Architecture for Control Networks (
ACN) is a suite of network protocols for theatrical control being developed by ESTA (Entertainment Services and Technology Association). 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/IPThe User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...
and therefore will run over standard, inexpensive
EthernetEthernet is a family of frame-based computer networking technologies for local area networks . The name comes from the physical concept of the ether...
and 802.11 (Wi-Fi) network links.
ACN relies on
UDPThe User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...
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".
ACN In Practice
ACN will require a number of new technologies in order to implement it compared to the
DMXDMX512-A is an EIA-485 based communications protocol that is most commonly used to control stage lighting and effects. It was originally intended as a 'lowest common denominator' protocol for use between interfaces supporting proprietary protocols...
standard. ACN requires the use of
multicastMulticast addressing is a network technology for the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split.The word...
ethernet, so in larger networks, a switch that is
IGMPThe Internet Group Management Protocol is a communications protocol used to manage the membership of Internet Protocol multicast groups.IGMP is used by IP hosts and adjacent multicast routers to establish multicast group memberships....
snooping compatible will greatly improve performance.
Protocol Architecture
ACN defines a number of sub protocols. These protocols all follow the
TLVWithin data communication protocols, optional information may be encoded as a type-length-value or TLV element inside of the protocol.The type and length fields are fixed in size , and the value field is of variable size...
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 & Macintosh 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
POSIXPOSIX or "Portable Operating System Interface [for Unix"] is the name of a family of related standards specified by the IEEE to define the application programming interface , along with shell and utilities interfaces for software compatible with variants of the Unix operating system, although the...
conformant operating systems.
External links