Content-addressable network

The content-addressable network (CAN) is a distributed, decentralized P2P infrastructure that provides hash table functionality on an Internet-like scale. CAN was one of the original four distributed hash table proposals, introduced concurrently with Chord, Pastry, and Tapestry. Like other distributed hash tables, CAN is designed to be scalable, fault tolerant, and self-organizing. The architectural design is a virtual multi-dimensional Cartesian coordinate space, a type of overlay network, on a multi-torus. This n-dimensional coordinate space is a virtual logical address, completely independent of the physical location and physical connectivity of the nodes. Points within the space are identified with coordinates. The entire coordinate space is dynamically partitioned among all the nodes in the system such that every node possesses at least one distinct zone within the overall space. A CAN node maintains a routing table that holds the IP address and virtual coordinate zone of each of its neighbors. A node routes a message towards a destination point in the coordinate space. The node first determines which neighboring zone is closest to the destination point, and then looks up that zone's node's IP address via the routing table. To join a CAN, a joining node must: Find a node already in the overlay network. Identify a zone that can be split Update the routing tables of nodes neighboring the newly split zone. To find a node already in the overlay network, bootstrapping nodes may be used to inform the joining node of IP addresses of nodes currently in the overlay network. After the joining node receives an IP address of a node already in the CAN, it can attempt to identify a zone for itself. The joining node randomly picks a point in the coordinate space and sends a join request, directed to the random point, to one of the received IP addresses. The nodes already in the overlay network route the join request to the correct device via their zone-to-IP routing tables.