Where would a Distributed Hash Table be used in place of BitTorrent?

Question

The lack of recent research into the field of DHTs in comparison to BitTorrent (Tribler being the most significant research project) has lead me to wonder about the usage of DHTs.

Both BitTorrent and Distributed Hash Tables provide a method for distributing content among peers using a key-value like datastore. What are the use cases where a DHT would be more applicable than using BitTorrent?

Answer 1

BitTorrent and most file sharing applications are built on unstructured peer-to-peer overlay networks.

A DHT is a structured peer-to-peer network overlay.

Structured and unstructured peer to peer networks differ mainly in their routing algorithms. Unstructured P2P networks rely on flooding or heuristic searches. Searches aren't necessarily guaranteed to find a file that its looking for.

Whereas with a DHT (structured P2P network), barring a network error or some abnormality, it is guaranteed a file stored under a given key will be found on request. (I've done a lot of performance testing with free pastry and its extremely reliable)

A DHT would be more suitable to applications where the file stored in the P2P network MUST be found. With BitTorrent, I guess it's not essential that each file is found by every request.