Distance Vector Routing Protocol


In computer networks subject, when we study the network layer, about the different routing protocols used, DVR is the one that was used.

Basics :
It is an Intra-Routing Protocol/Interior Routing Protocol. This means that within an autonomous system when routers want to know about the network and connections that exist, then they use this. You can understand this like a small class in a school. If you want to know more about the different students and the connections that exist in your small own same class, then you use DVR.

Process :
1. I tell my neighbor whatever I know.
2. You do the same.
3. We both keep the best information about the outside world that we want to keep.

1. Routers share their routing tables with their immediate neighbors.
2. Every router does the same with their immediate routers. Routing table basically contains a list of all nodes that are reachable from a router, their total distance from the router, and extra details like via which intermediate node they are connected(or NULL if directly connected).
3. If you can already reach to a node C in 2 hops and B tells you that he can reach C in 2 hops. Then you see that via B you will reach in 3 hops( 1 to reach B + 2 hops that he told) via B, and directly you can reach in 2 hops. So, obviously you will go using the path you already knew, not via B.

Setbacks :
In any network, some links fall, some generate. Routers do not know about far away changes as they are only in touch with their direct neighbors about the sudden changes. So there is this problem of slow change.

Further Readings :
Count to infinity problem, further variants of DVR, Link State Routing Protocol.



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