implementation of chord

right now, we're thinking we implement chord (in python) and set it up so we can run it on mininet, then we run the simulations they describe in the paper on that network, and we implement one of the applications they run on top - in the paper, they describe large-scale distributed combinatorialsearch, so we could write a password cracking program that runs distributed on the chord network.

• src/: all source code
  • chord/: chord protocol module. intended to be consumed by applications.
    • node.py the main node class. this is what should be used in applications.
    • address.py simple class that contains addressing info for chord nodes.
    • net.py class that handles socket/network communication for chord.
• experiments/ various scripts for running chord on mininet
• tests/: test suites.
• setup/: scripts for verifying project is installed correctly
  • chk_config.py: simple script for verifying setup. if you get a mininet import error, this can help debug. make sure you can run it with sudo and/or pychord alias (see usage)
  • chk_mininet.py: simple script for making sure mininet works. sets up 2 hosts, 1 switch, and pings between them. make sure you can run it with sudo and/or pychord alias (see usage)
• .python-version: specifies python version for pyenv.
• chk_config.py: simple script for verifying setup. if you get a mininet import error, this can help debug. make sure you can run it with sudo and/or pychord alias (see usage)
• chk_mininet.py: simple script for making sure mininet works. sets up 2 hosts, 1 switch, and pings between them. make sure you can run it with sudo and/or pychord alias (see usage)
• chord_paper.pdf: the research paper we're working from.
• Final_Report_Networks.pdf: Final paper submitted for course.
• requirements.txt: python dependencies
• requirements-dev.txt: development dependencies. installs from requirements.txt first, then adds dev dependencies, so no need to run pip install for both.
• chord_paper.pdf: the research paper we're working from.

• mininet
• openvswitch-testcontroller
  • explanation: ovs-controller renamed to test-controller
• a recent python. we use 3.11, installed via pyenv.

We developed on an ubuntu instance on aws EC2.

1. ensure that mininet and testcontroller are installed and linked.

   • sudo apt install mininet
     • you can verify installation with mn --version, which will print the mininet version if correctly installed.
   • sudo apt-get install openvswitch-testcontroller
   • sudo ln /usr/bin/ovs-testcontroller /usr/bin/controller

2. get the path to mininet module (run with system python). remember/copy&paste this for later.

   • python3 -c "import mininet; print(mininet.__file__)"
   • this should print something like /usr/lib/python3/dist-packages/mininet/__init__.py

3. add this path (up to and not including mininet/) to your PYTHONPATH env variable: export PYTHONPATH=$PYTHONPATH:/usr/lib/python3/dist-packages/

   • to have this persist, add to your shell config file (.bashrc, etc)

4. install pyenv (recommended), or install python directly (make sure you can use pip)

   • if using pyenv, use the basic install for linux. Once installed, you'll also need to install python 3.11 to match our version. pyenv will automatically pick up the .python-version file in this repo.
     • pyenv install 3.11

5. clone this repo. from inside the repo, create and activate a virtual environment:

   • python -m venv [.venv | venv | ...]
   • source .venv/bin/activate

6. now run python -c "import mininet; print(mininet.__file__)" again. this should output the same path as when running with system python.

7. install dependencies:

   • pip install --upgrade pip
   • to work on this: pip install -r requirements-dev.txt
   • to just run: pip install -r requirements.txt At this point, you should be installed and good to go.

We know there's a lot of weird steps to this. There are two scripts that can help make sure things are set up correctly (see usage for how to invoke them):

1. setup/chk_config.py will make sure your PYTHONPATH is correct, and that you can interact with mininet from python scripts.
2. setup/chk_mininet.py will make sure that you can set up and run a network with mininet. If you see "2 packets transmitted, 2 received, 0% packet loss", then it's working correctly.

To run scripts using mininet, the full command format is:

• sudo [pass PYTHONPATH up] [path/to/venv/python] some_script.py Your path depends on where you clone this repo. So to run the "check config" script, the command will look like:
• sudo PYTHONPATH=$PYTHONPATH /home/ubuntu/chord/.venv/bin/python setup/chk_config.py For quality of life, add an alias to your shell config:
• alias pychord="sudo PYTHONPATH=\$PYTHONPATH /home/ubuntu/chord/.venv/bin/python " That way checking config will be:
• pychord setup/chk_config.py

explanation: running python programs is a little weird, since we're using system-installed mininet with python in a virtual env (we'd avoid this by not using a venv, but system python doesn't seem to be compatible with pip). mininet needs root privileges, but sudo doesn't inherit env variables by default. to invoke, we need to pass our PYTHONPATH to the root environment, and also use the full python path (to the venv python, otherwise it will use system python).