In this third and final instalment of the AVB/TSN Spotlight we come to the issues facing AVB/TSN and the probable future direction of this technology. 

Interoperability

Interoperability is often an issue with non-proprietary solutions. If different manufacturers implement different subsets of the standards then the possibility of compatibility issues is high. The AVNU alliance has been set up to oversee compliance testing and certification to facilitate compatibility between different manufacturers. 

Update - Since the time of writing a new initiative from AVNU named Milan has been set up to address the compatibility issues between AVB products from different manufacturers.

Switches

The “Bridging” part of Audio Video Bridging refers to network switches. If AVB/TSN has a drawback it is the necessity of using AVB/TSN capable switches. The majority of installed switches in use today do not support AVB/TSN. Currently Extreme Networks, Arista Networks, Netgear and MOTU manufacture AVB/TSN capable switches but AVB/TSN capable switches are expected from Cisco and HP in the near future. Apart from the simple, relatively inexpensive MOTU switch most of these switches are enterprise level, managed switches and are priced accordingly. Development in this area has been slow and there is a familiar Catch 22 happening here where manufacturers seem to be waiting for demand for products from consumers who are waiting for products from manufacturers. This is far from a new phenomenon. The uptake of Thunderbolt was impeded by precisely the same situation. Frustratingly it appears that AVB/TSN functionality is being sold as a optional, paid licence for some switches, apparently many current switches could support AVB/TSN with a firmware update but progress in this area continues to be slow. Cisco are founding promoters of the AVNU alliance but are yet to support AVB/TSN in any of their switches.

TSN

Through AVB some important deficiencies in pre-existing networking protocols are addressed and deterministic, low latency performance can be of benefit to any user who would like to stop using dedicated point to point systems and carry all data on a network. Two of the biggest areas where this technology has potential are in industrial control systems and in automotive applications. Apparently the second heaviest component in a car, after the engine, is the wiring loom. AVB/TSN could potentially replace hundreds of discrete, point to point connections with a few metres of network cable. Of course there have to be guarantees that the instruction to switch on your brake lights gets to its destination quickly! This is where deterministic network behaviour becomes potentially life saving. In a similar way, being able to monitor and control an automated production line in a factory through cheap, scalable network control is very appealing but it needs the deterministic behaviour of AVB/TSN giving the guarantee that when an emergency stop button is hit the machine stops within a guaranteed period. To acknowledge the broader applications of technology which, although inspired by audio and video, has far wider applications the second generation of AVB has been renamed Time Sensitive Networking. TSN represents a refinement of AVB with even lower latencies available for priority messages (as low as a few hundred microseconds) and improved robustness in terms of redundancy and improved scalability. The additional features are unlikely to benefit smaller AV users but it’s important to realise that AVB is bigger than just audio and video and that TSN is the new name for AVB.

So AVB/TSN, while taking longer to establish itself than some of its competitors has a great deal going for it and has huge potential beyond AV. There’s plenty to think about here and I look forward to reading this in ten years time to see where we all end up. Many thanks to Jan Eveleens of Axon, Jim Cooper of MOTU and Chris Dixon for their advice and knowledge writing this series on AVB/TSN.