Listributed restoration algorithms have been recently studied for ATM network [1-5], but perfect spare capacity assignment approach associated with ATM restoration algorithms is still underdevelopment. In this paper, we propose an efficient spare capacity allocation strategy for an ATM survival network, in order to obtain the best cost-performance feature. The approach consists of two phases: network planning and network operating. In the network planning phase,spare capacity is reserved in an ATM network for network growth in the near future and for failure. Our strategy is only for restoration purpose. In the network operating phase, we suggest a hybrid restoration mechanism for ATM network, which integrates a backup-VP restoration method [2] and a distributed flooding algorithm [3], the mechanism is able to handle a multiple-link or multiple-node failure. Spare capacity on every link of ATM VP-based network is taken as the object of manipulation, we derive three restraint condition formulas for a new workirameters: spare capacity ratio and the spare capacity shared ratio of each link. Through computer simulation, the impact of these two parameters is studied, and the value of them are adjusted according to the dynamic load of an ATM network. As a result,the optimum amount and location of spare capacity in the ATM network, and optimum division of the restoration responsibility between the backup-VP method and the distributed flooding algorithm is obtained, under the given survival performance requirements (e.g. restoration ratio, restoration time ).Thus the total survivability cost of ATM network is minimized.
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