Art-Net was invented by Artistic Licence, who hold the copyright. The protocol website is at: www.art-net.org.uk
Art-Net is a communication protocol developed to transport DMX512 and RDM lighting data over an Ethernet network. It used a simple UDP based packet structure designed to provide efficient and low overhead data flow.
It uses the concept of transporting 512 channel Universes of data so that conversion to and from DMX512 is trivial. Art-Net is often supported natively in dimmers and moving lights, so increasingly the DMX512 Universe is actually a virtual concept.
A total of 32,768 universe can be addressed. The protocol defines a Controller which is optimised for generating control data. It also defines a Node, which is optimised for converting to and from Art-Net data. A Node supports up to 4 logical inputs and four logical outputs; these are referred to as Input-Ports and Output-Ports.
The protocol specification is available for download from the Artistic Licence Engineering web site.
The following terminology is used by Art-Net:
A block of up to 512 channels of 8-bit intensity data capable of conversion to and from DMX512.
A block of 1024 Universes.
A piece of equipment that interfaces to Art-Net.
A device that is primarily designed to convert DMX512 to or from Art-Net. A Node supports up to 4 Input-Ports and 4 Output-Ports.
A device that is primarily designed to generate Art-Net, such as a lighting console.
One of the 32,768 possible addresses to which a Universe can be directed.
Art-Net specifies the direction of file transfer to be from a controller to a node during an upload. That is: a controller would upload new firmware to a node.
Art-Net specifies the direction of file transfer to be from a node to a controller during a download. That is: a controller would download a copy of a node’s configuration file in order to retrieve a local copy.
The first version of Art-Net, now called Art-Net I, was written in 1998 and released soon after. Art-Net I used broadcast data for all transactions including the streaming level data. The reason for the use of broadcast was simply to remove the need for any network configuration on the part of the user.
Art-Net I was implemented on 10BaseT networks and used for a relatively small quantity of universes – perhaps 10. This very modest level of bandwidth use worked well with a broadcast topology.
Art-Net I has an effective limit of approximately 40 Universes.
As the demand for channels grew, the broadcast topology became problematic. Broadcast data floods the entire network and appears at every node whether it needs it or not. Too much broadcast data overloads switches and nodes alike.
In order to address this problem, Art-Net II was released in 2006. At power on, the Art-Net II output of a console is identical to Art-Net I – all broadcast. However with Art-Net II, the console uses a simple algorithm to learn which nodes are consuming which Universes. It then switches to unicasting to the nodes. The reduction in network loading achieved with Art-Net II is massive, allowing Art-Net II networks to scale up to the bandwidth of the network.
Art-Net II has an effective limit of 256 Universes.
The need for ever more channels, driven by the expansion of pixel based systems, continues unabated. This led to the release of Art-Net 3 in 2011. Art-Net 3 increased the number of Universes that can be addressed from 8-bit to 15-bit. This removes the 256 universe limit of Art-Net II.