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IS-IS Network Design Solutions by Scott Sturgess, Abe Martey

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Chapter 6. The Shortest Path First Algorithm

The essence of a routing protocol is to collect routing information about the networking environment and to determine the best paths to all known destinations. As discussed in Chapter 2, “Introduction to the IS-IS Routing Protocol,” these functions are performed by two processes within the architecture of the IS-IS protocol: the update process and the decision process. The update process is responsible for building the IS-IS database and ensuring its integrity. The decision process uses the shortest path first (SPF) algorithm to calculate the best paths to all known destinations based on the information in the Link-State database. The SPF algorithm works by computing the shortest path tree from a specific ...

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