1 / 19

Bandwidth Allocation in Peer-to-Peer File Sharing Networks

This study focuses on the allocation of bandwidth in peer-to-peer file sharing networks, examining the incentives for peers to contribute and the interactions between sharers and freeriders. The paper presents a network model and formula for analyzing the equilibrium networks and characterizing resource provision by peers. It also discusses the economics literature on P2P file sharing networks and the role of congestion.

smallwood
Download Presentation

Bandwidth Allocation in Peer-to-Peer File Sharing Networks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bandwidth Allocation inPeer-to-Peer File Sharing Networks Albert Creus-Mir Ramon Casadesus-Masanell Andres Hervas-Drane

  2. Ramon Albert

  3. Outline Motivation Previous literature Bandwidth allocation Network model Formula, approximation and properties Equilibrium networks Utilities and timing Characterizing resource provision by peers

  4. Economics literature on P2P file sharing networks Network supported by social preferences: • Golle, P. and Leyton-Brown, K. and Mironov, I. and Lillibridge, M. (2001) • Antoniadis, P. and Courcoubetis, C. and Mason, R. (2004) • Cunningham, B. M. and Alexander, P. J. and Adilov, N. (2004) • Feldman, M. and Papadimitriou, C. and Chuang, J. and Stoica, I. (2004) Introduce role of congestion: • Asvanund, A. and Clay, K. and Krishnan, R. and Smith, M. D. (2004) • Krishnan, R. and Smith, M. D. and Tang, Z. and Telang, R. (2004) Our contribution: • First model on incentives to contribute presenting network foundation • First model to study interactions

  5. Setup: • There are S sharers and F freeriders out of a total N peers (S+F=N) • (To share or to freeride is a decision – more on this later) • Resources: • Each peer has valuable content available (non-rival resource) • Each peer has one unit of upload bandwidth available (rival resource), download bandwidth is not a limiting factor • Connectivity: • Each peer connects to one sharer (to download content) • Upload bandwidth is allocated equably amongst peers connected Network foundation F1 1/2 Example network allocation for S=2 & N=3 1 S1 S2 1/2

  6. Stable network allocation A network allocation is stable if no peer can benefit from deviating to another sharer Unstable: Stable: 1/2 1/3 S1 S1 F1 F1 1 1 1/3 1/3 1/2 1 S2 S2 S3 S3 • Assumptions: • Only stable network allocations take place • Every stable network allocation is equiprobable • How is bandwidth distributed between sharers and freeriders?

  7. Example 1Stable network allocations for S=2 & N=3 F1 F1 S1 S2 S1 S2 Expected bandwidth of sharers = 0.75 Expected bandwidth of freeriders = 0.5 S / N = 0.66 Are sharers always better off than freeriders?

  8. Example 2Stable network allocations for S=2 & N=4 F2 F1 F2 F1 S1 S2 S1 S2 Expected bandwidth of sharers = 0.5 Expected bandwidth of freeriders = 0.5 S / N = 0.5 … not always!

  9. Example 3Stable network allocations for S=2 & N=5 F1 F2 F3 F1 F2 F3 F1 F2 F3 S1 S2 S1 S2 S1 S2 F1 F2 F3 F1 F2 F3 F1 F2 F3 S1 S2 S1 S2 S1 S2 Expected bandwidth of sharers = 0.416 Expected bandwidth of freeriders = 0.388 S / N = 0.4

  10. The general formula The expected bandwidth for sharers is given by where and We can simply derive by taking into account that

  11. Approximation: S/N Expected bandwidth for sharers compared to S/N (Differences are ‘augmented’ 10.000 times) The approximation makes sharing (slightly) less attractive…and makes freeriding (slightly) more attractive

  12. Further constrained sharers ade = – S/N Sharers cannot connect to themselves Alternative model: Sharers only connect to themselves

  13. Bandwidth as the scarce resource in P2P file sharing networks Bandwidth: units of content / time = S/N Maximum effective bandwidth is 1 N Congestion: time / units of content = N/S When S=N, it takes one unit of time to download a unit of content Normalization: θ= Technology parameter θ / (S/N)= Congestion (time) td = θ (N/S) N

  14. Utilities and timing Freeriders Sharers Notation: Utility derived from content Cost of pertaining to P2P network Cost of sharing Impatience Time to download (congestion) Timing: 1. Peers decide to share or to freeride 2. Peers interconnect over the network and congestion is realized

  15. To share or not to share? 1. For a sharer not to wish to freeride we need: 2. For a freerider not to wish to share we need: 1 & 2 = Where ρi is the marginal sharer

  16. Equilibrium network configurations Characterize equilibria: The solution to the system given by G and H pins down the set of most patient sharers for all equilibrium network configurations Equilibrium property: Freeriders Sharers ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

  17. Example.Multiple equilibrium network configurations

  18. Equilibrium with For N large enough, a unique network equilibrium exists: Number of sharers: Utility of peers in the network: S* N N Full sharing range Partial sharing range Full sharing range Partial sharing range Sharing increases if Technology improvement creates value for all participants Negative network effects

  19. Asvanund et al. (2004): congestion worsens with network size

More Related