Selective Repeat Protocol

Description

Selective Repeat is a sliding window protocol used in network communications to achieve reliable data transmission over an unreliable network. Unlike Go-Back-N, Selective Repeat allows the receiver to individually acknowledge correctly received frames, and the sender retransmits only those frames for which it does not receive an acknowledgment within a specified timeout period.

C++ Code

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <unistd.h>

using namespace std;

const int WINDOW_SIZE = 4;
const int TIMEOUT = 3;

bool sendData(int frameNumber) {
    srand(time(0));
    bool ackReceived = (rand() % 10 < 8);

    if (ackReceived) {
        cout << "Frame " << frameNumber << " sent successfully." << endl;
        return true;
    } else {
        cout << "Frame " << frameNumber << " not acknowledged. Retransmitting only this frame..." << endl;
        return false;
    }
}

int main() {
    int base = 1;
    int nextSeqNum = 1;
    
    while (base <= 5) {
        while (nextSeqNum < base + WINDOW_SIZE && nextSeqNum <= 5) {
            bool ack = sendData(nextSeqNum);

            if (ack) {
                nextSeqNum++;
            }
        }

        sleep(TIMEOUT);
    }

    cout << "Data transmission completed." << endl;
    return 0;
}

Time and Space Complexity

Operation	Time Complexity	Space Complexity
Selective Repeat Protocol	O(n)	O(1)

Where:

• n: Number of frames to be transmitted.

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