Consider a general topology.
• The synchronous version of the distance – vector algorithm is used to compute the entries in the distance table.
• The nodes in the network are only aware of the costs of their immediate neighbors.
The following procedure gives the maximum number of iterations required for the algorithm converges:
• The node exchanges the distance tables with its neighbors in each iteration.
• For example, let node A represents the source node, and node B is a neighbor of node A, then all the neighbors of node B (which are one or two hops from node A) are aware of the shortest cost path to node A after the first iteration.
• Let d (be the diameter of the network) represents the length of the longest path without loops between any two nodes in the network.
• Using the above example, after d-1 iterations, all nodes will know the shortest path cost of d or fewer hops to all other nodes.
• Any path with greater than d hops consists of loops which leads the result of the algorithm to converge in at most d-1 iterations.
• When the Distance Vector algorithm runs as a result of a change in the cost of a link, then there is no priori bound on the number of iterations required until convergence and unless a bound on link costs are specified.
Therefore, the distance vector algorithm converges in at most d -1 iterations.
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