A Peer-to-Peer Simulator

Slide 1: Introduction Model Simulation Application Summary A Peer-to-Peer Simulator Uwe Schmidt Bachelor Thesis August 17, 2006 Uwe Schmidt: A Peer-to-Peer Simulator 1 / 28

Slide 2: Introduction Model Simulation Application Summary Outline Introduction 1 Model 2 Simulation 3 Application 4 Uwe Schmidt: A Peer-to-Peer Simulator 2 / 28

Slide 3: Introduction Model Simulation Application Summary Outline Introduction 1 Model 2 Simulation 3 Application 4 Uwe Schmidt: A Peer-to-Peer Simulator 3 / 28

Slide 4: Introduction Model Simulation Application Summary Peer-to-Peer File-Sharing Gaining Importance Less expensive in comparison to dedicated file servers Exploit bandwidth of users Resilient to flashcrowds BitTorrent Files are separated into chunks Popular (also for legal purposes) Microsoft Avalanche Uses network coding for chunk distribution Uwe Schmidt: A Peer-to-Peer Simulator 4 / 28

Slide 5: Introduction Model Simulation Application Summary Motivation Freeriding Common problem of all P2P systems Large fraction of peers are free-riders BitTorrent tries to restrain it by enforcing a tit-for-tat strategy Primary purpose of the simulator: Research the impact of the amount of free-riders on ... Download times Peer load Uwe Schmidt: A Peer-to-Peer Simulator 5 / 28

Slide 6: Introduction Model Simulation Application Summary Outline Introduction 1 Model 2 Simulation 3 Application 4 Uwe Schmidt: A Peer-to-Peer Simulator 6 / 28

Slide 7: Introduction Model Simulation Application Summary General Similar to BitTorrent (chunk-based file-sharing) Global knowledge of all other peers in the system No incentives to upload are given (such as tit-for-tat) Peers wait random time between downloads Peer Chunk Selection Download Behavior File Multiple Downloads Chunk#1 Chunk#2 ... Chunk#n Peer Selection Queued Requests Peer Lists for Chunks Chunk Selection Peer#13 Peer#11 Peer Selection Peer#6 Peer#2 List List List Peer#5 Peer#40 Peer#77 Peer#8 Peer#19 Uwe Schmidt: A Peer-to-Peer Simulator 7 / 28

Slide 8: Introduction Model Simulation Application Summary General Configuration GUI Uwe Schmidt: A Peer-to-Peer Simulator 8 / 28

Slide 9: Introduction Model Simulation Application Summary Peers Separated into peer groups: Peer Group Number of members Number of free-riders Bandwidth (upstream & downstream) Maximum number of simultaneous uploads & downloads Disconnect probability after successful file download Uwe Schmidt: A Peer-to-Peer Simulator 9 / 28

Slide 10: Introduction Model Simulation Application Summary Peers Configuration GUI Uwe Schmidt: A Peer-to-Peer Simulator 10 / 28

Slide 11: Introduction Model Simulation Application Summary Files Separated into file types: File Type Number of files Number of copies (per file) File size (determines number of chunks) File distribution to peer groups Popularity distribution of files among type Global Chunk Size Applies to all file types Uwe Schmidt: A Peer-to-Peer Simulator 11 / 28

Slide 12: Introduction Model Simulation Application Summary Files Configuration GUI Uwe Schmidt: A Peer-to-Peer Simulator 12 / 28

Slide 13: Introduction Model Simulation Application Summary Requests Mean request period Request distribution to file types Uwe Schmidt: A Peer-to-Peer Simulator 13 / 28

Slide 14: Introduction Model Simulation Application Summary Requests Configuration GUI Uwe Schmidt: A Peer-to-Peer Simulator 14 / 28

Slide 15: Introduction Model Simulation Application Summary Outline Introduction 1 Model 2 Simulation 3 Application 4 Uwe Schmidt: A Peer-to-Peer Simulator 15 / 28

Slide 16: Introduction Model Simulation Application Summary Preliminaries Factories Create peers and files Deploy files to peers File Request Generator Uses request configuration and file popularity settings Creates empirical distributions for file indexes Replays this distributions during the simulation Uwe Schmidt: A Peer-to-Peer Simulator 16 / 28

Slide 17: Introduction Model Simulation Application Summary Discrete Event Simulation Concept Ordered Event List Simulation Executive removes executes Next Event inserted changes state appends data Entities schedule append data New Events Data Collection Uwe Schmidt: A Peer-to-Peer Simulator 17 / 28

Slide 18: Introduction Model Simulation Application Summary Simulation Cycle File Request Generator Peer Download Part Upload Part Download File Incoming Chunk Request Add Chunks to More Uploads Download Complete Download Queue possible? yes no Last Chunk Process Download Queue Upload Chunk Queue Chunk Request no of File? yes More Downloads Maybe Chunk Download started Chunk Request Queued Upload Complete Update Uploads possible? go Ofline yes no Maybe start Select Chunk Update Downloads Process Upload Queue new Request Select Peer Download Chunk Uwe Schmidt: A Peer-to-Peer Simulator 18 / 28

Slide 19: Introduction Model Simulation Application Summary Control Uwe Schmidt: A Peer-to-Peer Simulator 19 / 28

Slide 20: Introduction Model Simulation Application Summary Collected Data Before the Simulation Peer groups File types List of files with chunk mapping List of peers with file mapping During the Simulation Completed chunk transfers Completed file downloads Miscellaneous (e.g. peer goes offline) After the Simulation List of peers with file mapping Uwe Schmidt: A Peer-to-Peer Simulator 20 / 28

Slide 21: Introduction Model Simulation Application Summary Outline Introduction 1 Model 2 Simulation 3 Application 4 Uwe Schmidt: A Peer-to-Peer Simulator 21 / 28

Slide 22: Introduction Model Simulation Application Summary Overview Written in Java SE 5 Used Eclipse 3 58 classes in 8 packages ≈ 8000 lines of code and comments (JavaDoc) Used Libraries Jakarta Commons Math → Random Number Generators Jakarta Commons Configuration → XML Configuration JFreeChart → Charts Uwe Schmidt: A Peer-to-Peer Simulator 22 / 28

Slide 23: Introduction Model Simulation Application Summary Structure User starts starts Graphical User Interface Console Mode controls controls Simulator changes uses executes File Request Generator Factories Next Event uses uses use create create writes controls returns Files Configuration Files Peers to download save load uses use consist of transfer use schedule write removes Config File Chunks Strategies New Events Log Files use inserted Random Number Generators Event List Uwe Schmidt: A Peer-to-Peer Simulator 23 / 28

Slide 24: Introduction Model Simulation Application Summary Used Design Patterns Observer Pattern Simulator → Simulation State & Progress Configuration → Changes Singleton Pattern Implemented by frequently used components Single point of access from everywhere No need to pass references on to other components Command Pattern Hashtable that maps an ActionString to a Command Avoid code duplication Uwe Schmidt: A Peer-to-Peer Simulator 24 / 28

Slide 25: Introduction Model Simulation Application Summary Extensions General modular design Selection strategies are easy to change and extend Example (Chunk Selection) Select rarest chunk among 50 randomly selected ones to reflect that peers have no global knowledge in reality Example (Peer Selection) Select peer with most upstream left Select peer with smallest upload queue (if all are busy) Uwe Schmidt: A Peer-to-Peer Simulator 25 / 28

Slide 26: Introduction Model Simulation Application Summary Demo Uwe Schmidt: A Peer-to-Peer Simulator 26 / 28

Slide 27: Introduction Model Simulation Application Summary Summary Easy and flexible way to simulate P2P systems (similar to BitTorrent) Tool to research the impact of free-riders, and other parameters, on a P2P system Modular designed and extendable Uwe Schmidt: A Peer-to-Peer Simulator 27 / 28

Slide 28: Thank you for your attention Questions? Uwe Schmidt: A Peer-to-Peer Simulator 28 / 28