2-hop torrentsmell a distributed tracking algorithm name:raynor vliegendhart date:july 10, 2009...
DESCRIPTION
Central Tracker 3 Request PeerlistTRANSCRIPT
2-Hop TorrentSmellA distributed tracking algorithm
name: Raynor Vliegendhartdate: July 10, 2009event: Tribler Dev Meeting
Research Question
How to decentralizePeer Discovery Functionality
with hooks forSecurityand Scalability?
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Central Tracker
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Download SwarmCentral TrackerYou
Request
Peerlist
Central Tracker
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Peer List
Download SwarmCentral TrackerYou
Download SwarmCentral TrackerYou
Central Tracker
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Connect to Download Swarm
Central Tracker
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Keep in touch with tracker to
1.discover newpeers;
2.announceyour presence.
Download SwarmCentral Tracker
Distributed Tracking
How do we…
• track peers in the swarm?
• find the distributed trackerstracking the swarm?
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Distributed Tracking Algorithm
How do we…
• track peers in the swarm? RePEX• find the distributed trackers
tracking the swarm? Extended
Remote Content Search
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2-HopTorrentSmell
Peer Exchange
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Modern BitTorrent clients can exchange their neighbourhood sets throughPeer Exchange (PEX)
136.12.5.59
8.33.232.4
65.1.5.212
Peer Exchange
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Modern BitTorrent clients can exchange their neighbourhood sets throughPeer Exchange (PEX)
136.12.5.59
136.12.5.59
8.33.232.4
65.1.5.212
Peer Exchange
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Modern BitTorrent clients can exchange their neighbourhood sets throughPeer Exchange (PEX)
136.12.5.59
8.33.232.4
65.1.5.212
65.1.5.212, 8.33.232.4
RePEX
• Reconnect to PEX peers encountered before.• Discover new and reliable peers.
Goal:Each peer has a local list of peers in the swarm.
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• Which swarms to track?
• How often? How many peers to store?
RePEX Research Questions
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• 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.
RePEX Research Questions
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Remote Content SearchCurrently implemented
in Tribler:
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“Obama”
“Obama”
“Obama”
Remote Content Search
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obama.mp3 SHA1
obama.avi SHA1
X
Tribler peers respond with matching torrent files
Extended Remote Content Search+ RePEX
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“Obama”
“Obama”
“Obama”
RePEX Tribler Peer
Extended Remote Content Search+ RePEX
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RePEX Tribler Peer
obama.mp3 SHA1
obama.avi SHA1
X
+136.12.5.59, 8.33.232.4, …
A RePEX peer includes swarm peers in the response
2-Hop TorrentSmell
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• Tribler peers already announce their download profile through BuddyCast
• We can use this to further extendRemote Content Search
2-Hop TorrentSmell
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“Obama”
212.13.153.124
The user issues a query as normally
2-Hop TorrentSmell
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212.13.153.124
The responding Tribler peer knows who has downloaded obama.avi
obama.avi SHA1+RePEX: 212.13.153.124, …
2-Hop TorrentSmell
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212.13.153.124
So the user can reissue the query to that peer
“Obama”
2-Hop TorrentSmell
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212.13.153.124
Finally, the RePEX peer responds with a list of swarm peers
obama.avi SHA1+Swarm: 136.12.5.59, 8.33.232.4, …
Algorithm Summary
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• 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…
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Additional Research Questions
But also:
• Do peers lie about PEX capabilities?
• What’s the PEX “response time”of non-Tribler peers?
• <your input…?>
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