Project 3: reliable transport

What is what

File	Role
gbn.py	yours: Sender.send(); the receiver is given
sr.py	yours: Sender.send() and Receiver.receive()
stopwait.py	given: stop-and-wait, with the timer, cumulative ACKs and the FIN/FINACK close
packet.py	given: packet format, Internet checksum, MSS 1000
channel.py	given: simulated link for the offline checks
selfcheck.py	given: public checks over that link
transfer.py	given: file transfer over UDP
experiments.py	given: loss and window sweeps, writes results.json
challenge.py	given: client for the class challenge server
PROTOCOL.md	given: the challenge control exchange

The grader restores every given file from a clean copy, so leave them as they are.

Run

Python 3, standard library only.

python3 selfcheck.py                 # both protocols
python3 selfcheck.py gbn             # one side
python3 experiments.py               # both sweeps
python3 experiments.py loss          # loss sweep only
python3 experiments.py window        # window sweep only
python3 challenge.py B-gbn --student your_id

A side that is still unwritten prints SKIP after about 30 seconds per check, so run one side at a time while you write code.

The experiments need ip netns and tc netem. In the course container:

docker run --rm --privileged -v "$PWD/..":/work -w /work/starter cs4220-net
python3 experiments.py

The challenge client needs the class server: run it on your own machine, or in the container without --network none. We host no local peer.

Tool references

• Python socket module
• ip-netns
• tc-netem
• Course container help and docker run