A Pssst, Over Here: Communicating Without Fixed Infrastructure

The Internet has increasingly moved from a system used to disseminate information to users from a relatively small number of content providers to a system that facilitates sharing information among users. This style can be plainly found in the most popular destinations and applications: Twitter, Facebook, Flickr, Skype, BitTorrent, one-click file sharing systems (e.g., RapidShare), etc. The shift from merely consuming information to sharing information has in fact led to several efforts to change the basic model of networking from host-based to content-based [Koponen et al. 2007; Jacobson et al. 2009] as this latter has become the basic mode of operations for users. That is, users fundamentally do not want to access some host in the network, but rather want to swap a given piece of information. The techniques explored in this work strive to transfer small amounts of information using a scheme that is not fundamentally host-centric. In a network model where information is generally disseminated upon request, we can readily build highly robust systems. A user interested in buying a book can easily find a book seller using a well-known DNS name (e.g., “amazon.com”). Further, server farms, content delivery networks, replicated DNS servers, geographically disparate replicas, multi-homed connectivity, etc. provide robustness of operation. We refer to this as the central hubmodel. Even if physically distributed, the service is orchestrated at some logically central location. This model makes perfect sense for certain activities (e.g., legitimate e-commerce). However, as noted above, users have evolved to become the most prolific content providers on the Internet. In technological terms this shift has manifested in one of two basic ways: (i) using a central hub to connect users and hold the shared content (e.g., Twitter) or (ii) using a central hub as a bootstrapping mechanism for direct peerto-peer information exchange (e.g., a BitTorrent tracker or, in the tracker-less variant, a site listing an existing DHT node). While the role of the central hub is reduced in the second approach, it is still required. Although a lightweight central hub may be perfectly reasonable in some cases, there may be other cases where such a central presence is undesirable, such as: