Digging Into KAD Users’ Shared Folders

Characterizing peer-to-peer overlays is crucial for understanding their impact on service provider networks and assessing their performance. Most popular file exchange applications use distributed hash tables (DHTs) as a framework for managing information. Their fully decentralized nature makes monitoring and users tracking challenging. In this work, we analyze KAD, a widely deployed DHT system. Thanks to the unique possibility to monitor a large population of about 20,000 ADSL clients at the edge of the network, we are able to characterize the content downloaded and shared by local users. We devised a passive content monitoring toolkit to reliably track users between sessions despite dynamic IP allocation. We applied our tool over one month of data. Our main findings are: (i) Over half a TB of fresh data is downloaded every day by the users we monitor, (ii) A significant fraction of peers (20%) regulary change their ID in the KAD overlay, either on a session basis or on a sub-session basis, which can be detrimental to the proper functioning of the DHT, (iii) Those users, that we term Chameleon users, are connected longer than regular users, and they (claim to) have less data in their shared folder than regular peers and (iv) As a consequence, even a non biased observation of the users shared folder can only provide a lower bound of the content downloaded and shared by a population of ADSL users.