DANTE NETWORKING BASICS
Intended primarily for use in professional and commercial audio environments, DANTE is a combination of hardware and software used to transport multi-channel, digital audio over a standard IP over Ethernet network.
DANTE is developed by Audinate Pty. Ltd. The company sells hardware and software. Audinate licence other manufacturers to use the DANTE system, so as a result, there are (as of Autumn 2015) over 500 products with integrated DANTE compatible hardware, from over 170 manufacturers.
The multiple channels are combined by multiplexing prior to transmission, audio is uncompressed, latency is low and may be set by the user. the system may be used in the presence of other IP traffic. A personal computer is used to configure the network, using the DANTE Controller software. After configuration, the computer may be removed until needed for re-configuration or analysis purposes.
The DANTE (Digital Audio Network Through Ethernet) system provides syncronisation throughout all the DANTE-enabled devices on a network, conducting the traffic so that the audio remains 'in sync' as is essential, see Digital Audio Over Ethernet Networks. The system has the ability to pass through routers and configures itself automatically to assign one of the DANTE-enabled 'hosts' on the network as the 'master' for syncronisation purposes.
DANTE audio channels can be configured as unicast or multicast as appropriate, to make best use of available bandwidth. Unicast provides a direct point-to-point stream for unique groups of channels; multicast sends an audio stream to multiple devices simultaneously. By default data packets are sent using unicast, but the user can change this to multicast.
DANTE systems can 'easily scale from a simple pairing of a console to a computer, to large capacity networks running thousands of audio channels. Because DANTE uses logical routes instead of physical point-to-point connections, the network can be expanded and reconfigured at any time with just a few mouse clicks.' Each gigabit Ethernet link can transport up to 512 channels in each direction at 48kHz sampling. The maximum sampling rate is 192kHz and the maximum bit-depth is 32 bits. DANTE can use networks constructed with higher link-speeds, such as 10Gb/s. The number of possible channels per link increases proportionately.
Essentially, the network is built and the DANTE devices are connected. Using the DANTE Controller software application, running on an attached PC, the devices on the network are configured. Devices will be discovered and displayed on screen. Connections between devices are made virtually, by connecting cross-points in an on-screen diagram. Device names and channel labels may be edited, sample rates controlled, and device latencies set. A single audio channel is 'referred to just like an email address: "leadVocal @ StageBoxSL" or "chairmans_mic @ conferenceroomA". Once the network is configured, the computer running DANTE Controller can be removed from the network, and reconnected only if changes are required or system monitoring is desired. Signal routing and other system settings are stored safely in the DANTE devices themselves, so they are automatically restored if a device is power-cycled.'
The DANTE Controller is a free software application to configure devices on a DANTE network and to manage audio routes, with 'automatic device discovery, one-click signal routing and user-editable device and channel labels'. It also provides 'real-time network monitoring functionality, including multicast bandwidth usage, latency monitoring, clock status monitoring and configurable event logging, enabling you to quickly identify and fix potential issues on the network.'
This may be downloaded at no charge: www.audinate.com, where the software is described in more detail.
The DANTE Virtual Sound card uses the Ethernet port on a PC or Mac computer to communicate with a network of other DANTE enabled devices. No auxiliary hardware is required. The computer becomes a DANTE workstation, to record, process and playout using 'any audio application and any combination of DANTE-enabled devices' A trial version may be downloaded at no charge. Licenses are available for 7-day and 30-day temporary use as well as a permanent licence.
Implementation - Wiring
The network is configured, as is a standard Ethernet network, in a star configuration with a network switch (not a hub) at the centre, with separate cables out to each host or secondary switch. Fibre optic connections can be used. If there are only two DANTE devices, they may be connected directly to each other, without a switch.
The maximum copper cable length for each switch to host should not exceed 100 metres, including network patching and leads to the installed sockets. Category 5E or Cat6 cable is recommended, although Cat5 may be used for 'purely 100Mbps networks'. Connectors are RJ45, as in a standard Ethernet installation.
Implementation - Wireless
'While possible in principle, the practical limitations of current wireless technology (802.11a/b/g/n) render reliable performance unachievable. For this reason DANTE software such as Virtual Sound card will not recognize wireless connections for audio data.'
Implementation - Network Switches
A gigabit switch is recommended but is not a absolute requirement for a small system. 'As a rule of thumb, total bandwidth utilisation (including multicast and unicast) on any given link should not exceed 70% of the supported bandwidth for any link' (on an unmanaged network without QoS implementation; see below). 'Utilisation above 70% of supported bandwidth can adversely impact clock synchronization' (in such circumstances) '(especially if there is also non-DANTE traffic on the network)'.
The DANTE system has three categories of data which are passed over the network. The first category is timing information which allows the system to syncronise the delivery of the different audio streams. The second is the actual audio and the third is other control data. Since the system 'relies on timing data to maintain syncronisation, the preferred switch will be a 'managed' type, with the provision to set 'QOS' (quality of service) priority for the different types of traffic, the timing information being set as the highest and other network traffic set as the lowest priority.'
Quality of Service (QoS) is a feature of many managed switches, which ensures that certain types of network packets (e.g. clock sync and audio packets) get preferential treatment and are "moved to the front of the line" ahead of other traffic. This is achieved by attaching a priority number to each packet, which is then used by the switches to ensure that high priority packets get processed before lower priority packets. DANTE implements DSCP QoS (as used by VoIP systems) which has higher granularity, and therefore more control than legacy CoS style implementations.
While Gigabit switches are recommended, 100Mbps switches may be used in limited circumstances,
For channel-counts of 32 or more, Gigabit switches are highly recommended. QoS implementation is highly when using DANTE in networks that have 100Mbps devices. QoS is also recommended for Gigabit switches on networks that share data with services other than DANTE. For lower channel count (less than 32) applications, a 100Mbps switch may be used; as previosly stated, appropriately configured QoS is highly recommended. The use of 100Mbps switches without QoS is not recommended or supported.'
Any switches with the following features should be appropriate for use with DANTE:
- Gigabit ports for inter-switch connections
- Quality of Service (QoS) with 4 queues
- Diffserv (DSCP) QoS, with strict priority
- A managed switch is also recommended, to provide detailed information about the operation of each network link: port speed, error counters, bandwidth used, etc.'
(Note: Those not experienced in adjusting managed switches with the often-used, RS232 port might wish to purchase a switch which is managed via a web interface.)
'Green Ethernet' or 'EEE (Energy Efficient Ethernet)' switches should not be used in a DANTE network.
Audinate explain: 'EEE (Energy Efficient Ethernet) is a technology that reduces switch power consumption during periods of low network traffic. It is also sometimes known as Green Ethernet and IEEE802.3az. Although power management should be negotiated automatically in switches that support EEE, it is a relatively new technology, and some switches do not perform the negotiation properly. This may cause EEE to be enabled in DANTE networks when it is not appropriate, resulting in poor synchronisation performance and occasional dropouts.'
They advise: 'If you use managed switches, ensure that they allow EEE to be disabled. Make sure that EEE is disabled on all ports used for real-time DANTE traffic. If you use unmanaged switches, do not use Ethernet switches that support the EEE function, because you cannot disable EEE operation in these switches.'