Architecture for Control Networks (ACN) is a suite of network protocols for theatrical control being developed by Entertainment Services and Technology Association (ESTA). The first official release is formally referred to as ANSI E1.17 - 2006 - Entertainment Technology - Architecture for Control Networks.
It may replace DMX as the control protocol for lighting systems and will be used for controlling more complex devices like video playback servers (media servers) and audio mixers and has been proposed as the sole or primary transport for HD-MIDI. The protocol is designed to be layered on top of UDP/IP and therefore will run over standard, inexpensive Ethernet and 802.11 (Wi-Fi) network links.
ACN relies on UDP in order to pass its messages. Where reliability is required, the Session Data Transport sub protocol allows semi-reliability of only the latest value for a particular "channel".
In practice
ACN will require a number of new technologies in order to implement it compared to the DMX512 standard. ACN requires the use of multicast Ethernet, so in larger networks, a switch that is IGMP snooping compatible will greatly improve performance.
Protocol architecture
ACN defines a number of sub protocols. These protocols all follow the TLV style Protocol Data Units (PDU). These can be nested in predefined hierarchy.
The Protocols defined in ANSI E1.17 are:
- Root Layer Protocol for UDP
- Session Data Transport Protocol (SDT)
- Device Management Protocol (DMP)
There is also an XML description language which defines properties of the devices which is called the Device Description Language.
Interoperability profiles
ACN is not closed in application. The protocol may be further defined via interoperability profiles which will extend various layers of the ACN stack, or define how elements of the ACN architecture must be used in a particular situation to achieve interoperability. For example, by providing specific values for timing parameters to be used in a particular network environment.
Implementations
E1.31 (Streaming DMX over ACN) is supported on Linux (ARM; i386, x86-64), and Macintosh (PowerPC; i386, x86-64) by the Open Lighting Architecture.
There is currently an OpenACN implementation project in progress which is hosted by SourceForge. This will provide open source library implementation which is intended to be portable to a variety of platforms from small embedded devices, to Windows and POSIX conformant operating systems.
External links
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