A little over a year ago, the Zigbee Alliance joined with fellow IEEE 802.15.4 standards organization, The Thread Group in a demonstration of the former’s Dotdot application layer running on top of Thread’s networking stack.
Now, the pair have announced the completion of Dotdot specification v1.0, and the new Dotdot over Thread certification program. It’s been both a fast and slow year in the smart home, so maybe now is the time that Dotdot and Thread carve out a slice of the marketplace.
Apple joined Thread back in August, at the same time as the Zigbee Alliance was announcing it had passed the 500mn chips sold mark, and that it expected to account for 85% of 802.15.4 chip shipments – which doesn’t leave much room for Thread. If Apple is getting involved, then Thread might gain a bit more momentum, but the radio protocol does have a very big hill to climb against the venerable Zigbee, and even the similarly established Z-Wave.
The new argument is that the specification and certification program will allow developers to “confidently use a mature, open, and certifiable interoperability language over a low-power IP network. This will reduce product development risk and roadblocks, enable new IoT applications, and improve the consumer experience by reducing IoT fragmentation”.
We have asked before whether the two groups would be merging, as a couple of other overlaps in the IoT standards game have done in the past year, and have been told that there were no such plans. This is a shame, because when combined, the two camps are quite well fleshed out, while when viewed separately there are some weird omissions – most notably that Thread still needs to use Zigbee’s application layer (Dotdot) and that the grand-unification that was meant to be Zigbee 3.0 didn’t really clear up all the legacy clutter.
Still, as a combined entity, Thread-Dotdot is going to be useful, and so the progress the two groups have made is welcome. Thread’s certification program was slow to arrive, but hitching itself to Zigbee may well speed things up. The Zigbee Alliance points to Comcast’s Xfinity Home Security and Amazon Echo Plus as flagship devices, illustrating the power that a Zigbee hub can have in the home.
To this end, the two groups are pooling their testing resources, in an attempt to make up for list time. Thread’s mobile app for commissioning devices has been extended, to include application-level device configuration (the Dotdot bits), and an automated test harness is being touted as a way to expedite product development and certification preparations.
“Certification is critical to ensuring interoperability between wireless devices, but it can add time and complexity for product vendors,” said Grant Erickson, president of Thread Group. “Offering an efficient, affordable, and reliable certification process was a priority for both organizations and our members. As the Zigbee Alliance and Thread Group share a number of common authorized test labs, it made sense to streamline this go-to-market phase with a coordinated path to certification.”
When Dotdot was first unveiled, in January 2017, it was pushed as a way to create a universal language for IoT devices. In theory, any devices that was using Dotdot would be able to easily speak to other devices, as they shared that tongue, even if the other device was using a different radio.
Both Zigbee and Thread are IEEE 802.15.4-based mesh networking protocols. Zigbee has been in the market for some 15 years, and overhauled itself in the past couple of years to provide a more unified offering – of Zigbee 3.0 and its Zigbee Cluster Library (ZCL), rather than the handful of separate options that were available (Pro, GreenPower, RF4CE, etc). Thread is a much more recent arrival, growing out of Nest-Google but ticking many of the same boxes.
But Thread lacked an application layer, and so often used Zigbee’s – and it seems that this relationship eventually morphed into Zigbee making its application stack portable to other protocols – meaning that you could use the Dotdot application layer for other languages, such as Bluetooth or WiFi, and potentially things like LTE-M or NB-IoT.
The Zigbee Alliance calls Dotdot a universal language for the IoT, but it’s important to make clear that it is not a programming language. Zigbee can be made to work with IP messaging, but Thread is natively IPv6 compatible – which might remove a few head-scratchers from the development process. Both Thread and Zigbee use the same PHY and MAC layer, but Zigbee’s native networking layer is Pro.
Essentially, Dotdot defines how devices connect to networks and how they speak to other devices once they have joined. As long as a device is using Dotdot, it should be able to communicate with all other Dotdot devices on a shared network. While the Zigbee Cluster Library manages this for Zigbee, Dotdot is providing a way to do the same for other protocols – which has obvious benefits when it comes to IoT environments, as it means that WiFi devices should be able to communicate natively with Thread or Zigbee units.
“When the Zigbee Alliance announced Dotdot, the industry responded,” said Tobin Richardson, president and CEO of the Zigbee Alliance. “Over the last two years, companies from across the IoT worked together within the Alliance on this effort to take the interoperability standard at the heart of Zigbee and enable it to run over any network. Built from this solid foundation, we are excited to announce that the Dotdot spec is now prepared for ratification and release to Alliance members.”