Back in the seventies the Palo Alto Research Center in California, USA (www.parc.com) developed some nifty computer technology such as the mouse, the laser printer and computer networks. From the first versions of networks such as Aloha-Net and ARPA-Net the Internet has evolved. Robert Metcalfe, first working at PARC and later founding his own company 3COM, developed a practical networking standard for use in offices called Ethernet. More than 40 years later the whole world is using this standard to build information systems, and all personal computers, smart phones, tablets and also many professional audio products sold today have some form of Ethernet port built in. The Ethernet protocol is standardized as 802.3 by the IEEE standards organization.
The basic building blocks of Ethernet networks are network interface cards (NIC, built into devices such as computers, digital mixers), cables to connect them to the network, and switches; devices that tie all cables in a network together and take care of the correct routing of all information through the network. The operating speed of these building blocks, determining how much information a network can carry, has evolved from 10 Megabits per second in 1972 to one Gigabit per second and higher in 2018.
Ethernet works by dividing information streams into small packets and then sending them over the network to a certain receiver address specified by the sender. Every Network Interface Card (NIC) has an address, and switches keep lists of addresses connected to the network in their memory so they know where to send packets. Every NIC in the world has a unique Media Access Control (MAC) address programmed by the manufacturer. There are 280 trillion different MAC addresses, and there is only one company in the world, the IEEE standards organization, that allocates these addresses to manufacturers. This way all MAC addresses of all NICs in the world are unique: there are no doubles. Throughout the years, the control of MAC addressing by the IEEE was maintained rigorously, resulting in Ethernet to have grown to one of the most prevalent and reliable standards in the world, used for almost anything: from smartphones to fridges, from headphones to cars, instituting the Internet of Things (‘IoT’). Experts estimate that the IoT will consist of about 30 billion objects by 2020.
In addition to MAC addresses, a ‘user definable’ addressing layer is used to make network management easier for local networks. This additional user address is called the Internet Protocol address, short named ‘IP’ address. The IP address is normally 4 bytes long (‘IPv4’), a 16 byte IP address was introduced (‘IPv6’) in 2008 because the amount of devices active on the internet had outgrown the 4 byte address range. For industrial networks however, including audio networks, the 4 byte version is still used.
Many other standards were built upon the Ethernet standard over the years such as IEE802.1 Virtual Local Area Networks (VLAN), IEEE1588 Precision Time Protocol (PTP), IEEE802.11 Wireless Local Area Networking (WLAN, aka WiFi). Along with the Ethernet protocol standards, also cabling standards have evolved. The most prevalent cable used is CAT5E, standardized by the American National Standards Institute (ANSI) as ANSI/TIA/EIA-568-A.
From a professional audio viewpoint, amazingly, it seems as if Ethernet is geared for building infrastructures for professional digital audio systems. First, Ethernet is capable of transporting huge amounts of raw data over a network; the 2018 basic port data rate for even small inexpensive switches is 1 Gigabit (Gb) per second, supporting up to 512 channels of 24-bit 48KHz audio, which is enough for the majority of even large scale audio systems. Second, the speed of an average Gigabit Ethernet based audio connection is usually below 0,125ms – which is totally acceptable even for live audio applications. Third, the CAT5E cable standard supports cable lengths up to 100 meter which is perfect for most audio systems. When larger distances are needed, optical connections can be used for lengths even up to several kilometers.
It didn’t take long for professional audio companies to discover Ethernet’s fitness for use. In 1996, Peak Audio (US) introduced Cobranet and in 2001, Digigram (France) introduced Ethersound. Both standards are based on 100Mb Ethernet that was the standard in these years. After the basic Etnernet port speed evolved to Gigabit, several companies introduced advanced high capacity audio network protocols, of which Audinate’s Dante became the most used standard.