How It’s Done: Digital Audio Networks

AV and IT convergence has moved beyond trend to reality. The lines of responsibilities for AV system installations are now blurred between the IT manager and the audio engineer.

A decade ago, an idea to use standard IT networks for the transport of high quality media developed into a new networking solution based on industry standards. Called Dante, it is an uncompressed, multi-channel digital media networking technology that ‘packetizes’ and segments the audio, and wraps it in IP (Internet Protocol) packets suitable for transmission across an Ethernet network. The packets contain timing information and source and destination network addresses. When the corresponding device receives the audio packets, it reconstructs them back into a continuous digital audio stream.

Dante is architected from four networking technology building blocks. A Dante network can be setup by simply plugging the devices into Ethernet switches, making the system “Plug-and-play”. By integrating Zero-configuration Networking (Zeroconf), all the advantages of a managed network with Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS) services are present.

Dante devices automatically assign network addresses to themselves, eliminating the need for setting Static IP Addresses. Network administrators no longer need to manually set up services, such as Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS). Alternatively, standard DHCP and DNS protocols are applied when they are available in a network.

All devices and audio channels are referred to using simple, user-editable, friendly names. Dante integrates multicast DNS (mDNS) and DNS Service Discovery (DNSSD) protocols for discovery and enumeration, using these standards to automatically discover each other on the network and eliminating the need to manually enter device addresses into each device.

To guarantee very low latency, low jitter and sub-microsecond synchronization over Gigabit networks, Precision Time Protocol (PTP) — formally defined by the IEEE as IEEE1588 - is used to synchronize clocks throughout a network. Dante uses PTP to synchronize the high-quality clocks contained in each device to a single clock master on the network. All devices are synchronized to +/- 1 microsecond, resulting in the delivery of sample accurate playback with extremely low latency and jitter.

IP, as the primary protocol in the Internet layer of the Internet Protocol suite, has the task of delivering packets from the source to the destination solely based on the IP addresses in the packet headers.

By using IP, Dante uses the same standards as all other network traffic that you would see in existing networks. This has the advantage of allowing the use of standard networking equipment, including “off-the-shelf” switches.

While an unmanaged network switch can be used for Dante networks, configuring a managed switch will allow you to achieve higher channel counts and best performance from the network.

There are two techniques commonly employed on modern managed networks. The first technique is to use Quality of Service (QoS). In almost all modern Ethernet switches, this will be a version of QoS called DSCP (Differentiated Services Code Point), or DiffServ.

DiffServ is a QoS networking tool that specifies a simple, scalable, and coarse-grained method for classifying and managing network traffic. DiffServ can, for example, be used to provide low-latency to critical network traffic such as voice or streaming media while providing simple best-effort service to non-critical services, such as web traffic or file transfers. Dante devices automatically mark the traffic that should be highest priority, and it is easy to configure switches to prioritize that traffic.

The second technique is to make use of Internet Group Membership Protocol (IGMP). IGMP is a communications protocol used to establish multicast group memberships. The feature allows a network switch to listen in on the IGMP conversation on the network, and then filter IP multicast from the links that do not need it.

Installing a digital audio network doesn’t need to be perplexing, as it takes advantage of the same protocols and techniques already used in standard IP networks. Technology managers with a basic understanding of the IT network can very quickly have a reliable and scalable architecture in place capable of moving many channels of audio across facilities, campuses and venues, with high quality and low latency.

Lee Ellison is the CEO of Audinate.