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Unformatted text preview: References 569 9.10 Consider a four-fiber BLSR that uses both span and ring switching. What are the functions required in network management to (a) coordinate span and ring switching mechanisms and (b) allow multiple failures to be restored? 9.11 Consider the example shown in Figure 9.18. Carefully characterize the set of simul- taneous multiple fiber cuts that can be handled by this arrangement. 9.12 Consider a five-node optical ring with one hub node and four access nodes. The traf- fic to be supported is one lightpath between each access node and the hub node. You can deploy either a two-fiber OCh-DPRing or a two-fiber OCh-SPRing in this appli- cation. No wavelength conversion is allowed inside the network, so each lightpath must use the same wavelength on every link along its path. Compare the amount of protection and working capacity needed for each case. Using a wavelength on a link counts as one unit of capacity. Would your answer change if wavelength conversion was allowed in both types of rings at any node in the ring? 9.13 Develop computer software that performs the following functions: (a) Allows you to input a network topology graph and a set of lightpaths (source- destinations). (b) Routes the lightpaths using a shortest-path algorithm. (c) Computes protection bandwidth in the network for two cases: 1 + 1 OCh protection and OCh shared mesh protection. For 1 + 1 OCh protection, use an algorithm to provide two disjoint shortest paths for each lightpath, such as the one in [ST84]. For shared mesh protection, use the following algorithm: for each failure i , determine the amount of protection capacity, C i (l) , that would be required on each link l in the network. Prove that the total protection capacity needed on link l is then simply max i C i (l) ....
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- Spring '09