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Enhancing BitTorrent Protocol: A Peer-to-Peer Workshop for Client Modifications

This workshop focuses on leveraging the BitTorrent protocol to optimize download and upload efficiency, especially in regions with low upload capacities like Africa and China. Participants will create or modify their own BitTorrent clients using Python, allowing them to compare performance with standard clients while maintaining controlled upload rates. The process includes running a tracker and multiple clients concurrently on specific machines. Resources and guidelines will be provided to ensure smooth execution and testing of the modified clients while tracking their performance metrics.

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Enhancing BitTorrent Protocol: A Peer-to-Peer Workshop for Client Modifications

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  1. BitTorrent Framework

  2. Background • BT is a very popular peer to peer protocol with many implementations: • http://en.wikipedia.org/wiki/Comparison_of_BitTorrent_clients • The first one was created in Python by Bram Cohen.

  3. Workshop goal • Exploit BitTorrent protocol to give less for more. • Real world motivation • Places with low upload (Africa, China) • Bad character

  4. How do I test my idea • Create my own (or modified) BitTorrent client. • Run together: • “The World”: N “standard” BitTorrent Clients. • Specific upload rate • Various download stages • My Client • See how much time my client ran, and what was its upload / download ratio.

  5. Tracker BT BT BT BT BT BT BT BT BT BT BT Execution example run-all.sh

  6. How does it work? • Run tracker • Run the “world” • Run your client (if given)

  7. How does it work? • Both tracker and the “world” run on the same computer • we have • pc-hanoch-w1 • pc-hanoch-w2 • Please reserve time in: • http://0368350023.wikispaces.com/ • Or from course www - "Scheduling computers for tests."

  8. The main script - run_all.sh • Location: • /users/courses/hanochworkshop/bittorrent • Run_all.sh: • Parameters: • Start / stop • My client – optional

  9. run_all.sh operation • Start: • Create download directory • Run the “world” • Each world client starts with different “saved” amount. • Run “my client” – if given • All uploads rates are restricted. • Stop • Kill all python threads

  10. To run client separately: • BitTornado-My-Client/btdownloadheadless.py • --saveas /vol/scratch/bt-download/picture.tst.bmp • --max_upload_rate 70 • --security 0 • ./picture.pc-hanoch-w[1,2].bmp.torrent • Not necessarily on the same machine as the world.

  11. What implementation we use • The clients are a modified version based on an up to date version of Bram Python Client. • Modifications: • “World” clients • do not print as it would only make a mess • reincarnate after the finish to make a real world feel. • “My Client” template – kills all clients when finished • All clients – print total time

  12. Python • Very common script language • Intuitive and readable • References: • python.org :http://docs.python.org/reference/ • http://wiki.python.org/moin/BeginnersGuide/NonProgrammers • http://wiki.python.org/moin/BeginnersGuide/Programmers • The book "Think like a Computer Scientist in Python" has a very good reputation:

  13. My Client • We supply a default “My Client” which is like the “standard” one. • If you want you may replace it with any other implementation, with certain reservations: • Remember we compare to our client. • It does not count to download a faster client than our client and simply say it is faster. • Client should either limit it’s upload rate, or be able to work with trickle.

  14. Getting started • Run the environment • ssh pc-hanoch-w[1,2] • cd /users/courses/hanochworkshop/bittorrent • run_all.sh • start • [BitTornado-My-Client/btdownloadheadless.py] • Note tracker prints a message for each GET. • You can connect to the tracker with a browser at: • http://pc-hanoch-w1:6970/ • Do ls -l /vol/scratch/bt-download/ to see downloaded files

  15. What is it doing? • Run bttrack. • Copy From FreshFiles a set of “downloaded” files to download directory. • Run X seeds • Run a python client per “downloaded” file. • Run my client if given

  16. For debug: run client separately • ./run_all.sh start to start the world • BitTornado-My-Client/btdownloadheadless.py • --saveas /vol/scratch/bt-download/picture.tst.bmp • --max_upload_rate 70 • --security 0 • ./picture.pc-hanoch-w[1,2].bmp.torrent • Start debug. • Use your favorite debug environment. • IDLE is standard source level debugger.

  17. Directory Structure • BitTornado-My-Client – • high level application • BitTornado-My-Client/BitTornado – • services • BitTornado-My-Client/BitTornado/BT1 – • Actual work

  18. Client Operation • btdownloadheadless.py – First to run. • Performs initializations. • get_response – parse the .torrent • Infohash – the ID of the .torrent • startEngine – Start connection with peers • startRerequester - Start connection with tracker • Run rawserver.listen_forever from RawServer.py. • listen_forever is: • Polling port • executing func() from a task queue.

  19. Receiving messages • From listen_forever loop it goes to: • BT1/Connecter.py/got_message • CHOKE • UNCHOKE • INTERESTED • NOT_INTERESTED • BITFIELD • REQUEST • CANCEL • PIECE • HAVE

  20. Influencing decisions • Can be done in in one of the callbacks which spring from Connecter.py / got_message: • Downloader.py • HAVE->got_have->send_interested • maybe check connection before sending?

  21. BT tracker • Send GET request in Rerequester.py / announce • Receive GET data in thread in Rerequester.py / _rerequest

  22. Influencing decisions • In Encrypter.py / start_connection or _start_connection_from_queue For instance try different max_connections. _rerequest_single – check timout for scheduling.

  23. Policy • Choker.py/_round_robin – decide who to choke / optimistically un choke / send_have to. • Downloader.py / _request_more. • PiecePicker.py / next - rarest piece, etc. • got_unchoke->_request_more->next…

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