Review of Free Riding on Gnutella Eytan Adar and Bernardo Huberman Shreeram Sahasrabudhe

Jargon Gnutella -Protocol created by nullsoft guys (Winamp), network followed -Decentralized and Peer- to-Peer -Anonymity maintained -Limewire, Morpheus etc. use this protocol Free Riding 1> Peers that only download files without ever providing files for others 2> Peers providing files but not contributing to the desirable content on the network

What it [paper] speaks? Presents an extensive experimental analysis to illustrate and caution us about the effects of free riding in the Gnutella Network. Argues that Free Riding leads to –System Degradation –Adds Vulnerability to the system First proves that Free Riding does occur Gives three hypothesis (confirms by experiments) 1. A significant portion of Gnutella peers are free riders 2. Free riders are distributed evenly across different domains (and by bandwidth) 3. Peers that provide files for download are not necessarily those from which files are downloaded

Experiment Setup –Java based Furi client [Fu00] (A Gnutella Client) was modified to log messages flowing through. –Executed for 24hr period –Logged the ping (are you there?), pong (IP, port, # of files shared and the total size) and Query Response Messages (IP, port, ClientID, other location info) –Also considers effects NAT based peers some of which can report the same address. –33,335 hosts sharing 3,100,464 files, 87,668 query response messages

Experiment 1 (Free Riding) Approximately 69% (inc NAT based peers) of the peers share no files and 73% share ten or less files. Top 1% represent approximately 37 percent of the total files shared. This quickly escalates to the top 20% sharing 98% of the files. 63% of those sharing files never provided a query response. Again top 1% provides 47% answers. Sorted by the number of files they offer Hosts providing NO files

Experiment 2 (Free Distribution) Domains can function as a proxy for bandwidth Filtered the test set to 26,014 peers with IP  hostnames Peer count linearly related to files shared Even distribution of free riders TLD (top-level domain e.g (edu, net, org..)

Concentrated queries on particular topics Number of queries answered is not necessarily proportional to the number of files offered. Experiment 3 (“quality” vs. quantity)

Effect(s) Network – Two Factors Cause: Ultimately few individuals will contribute anything that is new and high quality. (The Tragedy of the Digital Commons) Solutions: Uploading files Peers participating actively in the protocol  Search Horizon Increases - Hosts can become unreachable  Saturation - Peers have limited number of connections Vulnerability The few providers begin to appear as a centralized server consisting of several peers. Prosecuting Agencies like RIAA can target top-serving peers Loss of anonymity Collapse

Solution - Free Riding FreeNet –Forces caching of downloaded files Users must know -> Identifiers for files Can replicate harmful / illegal data and taint hosts Napster –Defaults download directory to be the upload directory Spawn – buy & sell; public  private Usenet - Reduce the personal storage and BW cost