To achieve these expectations, we'll need to implement a reliable data transfer protocol over UDP with congestion control and flow control mechanisms. Here's an outline of how we can approach this:

1. Packet Structure: Define a packet structure that includes sequence numbers, acknowledgment numbers, checksums, and data payload.

2. Sender Implementation (rsend):

   • Split the file into chunks.
   • Implement a sliding window mechanism to control the number of unacknowledged packets.
   • Use selective repeat ARQ (Automatic Repeat reQuest) to handle lost packets.
   • Implement congestion control mechanisms like slow start and congestion avoidance using algorithms like TCP Tahoe or TCP Reno.
   • Calculate and verify checksums for data integrity.
   • Handle flow control based on receiver's acknowledgment window size.
   • Send packets using UDP sockets.

3. Receiver Implementation (rrecv):

   • Receive packets using UDP sockets.
   • Implement a sliding window for receiving and buffering packets.
   • Send acknowledgments for received packets and handle duplicate acknowledgments.
   • Write received data to the destination file with consideration of the write rate limit.
   • Signal the sender to adjust transmission rate based on flow control.
   • Calculate and verify checksums for data integrity.

4. Main Functions:

   • Implement main functions in sender.c and receiver.c to handle command-line arguments and invoke the data transfer operations.

5. Testing and Evaluation:

   • Test the protocol under different network conditions, including dropped packets and varying bandwidth.
   • Evaluate the protocol's performance against the provided expectations (E1-E8), ensuring fairness, throughput, and adherence to flow control.

In further detail:

1. Packet Structure:

Define a packet structure that includes fields for sequence number, acknowledgment number, checksum, and data payload.

struct Packet {
    unsigned int seq_num;
    unsigned int ack_num;
    unsigned int checksum;
    char data[MAX_DATA_SIZE];
};

2. Sender Implementation (rsend):

Here's an outline of steps to implement rsend:

a. Split the file into chunks:

• Read the file in chunks of a certain size.

b. Sliding Window Mechanism:

• Maintain a sender window to control the number of unacknowledged packets.
• Update the window based on acknowledgments received.

c. Selective Repeat ARQ:

• Retransmit packets that are not acknowledged within a certain timeout period.

d. Congestion Control:

• Implement slow start and congestion avoidance algorithms.
• Adjust the sender window size based on congestion signals.

e. Flow Control:

• Monitor receiver's acknowledgment window size.
• Adjust transmission rate based on receiver's flow control signals.

f. UDP Socket Communication:

• Send packets using UDP sockets.

3. Receiver Implementation (rrecv):

Here's an outline of steps to implement rrecv:

a. Receiving and Buffering:

• Receive packets using UDP sockets.
• Buffer received packets in a receive window.

b. Sending Acknowledgments:

• Send acknowledgments for received packets.
• Handle duplicate acknowledgments.

c. Writing to Destination File:

• Write received data to the destination file.
• Respect the write rate limit specified.

d. Signaling Flow Control:

• Signal the sender to adjust transmission rate based on flow control.

e. UDP Socket Communication:

• Receive packets and send acknowledgments using UDP sockets.

4. Main Functions:

Implement main functions in sender.c and receiver.c to handle command-line arguments and invoke the data transfer operations.

5. Testing and Evaluation:

Test the protocol under different network conditions, including dropped packets and varying bandwidth. Evaluate the protocol's performance against the provided expectations (E1-E8).