Structure
The structure of a DHT can be decomposed into several main components. The foundation is an abstract keyspace, such as the set of 160-bit strings. A keyspace partitioning scheme splits ownership of this keyspace among the participating nodes. An overlay network then connects the nodes, allowing them to find the owner of any given key in the keyspace.
Once these components are in place, a typical use of the DHT for storage and retrieval might proceed as follows. Suppose the keyspace is the set of 160-bit strings. To store a file with given and in the DHT, the SHA-1 hash of is generated, producing a 160-bit key, and a message is sent to any node participating in the DHT. The message is forwarded from node to node through the overlay network until it reaches the single node responsible for key as specified by the keyspace partitioning. That node then stores the key and the data. Any other client can then retrieve the contents of the file by again hashing to produce and asking any DHT node to find the data associated with with a message . The message will again be routed through the overlay to the node responsible for, which will reply with the stored .
The keyspace partitioning and overlay network components are described below with the goal of capturing the principal ideas common to most DHTs; many designs differ in the details.
Read more about this topic: Distributed Hash Table
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