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readme.md

MP2 reliable packet transfer

Requirement

Use UDP SOCK_DGRAM (UDP) to implement your own version of TCP.

  • tolerate packet drops,
  • allow other concurrent connections a fair chance,
  • must not be overly nice to other connections (should not give up the entire bandwidth to other connections)

Function prototype

sender_main.c

WJ

  • void reliablyTransfer(char* hostname, unsigned short int hostUDPport, char* filename, unsigned long long int bytesToTransfer).

This function should transfer the first bytesToTransfer bytes of filename to the receiver at hostname: hostUDPport correctly and efficiently, even if the network drops or reorders some of your packets.

  • Congestion control

    important, 20MB sender test

  • URL parse? No need, this is handled by Test program

receiver_main.c

WJX

  • void reliablyReceive(unsigned short int myUDPport, char* destinationFile)

This function is counterpart to reliablyTransfer , and should write what it receives to a file called destinationFile.

Points:

If our code can pass all the test case, that is fine test results:

Test 1: sanity check: transfer single byte failed: wrote 0 of 1 (text: ).

Test 2: transfer 50K failed: only received 0 of 50000 after 6s.

Test 3: utilize empty link failed: 0 of 65000000 were written.

Test 6: quick convergence failed: failed to send 20MB in 20s (receiver wrote 0 bytes)

Test 7: TCP friendliness failed: your process died or ended early. (note: it's being given 999000999000 as the numBytes argument)

Test 8: TCP friendliness with 1% loss failed: your process died or ended early. (note: it's being given 999000999000 as the numBytes argument) Q: where is T4, T5?

  • There are no test 4,5 for this MP. We removed these tests to make the MP less challenging. Q: how to avoid the problem of multiple RTT problem
  • However, sometimes will come out infinite loop problem, it is because the missing side effect of test 4, 5. The key is not to send too much packet at one time( never infinite loop sending pkt)

Test Case:

  • 391.txt
  • t391.txt -- 391.txt copy-paste*3
  • 10 mb test case
  • 50 MB txt file

test environment