peer to peer workshop
DESCRIPTION
Peer to Peer Workshop. Understanding Peer Abandonment in BitTorrent networks. Introduction to BitTorrent. Introduction to BitTorrent. BitTorrent – Overview. Understanding Peer Abandonment. Challenges. The BitTorrent Protocol. Peer to Peer. Peer to Tracker. Tracker to Peer. - PowerPoint PPT PresentationTRANSCRIPT
Peer to Peer WorkshopUnderstanding Peer Abandonment in
BitTorrent networks
Introduction to BitTorrent
Introduction to BitTorrent
BitTorrent – Overview
Understanding Peer Abandonment
Abandonment – departure of a peer before completing the file download
Swarm size & Torrent
Size
Peer’s DL & Completion
rate
Challenges
Identify peer abandonment• How can we be sure that the peer has actually left?
Collect abandonment parameters• How can we know what’s the peer’s DL and completion
rate at abandonment?
Collect ‘enough’ information• How to collect enough information about abandonments
in the swarm for statistical purposes?
The BitTorrent Protocol
•Identify each other
Handshake•The pieces I hold
Bitfield
•I have a certain piece
Have
•I’m still here
Keep Alive
•An ID of the torrent
Info Hash•The client
stopped / completed
Stopped / Completed
Peer to Peer Peer to Tracker
Tracker to Peer
•A subset of peers from the swarm
Peers
What to do?
Client Tracker
Peer abandonment
An educated guess Using stopped event
Abandonment parameters
Conclude from events
Not in the protocol
Enough information
Connect to many peers
Who’ll use our tracker?
TIMCrawler ClientTorrent Impatience Monitor
Identify peer abandonment• Continuously try to reconnect to known non-seeders peers• ‘Play by the rules’
Collect abandonment parameters• Determine peer’s DL rate using the ‘Have’ frequency• Never become a seeder (to assure ‘Have’ msgs are sent)
Collect ‘enough’ information• Each test is a 24h run in a single swarm• Connect to many peers• Collect all data to a DB and analyze later
Results – Swarm size
up to 100 100-1000 1000 and over0%
2%
4%
6%
8%
10%
12%
14%1244 peers
3328 peers
16450 peers
Abandonment rate by number of seeders(total of 21022 peers)
Number of seeders
Aver
age
aban
donm
ent r
ate
Results – File size
<800MB 800MB-2GB >2GB4.8%
5.0%
5.2%
5.4%
5.6%
5.8%
6.0%
6.2%
5918 peers
8664 peers
6440 peers
Abandonment rate by file size(total of 21022 peers)
Torrent size
Aver
age
aban
donm
ent r
ate
Results – Completion rate
0-20 20-40 40-60 60-80 80-100
020406080
100120140160180200
Number of abandoners by completion rate(total of 536 peers)
Completion of torrent (%)
Num
ber o
f aba
ndon
ers
Results – Download rate0 10 20 30 40 50 60 70 80 90 100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
290
05
101520253035404550
Number of abandoners by download rate (total of 277 peers)
Estimated download rate (kB/s)
Num
ber o
f aba
ndon
ers
Conclusions
•Higher abandonment rate on small swarms
Swarm size
•Does not seem to affect abandonment
File size
•Most abandoners departure at the very beginningCompletion
rate
•Significant impact of DL rate on abandonmentDownload
rate