Project 4 Reliability with Sliding Window Solution

Deliverable:




Submit the code you developed and any information required to compile and run your program in a .zip/.rar/.gz to the class Blackboard page by the due date.

Assignment:




The project will explore how to utilize C sockets to implement a reliable communication over a simulated unreliable link using a sliding window algorithm as discussed in class in C to send a text file one line at a time between a client and server using UDP. You have 3 options for implementing this:




Extra Credit (20 pts) Extend your Project 3 program to implement UDP sockets and implement the proposed reliability requirements.



Use the provided template code (client_udp.c, server_udp.c) to unreliably transmit a file from the client to the server using UDP, you must use only UDP to send packets.



Use some other POSIX socket-based program language to send UDP-based packets, you must implement the high-level reliability using only UDP. Use the same command like arguments as shown in the provided code. 1



Test System:




Run your assignment in the mininet platform. Your system will run on a basic topology with two hosts, h1 (IP: 10.0.0.1), and h2 (IP: 10.0.0.2), which communicate through a switch, s1.




Download the proj4_455.py and tux.txt from the Github site.



Open three different terminal windows.
Start mininet in terminal #1 with the following command: $ sudo mn -c



$ sudo mn --mac --switch ovsk --controller remote




Now, download POX into your home directory and start the POX SDN controller in terminal #2 utilizing the custom controller program, proj4_555.py. Download the controller and copy into the correct directory:



$ git clone http://github.com/noxrepo/pox $ mv proj4_555.py ~/pox/pox/misc/

Move to the “pox” directory and start the POX controller










$ cd pox




$ ./pox.py log.level --DEBUG misc.proj4_455




Verify that the controller connects to mininet, you should see the following output message:




INFO:core:POX 0.2.0 (carp) is up.




INFO:openflow.of_01:[00-00-00-00-00-01 1] connected




Now go back to terminal #1 and run the compiled client and server code mininet h2 ./server_udp output.txt &



mininet h1 ./client_udp 10.0.0.2 tux.txt




In terminal 3, view the newly created ouput.txt file. To verify it sent correctly, you should use the diff command as follows, the results should be empty diff tux.txt output.txt



Recommendations:




The following suggestions may be helpful:




Timeouts: You may want to implement sockets that only block for a short period of time, therefore allowing you to resend a lost data frames. To do so, please utilize the setsockopt() function which enables you to set the amount of time the socket will block for during a recvfrom() call.



struct timeval tv;

tv.tv_sec = 0;

tv.tv_usec = 1000;




…




if (setsockopt(s,SOL_SOCKET, SO_RCVTIMEO,&tv,sizeof(tv)) < 0) { perror("PError");

}




Window Size=10: You should keep a sender buffer of 10 previous lines in case resends are needed.
Sequence Numbers & Acks: You’ll need to use sequence numbers and acknowledgements, the number can just be represented by the first byte of each packet’s payload.
Handle drops: The network will both randomly drop packets, so you should test and verify that your reliability mechanism can handle this.
Termination: To signal the termination of a connection, you can send a special sequence/acknowledgement number (e.g., 0xffff). It is possible that this is message is also dropped, but don’t worry about acknowledging it.



Max line lengths: You can safely assume that each line sends at most 80 characters