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node2.c
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node2.c
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#include <stdio.h>
extern struct rtpkt {
int sourceid; /* id of sending router sending this pkt */
int destid; /* id of router to which pkt being sent
(must be an immediate neighbor) */
int mincost[4]; /* min cost to node 0 ... 3 */
};
extern int TRACE;
extern int YES;
extern int NO;
extern float clocktime;
struct distance_table
{
int costs[4][4];
} dt2;
/* students to write the following two routines, and maybe some others */
void rtinit2()
{
printf("\nrtinit2 invoked at time %f \n", clocktime);
/*initialize distance table*/
for (int i = 0; i < 4; i++)
for (int j = 0; j < 4; j++)
dt2.costs[i][j] = 999;
/*updating costs based on given initial network topology*/
dt2.costs[0][0] = 3;
dt2.costs[0][2] = 3;
dt2.costs[1][1] = 1;
dt2.costs[1][2] = 1;
dt2.costs[2][2] = 0;
dt2.costs[3][2] = 2;
dt2.costs[3][3] = 2;
/*printing the initial distance table*/
printdt2(&dt2);
/*make dv packets to send to neighbours*/
struct rtpkt pkt0, pkt1, pkt3;
pkt0.sourceid = 2;
pkt0.destid = 0;
pkt1.sourceid = 2;
pkt1.destid = 1;
pkt3.sourceid = 2;
pkt3.destid = 3;
for (int i = 0; i < 4; i++)
{
pkt0.mincost[i] = dt2.costs[i][2];
pkt1.mincost[i] = dt2.costs[i][2];
pkt3.mincost[i] = dt2.costs[i][2];
}
/*sending dv packets to neighbours*/
tolayer2(pkt0);
tolayer2(pkt1);
tolayer2(pkt3);
}
void rtupdate2(rcvdpkt)
struct rtpkt *rcvdpkt;
{
printf("\nrtupdate2 invoked at time %f \n", clocktime);
if (rcvdpkt->destid != 2) //wrong destination check
return;
int j = rcvdpkt->sourceid; /*srouce id signifies the column vector in dt2 that could be updated potentially*/
int flag = 0; /*flag is set to 1 in case there is an update in the distance table*/
printf("\nPacket rcvd at node 2 from node %d \n", j);
/*traversing column j of distance table to see if it needs to be updated*/
for (int i = 0; i < 4; i++)
{
if (dt2.costs[i][j] > dt2.costs[j][2] + rcvdpkt->mincost[i])
{
dt2.costs[i][j] = dt2.costs[j][2] + rcvdpkt->mincost[i];
if(i != 2)
flag = 1;
}
}
if (flag == 1) //change in dt2 detected!
{
printf("\nDistance table at node 2 updated: \n");
printdt2(&dt2);
struct rtpkt pkt0, pkt1, pkt3;
pkt0.sourceid = 2;
pkt0.destid = 0;
pkt1.sourceid = 2;
pkt1.destid = 1;
pkt3.sourceid = 2;
pkt3.destid = 3;
pkt0.mincost[2] = 0;
pkt1.mincost[2] = 0;
pkt3.mincost[2] = 0;
for (int i = 0; i < 4; i++)
{
if (i == 2)
continue;
pkt0.mincost[i] = min(dt2.costs[i][0], dt2.costs[i][1], dt2.costs[i][3]);
pkt1.mincost[i] = min(dt2.costs[i][0], dt2.costs[i][1], dt2.costs[i][3]);
pkt3.mincost[i] = min(dt2.costs[i][0], dt2.costs[i][1], dt2.costs[i][3]);
}
printf("\nSending routing packets to nodes 0, 1 and 3 with following mincost vector: \n");
for (int i = 0; i < 4; i++)
printf("%d\t", pkt0.mincost[i]);
printf("\n");
/*sending dv packets to neighbours*/
tolayer2(pkt0);
tolayer2(pkt1);
tolayer2(pkt3);
}
}
printdt2(dtptr)
struct distance_table *dtptr;
{
printf(" via \n");
printf(" D2 | 0 1 3 \n");
printf(" ----|-----------------\n");
printf(" 0| %3d %3d %3d\n",dtptr->costs[0][0],
dtptr->costs[0][1],dtptr->costs[0][3]);
printf("dest 1| %3d %3d %3d\n",dtptr->costs[1][0],
dtptr->costs[1][1],dtptr->costs[1][3]);
printf(" 3| %3d %3d %3d\n",dtptr->costs[3][0],
dtptr->costs[3][1],dtptr->costs[3][3]);
}