Distance Vector Routing Algorithm

AIM: Take an example subnet graph with weights indicating delay between nodes. Now obtain Routing table at each node using distance vector routing algorithm.

DESCRIPTION:

- In distance vector routing, each router periodically shares its knowledge about the entire internet with its neighbors.

- The three keys to understanding how this algorithm works are as follows:

- Sharing knowledge about the entire autonomous system.

- Sharing only with neighbors.

- Sharing at regular intervals.

- Every router keeps a routing table that has one entry for each destination network which the router aware.

ALGORITHM:

Add one hop to the hop count for each advertised destination.

Repeat the following steps for each advertized destination

If(destination not in the routing table)

Add the advertized information to the table.

Else

If(next-hop field is the same)

Replace entry in the table with the advertised one.

Else

If( advertized hop count smaller than one in table)

Replace entry in Routing table.

C CODE FOR DISTANCE VECTOR ROOTING

#include<stdio.h>

#include<conio.h>

#include<string.h>

main()

{

char c1[]={'A','I','H','K','\0'};

char c2[]={'A','B','C','D','E','F','G','H','I','J','K','L'};

int doj[]={8,10,12,6};

int i,j,min,delay[5][12],res,k=0,l=0,pre[5];

clrscr();

for(i=0;i<4;i++)

{

for(j=0;j<12;j++)

{

printf("\nenter delay from %c to %c",c1[i],c2[i]);

scanf("%d",&delay[i][j]);

}

}

min=1000;

for(j=0;j<12;j++)

{

for(i=0;i<4;i++)

{

res=delay[i][j]+doj[i];

if(res<min)

{

min=res;

k=i;

}

}

delay[4][j]=min;

pre[l++]=k;

min=1000;

}

clrscr();

for(i=0;i<12;i++)

{

if(i==9)

delay[4][j]=0;

printf("\nDelay from j to %c is %d",c2[i],delay[4][j]);

if(i!=9)

printf("\t by the mode %c",c1[pre[i]]);

else

printf("\t by the node");

}

getch();
}