Experiment 2

AIM: Implementation of bit stuffing

THEORY:

The data link layer is responsible for something called Framing, which is the division of stream of bits from network layer into manageable units (called frames). Frames could be of fixed size or variable size. In variable-size framing, we need a way to define the end of the frame and the beginning of the next frame. Bit stuffing is the insertion of non information bits into data. Note that stuffed bits should not be confused with overhead bits. Overhead bits are non-data bits that are necessary for transmission (usually as part of headers, checksums etc.)

CODE:

#include <stdio.h>

#include <stdlib.h>

#define MAX_SIZE 100

void bitStuffing(char* data, int* size) { // Function to perform bit stuffing

int count = 0;

int newSize = *size;

for (int i = 0; i < *size; i++) {

if (data[i] == '1') {

count++;

} else {

count = 0;

}

if (count == 5) {

count = 0;

for (int j = newSize; j > i + 1; j--) { // Shift all elements to the right by one

data[j] = data[j - 1];

}

data[i + 1] = '0'; // Insert '0' after the fifth consecutive '1'

newSize++;

count = 0;

}

*size = newSize;

data[*size] = '\0'; // Null-terminate the string

}

void bitDestuffing(char* data, int* size) { // Function to perform bit destuffing

int count = 0;

int newSize = *size;

for (int i = 0; i < newSize; i++) {

if (data[i] == '1') {

count++;

} else {

count = 0;

}

if (count == 5 && i < newSize - 1 && data[i + 1] == '0') {

for (int j = i + 1; j < newSize; j++) { // Shift all elements to the left by one

data[j] = data[j + 1];

}

count = 0;

newSize--; // Adjust newSize after shifting

}

*size = newSize;

data[*size] = '\0'; // Null-terminate the string

}

int main() {

char data[MAX_SIZE];

int size;

printf("Enter the data (consisting of 0's and 1's): "); // Input data

scanf("%s", data);

for (size = 0; data[size] != '\0'; size++); // Calculate the size of the data

bitStuffing(data, &size); // Perform bit stuffing

printf("Stuffed data: %s\n", data);

bitDestuffing(data, &size); // Perform bit destuffing

printf("Destuffed data: %s\n", data);

return 0;

}

OUTPUT:

CONCLUSION:

The Data Link Layer plays a crucial role in organizing data into frames for reliable transmission. Framing helps divide the data stream into manageable units, ensuring proper synchronization between sender and receiver.In variable-size framing, techniques like Bit Stuffing are used to differentiate frames. Bit Stuffing involves inserting extra bits into the data to prevent accidental frame boundary confusion. These stuffed bits are removed at the receiver end through Bit Destuffing, ensuring the original data is recovered correctly. This approach ensures error-free data transmission and is widely used in serial communication protocols like HDLC and PPP.