regular schemes depends on the traffic matrix and may be negligible for the very common concentration/distribution scenario. In the uniform traffic case, the cost of a dual ring with Regular protection is shown to be very close to the cost of a single, unprotected ring.