In collaboration with the Broadcast Bridge, friend of the blog Andreas Hildebrand from ALC NetworX has written a 3 part guide to AES67, Broadcast Bridge have published part 1 with parts 2 and 3 to follow very soon.
What is AES67?
For a highly technical area of audio networking it's fair to say that awareness of AES67 is pretty widespread but in conversation with audio people, I think it's also fair to say that there is still a lot of confusion about exactly what it is and, just as importantly, what it isn't. I wrote a primer on AES67 some time ago AES67 - What Is It And Why Should You Care? and as a first place to go to orient yourself, this would be a good place to start. However, for some more detail this guide from Andreas is excellent and comes highly recommended.
The Same Old Acronyms
Systems like Dante and DiGiGrid offer an excellent solution for people who want to benefit from the advantages of AoIP but are happy to stay away from the underlying technology. However, for people who want to understand what is happening under the hood, I would suggest a working knowledge of AES67 is very worthwhile. All AoIP systems do the same job in slightly different ways but when you look into it, the same acronyms come up again and again as the same basic criteria for low latency, stable clocking, traffic management and discovery of streams all have to be addressed.
5 AoIP Acronyms
Do you recognise the following?
- IGMP Snooping
If not, don't be intimidated they are just some key technologies involved in AES67 and all address one of the basic criteria mentioned earlier. Network people, please excuse the following, these are supposed to be friendly explanations rather than definitions:
- Precision Time Protocol - just think word clock in a digital system and you won't be far off what this is.
- Quality of Service - Assigning levels of priority to different types of network traffic to make sure clocking happens properly and latency is acceptably low.
- Session Description Protocol - A way of connecting up audio streams between devices.
- Internet Group Management Protocol Snooping - A way of making sure that traffic intended for several users doesn't go to every user and cause a network traffic jam.
- Multicast Domain Name System/Real Time Streaming Protocol are the two systems used by RAVENNA (which AES67 is based on) to discover and connect devices to the network. Awkwardly Dante uses another system called SAP (Session Announcement Protocol) and this can make things more difficult though there is now software available which can help with this.
There's a lot in there but the point being made is that the same old subjects of Syncronisation, Transport, Quality of Service and Communicating Session Information come up again and again, the solutions can be difficult to understand but the issues they remedy are really simple. The best way to appreciate these, whichever AoIP system you intent to use, is to learn how AES67 can cross the divide between them.