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2-Hop TorrentSmell A distributed tracking algorithm. name: Raynor Vliegendhart date: July 10, 2009 event: Tribler Dev Meeting. Research Question. How to decentralize Peer Discovery Functionality with hooks for Security and Scalability?. Central Tracker. Request Peerlist.
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2-Hop TorrentSmellA distributed tracking algorithm name: Raynor Vliegendhartdate: July 10, 2009event: Tribler Dev Meeting
Research Question • How to decentralizePeer Discovery Functionality • with hooks for • Security • and Scalability?
Central Tracker Request Peerlist
Central Tracker Peer List
Central Tracker Connect to Download Swarm
Central Tracker • Keep in touch with tracker to • discover newpeers; • announceyour presence.
Distributed Tracking • How do we… • track peers in the swarm? • find the distributed trackerstracking the swarm?
Distributed Tracking Algorithm • How do we… • track peers in the swarm? • RePEX • find the distributed trackerstracking the swarm? • ExtendedRemote Content Search 2-Hop TorrentSmell
Peer Exchange • Modern BitTorrent clients can exchange their neighbourhood sets throughPeer Exchange (PEX) 65.1.5.212 8.33.232.4 136.12.5.59
Peer Exchange • Modern BitTorrent clients can exchange their neighbourhood sets throughPeer Exchange (PEX) 65.1.5.212 136.12.5.59 8.33.232.4 136.12.5.59
Peer Exchange • Modern BitTorrent clients can exchange their neighbourhood sets throughPeer Exchange (PEX) 65.1.5.212 65.1.5.212, 8.33.232.4 8.33.232.4 136.12.5.59
RePEX • Reconnect to PEX peers encountered before. • Discover new and reliable peers. • Goal: • Each peer has a local list of peers in the swarm.
RePEX Research Questions • Which swarms to track? • How often? How many peers to store?
RePEX Research Questions • Which swarms to track? • Last 25 downloads, since we have been • in those swarms before • How often? How many peers to store? • Yet unknown; • Measurements needed to determine churn, online status, connectivity, etc.
Remote Content Search • Currently implementedin Tribler: “Obama” “Obama” “Obama”
Remote Content Search • Tribler peers respond with matching torrent files obama.mp3 SHA1 obama.avi SHA1 X
Extended Remote Content Search+ RePEX “Obama” “Obama” RePEX Tribler Peer “Obama”
Extended Remote Content Search+ RePEX • A RePEX peer includes swarm peers in the response obama.mp3 SHA1 obama.avi SHA1 +136.12.5.59, 8.33.232.4, … RePEX Tribler Peer X
2-Hop TorrentSmell • Tribler peers already announce their download profile through BuddyCast • We can use this to further extendRemote Content Search
2-Hop TorrentSmell • The user issues a query as normally “Obama” 212.13.153.124
2-Hop TorrentSmell • The responding Tribler peer knows who has downloaded obama.avi obama.avi SHA1 +RePEX: 212.13.153.124, … 212.13.153.124
2-Hop TorrentSmell • So the user can reissue the query to that peer “Obama” 212.13.153.124
2-Hop TorrentSmell • Finally, the RePEX peer responds with a list of swarm peers obama.avi SHA1 +Swarm: 136.12.5.59, 8.33.232.4, … 212.13.153.124
Algorithm Summary • 2 Hops needed using Extended RCS • RePEX used for tracking
Research Questions Recap • How often do we have to revisit swarms? • How many peers should we store per swarm? • What’s the churn rate? • Etc…
Additional Research Questions • But also: • Do peers lie about PEX capabilities? • What’s the PEX “response time”of non-Tribler peers? • <your input…?>