Write a program to simulate Go back N and Selective Repeat Modes of Sliding Window Protocol in Peer-to-Peer mode
CNS Assignment 4
Code :
#include<iostream>
#include<ctime>
#include<cstdlib>
using namespace std;
int main()
{
int nf,N;
int no_tr=0;
srand(time(NULL));
cout<<"Enter the number of frames : ";
cin>>nf;
cout<<"Enter the Window Size : ";
cin>>N;
int i=1;
while(i<=nf)
{
int x=0;
for(int j=i;j<i+N && j<=nf;j++)
{
cout<<"Sent Frame "<<j<<endl;
no_tr++;
}
for(int j=i;j<i+N && j<=nf;j++)
{
int flag = rand()%2;
if(!flag)
{
cout<<"Acknowledgment for Frame "<<j<<endl;
x++;
}
else
{ cout<<"Frame "<<j<<" Not Received"<<endl;
cout<<"Retransmitting Window"<<endl;
break;
}
}
cout<<endl;
i+=x;
}
cout<<"Total number of transmissions : "<<no_tr<<endl;
return 0;
}
Output :
Code :
#include<iostream>
using namespace std;
#include<conio.h>
#include<stdlib.h>
#include<time.h>
#include<math.h>
#define TOT_FRAMES 500
#define FRAMES_SEND 10
class sel_repeat
{
private:
int fr_send_at_instance;
int arr[TOT_FRAMES];
int send[FRAMES_SEND];
int rcvd[FRAMES_SEND];
char rcvd_ack[FRAMES_SEND];
int sw;
int rw; //tells expected frame
public:
void input();
void sender(int);
void receiver(int);
};
void sel_repeat::input()
{
int n; //no. of bits for the frame
int m; //no. of frames from n bits
int i;
cout<<"Enter the no. of bits for the sequence no. : ";
cin>>n;
m=pow(2,n);
int t=0;
fr_send_at_instance=(m/2);
for(i=0;i<TOT_FRAMES;i++)
{
arr[i]=t;
t=(t+1)%m;
}
for(i=0;i<fr_send_at_instance;i++)
{
send[i]=arr[i];
rcvd[i]=arr[i];
rcvd_ack[i]='n';
}
rw=sw=fr_send_at_instance;
sender(m);
}
void sel_repeat::sender(int m)
{
for(int i=0;i<fr_send_at_instance;i++)
{
if(rcvd_ack[i]=='n')
cout<<"SENDER : Frame "<<send[i]<<" is sent\n";
}
receiver(m);
}
void sel_repeat::receiver(int m)
{
time_t t;
int f;
int j;
int f1;
int a1;
char ch;
srand((unsigned)time(&t));
for(int i=0;i<fr_send_at_instance;i++)
{
if(rcvd_ack[i]=='n')
{
f=rand()%10;
//if f=5 frame is discarded for some reason
//else frame is correctly recieved
if(f!=5)
{
for(int j=0;j<fr_send_at_instance;j++)
if(rcvd[j]==send[i])
{
cout<<"reciever:Frame"<<rcvd[j]<<"recieved correctly\n";
rcvd[j]=arr[rw];
rw=(rw+1)%m;
break;
}
int j;
if(j==fr_send_at_instance)
cout<<"reciever:Duplicate frame"<<send[i]<<"discarded\n";
a1=rand()%5;
//if al==3 then ack is lost
//else recieved
if(a1==3)
{
cout<<"(acknowledgement "<<send[i]<<" lost)\n";
cout<<"(sender timeouts-->Resend the frame)\n";
rcvd_ack[i]='n';
}
else
{
cout<<"(acknowledgement "<<send[i]<<" recieved)\n";
rcvd_ack[i]='p';
}
}
else
{int ld=rand()%2;
//if =0 then frame damaged
//else frame lost
if(ld==0)
{
cout<<"RECEIVER : Frame "<<send[i]<<" is damaged\n";
cout<<"RECEIVER : Negative Acknowledgement "<<send[i]<<" sent\n";
}
else
{
cout<<"RECEIVER : Frame "<<send[i]<<" is lost\n";
cout<<"(SENDER TIMEOUTS-->RESEND THE FRAME)\n";
}
rcvd_ack[i]='n';
}
}
}
for(int j=0;j<fr_send_at_instance;j++)
{
if(rcvd_ack[j]=='n')
break;
}
int i=0;
for(int k=j;k<fr_send_at_instance;k++)
{
send[i]=send[k];
if(rcvd_ack[k]=='n')
rcvd_ack[i]='n';
else
rcvd_ack[i]='p';
i++;
}
if(i!=fr_send_at_instance)
{
for(int k=i;k<fr_send_at_instance;k++)
{
send[k]=arr[sw];
sw=(sw+1)%m;
rcvd_ack[k]='n';
}
}
cout<<"Want to continue";
cin>>ch;
cout<<"\n";
if(ch=='y')
sender(m);
else
exit(0);
}
int main()
{
sel_repeat sr;
sr.input();
}
Output
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