View source for Coral Content Distribution Network

The '''Coral Content Distribution Network''', sometimes called '''Coral Cache''' or '''Coral''', was a [[Free software|free]] [[peer-to-peer]] [[content distribution network]] that ran from 2004 until 2015. It was designed and operated by Michael Freedman. Coral used the [[Bandwidth (computing)|bandwidth]] of a worldwide network of web proxies and name servers to mirror [[World Wide Web]] content, often to avoid the [[Slashdot Effect]] or to reduce the load on web servers.

== Operation ==

Coral avoided high loads on individual nodes through an indexing abstraction called a [[distributed sloppy hash table]] (DSHT); DSHTs create self-organizing clusters of [[Node (networking)|nodes]] which fetch information from each other to avoid communicating with more distant or heavily-loaded servers.

The ''sloppy'' hash table refers to the fact that Coral was made up of concentric rings of [[distributed hash table]]s (DHTs), each ring representing a wider and wider geographic range (or rather, [[Ping (networking utility)|ping]] range). The DHTs are composed of nodes all within some latency of each other (for example, a ring of nodes within 20 [[millisecond]]s of each other). It avoids hot spots (the 'sloppy' part) by only continuing to query progressively larger sized rings if they are not overburdened. In other words, if the two top-most rings are experiencing too much traffic, a node will just ping closer ones: when a node that is overloaded is reached, upward progression stops. This minimises the occurrence of hot spots, with the disadvantage that knowledge of the system as a whole is reduced.

== Usage ==

Coral users could access content through the Coral Cache by adding &lt;code&gt;.nyud.net&lt;/code&gt; to the [[hostname]] in the site's [[Uniform Resource Locator|URL]], resulting in what is known as a 'coralized link'. So, for example,
:&lt;code&gt;&lt;nowiki&gt;http://example.com&lt;/nowiki&gt;&lt;/code&gt;
becomes
:&lt;code&gt;&lt;nowiki&gt;http://example.com.nyud.net&lt;/nowiki&gt;&lt;/code&gt;
Any additional address component after the hostname remains after &lt;code&gt;.nyud.net&lt;/code&gt;; hence
:&lt;code&gt;&lt;nowiki&gt;http://example.com/folder/page.html&lt;/nowiki&gt;&lt;/code&gt;
becomes
:&lt;code&gt;&lt;nowiki&gt;http://example.com.nyud.net/folder/page.html&lt;/nowiki&gt;&lt;/code&gt;
For websites that use a non-standard port, for example,
:&lt;code&gt;&lt;nowiki&gt;http://example.com:8080&lt;/nowiki&gt;&lt;/code&gt;
becomes
:&lt;code&gt;&lt;nowiki&gt;http://example.com.8080.nyud.net&lt;/nowiki&gt;&lt;/code&gt;

== History ==

The project was deployed in March 2004, during which it has been hosted on [[PlanetLab]], a large-scale distributed research network of several hundred servers deployed at universities worldwide. It has not, as originally intended, been deployed by third-party volunteer systems. About 300 to 400 PlanetLab servers were running CoralCDN. The [[source code]] is freely available under the terms of the [[GNU GPL]].

In August 2012 it was stated that active development had been "stopped for a while", although the CDN itself would continue to operate.&lt;ref name="overview" /&gt;

 &lt;code&gt;&lt;nowiki&gt;*.nyud.net&lt;/nowiki&gt;&lt;/code&gt; had stopped [[Domain Name System|resolving]], rendering the CDN non-functional. The project website is still up, but has not been updated since 2012.

== See also ==

* [[CoDeeN]]
* [[Globule (CDN)]]
* [[Content Delivery Network]]

==Source==

[http://wikipedia.org/ http://wikipedia.org/]
[[Category:Online services]]
[[Category:Data storage]]