Incentives: Difference between revisions

From
Jump to navigation Jump to search
Line 14: Line 14:


== EigenTrust ==
== EigenTrust ==

EigenTrust is an incentive system based on the traffic history of each peer. Uploading data to peer A increases the reputation of peer B from peer A's perspective. The reputation between all peers can be pictured using a trustmatrix <math>M</math> with elements <math>c_{i,j}</math>.
{| style="float:center; background:transparent; padding:0px; margin:0px;"
{| style="float:center; background:transparent; padding:0px; margin:0px;"
|[[Image:trustmatrix.jpg|thumb|center|300px|Networktraffic mapped to a Trustmatrix]]
|[[Image:trustmatrix.jpg|thumb|center|300px|Networktraffic mapped to a Trustmatrix]]

Revision as of 07:23, 26 July 2007

Problem

File-sharing networks like KaZaA and Gnutella have popularized the peer-to-peer (P2P) resource sharing model. Based on the altruistic behaviour of its users, principles of P2P systems sometimes conflict user's rational individuality. The individual's utility function is also influenced by negative factors like e.g. upload costs, limited upload bandwidth, enviousness or egoism. Hence some users use P2P networks without sharing own resources (free-riding).

Incentive systems

Point incentive system

Simple point incentive mechanisms as in e.g. the Maze-network don't prevent users from cheating. Two kinds of user collusion are observed.

  • Pair-wise collusion
Two users mutually exchange large amounts of data to increase their points. This kind of collusion profits from the rule that uploading earns more points that downloading consumes.
  • Spam account collusion
A user registers a number of spam-accounts to download from his main-account. Thus he transfers initial points given to new accounts to his main-account.

EigenTrust

EigenTrust is an incentive system based on the traffic history of each peer. Uploading data to peer A increases the reputation of peer B from peer A's perspective. The reputation between all peers can be pictured using a trustmatrix with elements .

Networktraffic mapped to a Trustmatrix

Tit-for-Tat

coming soon

Multi-Trust-Incentives