Distance Vector Routing Algorithm in C

Distance Vector Routing Algorithm in C

In computer communication theory relating to packet-switched networks, a distance-vector routing protocol is one of the two major classes of routing protocols, the other major class being the link-state protocol. A distance-vector routing protocol uses the Bellman-Ford algorithm to calculate paths.

A distance-vector routing protocol requires that a router informs its neighbors of topology changes periodically and, in some cases, when a change is detected in the topology of a network. Compared to link-state protocols, which require a router to inform all the nodes in a network of topology changes, distance-vector routing protocols have less computational complexity and message overhead.

Distance Vector means that Routers are advertised as vector of distance and direction. 'Direction' is represented by next hop address and exit interface, whereas 'Distance' uses metrics such as hop count.

Routers using distance vector protocol do not have knowledge of the entire path to a destination. Instead DV uses two methods:

1. Direction in which or interface to which a packet should be forwarded.
2. Distance from its destination.

Examples of distance-vector routing protocols include Routing Information Protocol Version 1 & 2, RIPv1 and RIPv2 and IGRP. EGP and BGP are not pure distance-vector routing protocols because a distance-vector protocol calculates routes based only on link costs whereas in BGP, for example, the local route preference value takes priority over the link cost. 

Distance vector algorithm routing implementation in C

#include<stdio.h>

struct node

{

    unsigned dist[20];

    unsigned from[20];

}rt[10];

int main()

{

    int dmat[20][20];

    int n,i,j,k,count=0;

    printf("\nEnter the number of nodes : ");

    scanf("%d",&n);

    printf("\nEnter the cost matrix :\n");

    for(i=0;i<n;i++)

        for(j=0;j<n;j++)

        {  

            scanf("%d",&dmat[i][j]);

            dmat[i][i]=0;

            rt[i].dist[j]=dmat[i][j];

            rt[i].from[j]=j;

        }

        do

        {  

            count=0;

            for(i=0;i<n;i++)

            for(j=0;j<n;j++)

            for(k=0;k<n;k++)

                if(rt[i].dist[j]>dmat[i][k]+rt[k].dist[j])

                {

                    rt[i].dist[j]=rt[i].dist[k]+rt[k].dist[j];

                    rt[i].from[j]=k;

                    count++;

                }

        }while(count!=0);

        for(i=0;i<n;i++)

        {

            printf("\n\nState value for router %d is \n",i+1);

            for(j=0;j<n;j++)

            {

                printf("\t\nnode %d via %d Distance%d",j+1,rt[i].from[j]+1,rt[i].dist[j]);

            }

        }  

    printf("\n\n");

}

Makefile

1 2 3 4 5

a.out:distanceVector.c     gcc -ggdb distanceVector.c PHONY:clean clean:     rm a.out *~

Example output

Enter the number of nodes : 4

Enter the cost matrix :
0 3 5 99
3 0 99 1
5 4 0 2
99 1 2 0


State value for router 1 is
   
node 1 via 1 Distance0   
node 2 via 2 Distance3   
node 3 via 3 Distance5   
node 4 via 2 Distance4

State value for router 2 is
   
node 1 via 1 Distance3   
node 2 via 2 Distance0   
node 3 via 4 Distance3   
node 4 via 4 Distance1

State value for router 3 is
   
node 1 via 1 Distance5   
node 2 via 4 Distance3   
node 3 via 3 Distance0   
node 4 via 4 Distance2

State value for router 4 is
   
node 1 via 2 Distance4   
node 2 via 2 Distance1   
node 3 via 3 Distance2   
node 4 via 4 Distance0

Conclusion:

Hence the distance vector routing algorithm configured and implemented.