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Distance Vector Routing (DVR) Protocol

A distance-vector routing (DVR) protocol requires that a router inform its neighbors of topology changes periodically. Historically known as the old ARPANET routing algorithm (or known as Bellman-Ford algorithm).

Bellman Ford Basics – Each router maintains a Distance Vector table containing the distance between itself and ALL possible destination nodes. Distances,based on a chosen metric, are computed using information from the neighbors’ distance vectors.

Information kept by DV router -
Distance Vector Table Initialization -

Distance Vector Algorithm –

  1. A router transmits its distance vector to each of its neighbors in a routing packet.
  2. Each router receives and saves the most recently received distance vector from each of its neighbors.
  3. A router recalculates its distance vector when:
    • It receives a distance vector from a neighbor containing different information than before.
    • It discovers that a link to a neighbor has gone down.

The DV calculation is based on minimizing the cost to each destination

Dx(y) = Estimate of least cost from x to y 
C(x,v) =  Node x knows cost to each neighbor v
Dx   =  [Dx(y): y ? N ] = Node x maintains distance vector
Node x also maintains its neighbors' distance vectors
– For each neighbor v, x maintains Dv = [Dv(y): y ? N ]

Note –

Example – Consider 3-routers X, Y and Z as shown in figure. Each router have their routing table. Every routing table will contain distance to the destination nodes.


Consider router X , X will share it routing table to neighbors and neighbors will share it routing table to it to X and distance from node X to destination will be calculated using bellmen- ford equation.

 Dx(y) = min { C(x,v) + Dv(y)} for each node y ? N

As we can see that distance will be less going from X to Z when Y is intermediate node(hop) so it will be update in routing table X.


Similarly for Z also –

Finally the routing table for all –



Advantages of Distance Vector routing –

  1. GATE CS 2011, Question 52
  2. GATE CS 2011, Question 53
  3. GATE CS 2010, Question 54
  4. GATE CS 2010, Question 55
  5. GATE IT 2005, Question 28
  6. GATE CS 2014 (Set 1), Question 33
  7. GATE IT 2008, Question 65
  8. GATE CS 2014 (Set 2), Question 65

References –

Distance vector routing – wikipedia
www.eecs.yorku.ca

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