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Essential CDS Algorithm Uses 2-hop neighbor information obtained from Hellos. Essential CDS Algorithm: If the router has a larger (RtrPri, RID) than all of its neighbors, it selects itself as a DR, and selects all neighbors as Dependent Neighbors, which become adjacent. (Same as DR selection in OSPF.) Else, if there does not exist a path (based on 2-hop neighbor information) from the neighbor j with largest (RtrPri, RID) to some other neighbor, via neighbors with larger values of (RtrPri, RID), then the router selects itself as a DR, and selects j and each neighbor for which such a path does not exist, as Dependent Neighbors, which become adjacent. BDR selection is similar, but requires 2 node-disjoint paths from neighbor j to each other neighbor, to avoid selecting itself as BDR. “Persistent” version gives higher priority to existing DRs and BDRs. Algorithm runs in O(d2) time, where d is the number of neighbors. |