Destination-Sequenced Distance-Vector (DSDV)
•When X receives information from Y about a route to Z
–Let destination sequence number for Z at X be S(X), S(Y) is sent from Y
–If S(X) > S(Y), then X ignores the routing information received from Y
–If S(X) = S(Y), and cost of going through Y is smaller than the route known to X, then X sets Y as the next hop to Z
–If S(X) < S(Y), then X sets Y as the next hop to Z, and S(X) is updated to equal S(Y)
DSDV Protocol
•Packets are transmitted between the nodes using route tables stored at each node.
•Each route tablelists all available destinations and the number of hops to each destination.
•For each destination, a node knows which of its neighbours leads to the shortest path to the destination.
•Consider a source node Sand a destination node D.
•Each route table entry in S is tagged with a sequence number that is originated by the destination node.
•For example, the entry for D is tagged with a sequence number that Sreceived from D (may be through other nodes).
•We need to maintain the consistency of the route tables in a dynamically varying topology.
•Each node periodically transmits updates. This is done by each node when significant new information is available.
•The route-update messages indicate which nodes are accessible from each node and the number of hops to reach them.
•We consider the hop-count as the distance between two nodes. However, the DSDV protocol can be modified for other metrics as well.
•When X receives information from Y about a route to Z
–Let destination sequence number for Z at X be S(X), S(Y) is sent from Y
–If S(X) > S(Y), then X ignores the routing information received from Y
–If S(X) = S(Y), and cost of going through Y is smaller than the route known to X, then X sets Y as the next hop to Z
–If S(X) < S(Y), then X sets Y as the next hop to Z, and S(X) is updated to equal S(Y)
DSDV Protocol
•Packets are transmitted between the nodes using route tables stored at each node.
•Each route tablelists all available destinations and the number of hops to each destination.
•For each destination, a node knows which of its neighbours leads to the shortest path to the destination.
•Consider a source node Sand a destination node D.
•Each route table entry in S is tagged with a sequence number that is originated by the destination node.
•For example, the entry for D is tagged with a sequence number that Sreceived from D (may be through other nodes).
•We need to maintain the consistency of the route tables in a dynamically varying topology.
•Each node periodically transmits updates. This is done by each node when significant new information is available.
•The route-update messages indicate which nodes are accessible from each node and the number of hops to reach them.
•We consider the hop-count as the distance between two nodes. However, the DSDV protocol can be modified for other metrics as well.
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