Distributed hash table: Difference between revisions

Revision as of 14:13, 3 February 2024

Revision as of 05:34, 4 February 2024

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Gnutella and similar networks moved to a [[query flooding]] model{{spaced ndash}} in essence, each search would result in a message being broadcast to every other machine in the network. While avoiding a [[single point of failure]], this method was significantly less efficient than Napster. Later versions of Gnutella clients moved to a [[dynamic querying]] model which vastly improved efficiency.<ref>{{cite journal |last1=Richter, Stevenson|display-authors=et al |title=Analysis of the impact of dynamic querying models on client-server relationships |journal=Trends in Modern Computing |date=2009 |pages=682–701}}</ref>

Freenet is fully distributed, but employs a [[Heuristic (computer science)|heuristic]] [[key-based routing]] in which each file is associated with a key, and files with similar keys tend to cluster on a similar set of nodes. Queries are likely to be routed through the network to such a cluster without needing to visit many peers.<ref>{{citation |url=https://freenetproject.org/papers/lic.pdf |title=Searching in a Small World Chapters 1 & 2 |access-date=2012-01-10 |archive-date=2012-03-16 |archive-url=https://web.archive.org/web/20120316102141/https://freenetproject.org/papers/lic.pdf |url-status=dead }}</ref> However, Freenet does not guarantee that data will be found.

Distributed hash tables use a more structured key-based routing in order to attain both the decentralization of Freenet and Gnutella, and the efficiency and guaranteed results of Napster. One drawback is that, like Freenet, DHTs only directly support exact-match search, rather than keyword search, although Freenet's [[routing algorithm]] can be generalized to any key type where a closeness operation can be defined.<ref>{{citation |chapter-url=https://freenetproject.org/papers/ddisrs.pdf |title=A Distributed Decentralized Information Storage and Retrieval System |chapter=Section 5.2.2 |access-date=2012-01-10 |archive-date=2012-03-16 |archive-url=https://web.archive.org/web/20120316102156/https://freenetproject.org/papers/ddisrs.pdf |url-status=dead }}</ref>

In 2001, four systems&mdash;[[Content addressable network|CAN]],<ref name = "Ratnasamy01">{{cite journal |title=A Scalable Content-Addressable Network |publisher=In Proceedings of ACM SIGCOMM 2001 |author=Ratnasamy |year=2001 |url=http://www.eecs.berkeley.edu/~sylvia/papers/cans.pdf |access-date=2013-05-20|display-authors=etal}}</ref> [[Chord (peer-to-peer)|Chord]],<ref>[[Hari Balakrishnan]], [[M. Frans Kaashoek]], David Karger, [[Robert Tappan Morris|Robert Morris]], and Ion Stoica. [http://www.cs.berkeley.edu/~istoica/papers/2003/cacm03.pdf Looking up data in P2P systems]. In [[Communications of the ACM]], February 2003.</ref> [[Pastry (DHT)|Pastry]], and [[Tapestry (DHT)|Tapestry]]&mdash;ignited DHTs as a popular research topic.

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* [[Oracle Coherence]]: an in-memory data grid built on top of a Java DHT implementation

* [[Perfect Dark (P2P)|Perfect Dark]]: a [[peer-to-peer]] [[file-sharing]] application from Japan

* [[Retroshare]]: a [[Friend-to-friend]] network<ref>[http://retroshare.sourceforge.net/wiki/index.php/Frequently_Asked_Questions#4-1_How_does_RetroShare_know_my_friend.27s_IP_address_and_port.3F_Why_don.27t_I_need_a_static_IP_address.3F_What_is_DHT_for.3F Retroshare FAQ] {{Webarchive|url=https://web.archive.org/web/20130717094704/http://retroshare.sourceforge.net/wiki/index.php/Frequently_Asked_Questions#4-1_How_does_RetroShare_know_my_friend.27s_IP_address_and_port.3F_Why_don.27t_I_need_a_static_IP_address.3F_What_is_DHT_for.3F |date=2013-07-17 }} retrieved December 2011</ref>

* [[Jami (software)|Jami]]: a privacy-preserving voice, video and chat communication platform, based on a Kademlia-like DHT

* [[Tox (protocol)|Tox]]: an [[instant messaging]] system intended to function as a [[Skype]] replacement