Thread Group recently hosted a virtual Panel Session Event regarding Thread’s role in IoT convergence and how that relates to the Project Connected Home over IP (CHIP) initiative driven by the Zigbee Alliance. It was an engaging and informative panel consisting of Thread Group Board Directors representing product companies and moderated by Bill Curtis from Moor Insights who wrote an article for Forbes about IoT, IP and Project CHIP. And, thanks to the great participation, we had dozens of insightful questions from the audience during the interactive portion of the webinar. Due to time constraints, we were unable to answer all questions so we put together this summary that categorizes and answers all audience questions.
Project Connected Home over IP: Detailed Questions
Several detailed questions were asked related to technical and certification areas. As stated, Project CHIP is an initiative within Zigbee Alliance. Details about goals, technical capabilities, resource requirements (memory, performance, security, etc.) and schedules will be communicated by the Zigbee Alliance. If your company is not a member of the Zigbee Alliance, and you want to be kept up-to-date about Project CHIP, please visit connectedhomeip.com and sign up for the interest list. Members of the Zigbee Alliance may participate in Project CHIP activities. Thread is in the market today and provides a secure implementation of IP including all the necessary ingredients for the application on top, it is ready for Project CHIP.
Transport Layers supported by Project CHIP
For questions related to the transport layers being supported by Project CHIP, connectedhomeip.com states, “The goal of the first specification release will be Wi-Fi, up to and including 802.11ax (aka Wi-Fi 6), that is 802.11a/b/g/n/ac/ax; Thread over 802.15.4-2006 at 2.4 GHz; and IP implementations for Bluetooth Low Energy, versions 4.1, 4.2, and 5.0 for the network and physical wireless protocols."
As an IPv6-bearing network layer, Thread can support one or more concurrent IPv6-based application layers. Consequently, Project CHIP products and the protocol(s) that they will run look just like IPv6 traffic to the Thread network, no different from LWM2M, Weave, Dotdot, or OCF. Thread technology will be a key ingredient for low power Project CHIP products.
Concerning Wi-Fi as a transport for Project CHIP, a question was received about “Wi-FI 6 target wake-up time (TWT)”. Particularly where wireless networks are concerned, adding support for Wi-Fi 6 TWT involves supporting the wireless network's authentication and on-boarding protocol. To the extent that Wi-Fi 6 TWT works like Wi-Fi 6 or earlier from an authentication and on-boarding perspective, then Wi-Fi 6 TWT should be easily supported by Project CHIP.
In regards to questions about the purpose of Bluetooth LE as one of the first transport layers supported, Project CHIP is targeted for IP networks with the following guidance from the website, "Some companies might focus their product offerings on the protocol over Wi-Fi/Ethernet, while others might target the protocol over Thread or Bluetooth LE, and still others might support a combination."
Since Project CHIP is defined for IP networks, using Bluetooth LE will require an IP adaptation. There have been various efforts over the years to define IP-bearing transport over Bluetooth and Bluetooth Low Energy with a number of draft RFCs circulated that detail some of those efforts. However, there has been little to no industry uptake or adoption of those efforts. Bluetooth LE has been used for out-of-band commissioning for Thread 1.1, and through investments from Thread Group members, Thread 1.2 includes Bluetooth LE support natively.
Gateways & Cloud
An interesting question about gateways, “There’s a balance between the simplicity of stateless gateways and the requirement for state for features like mirroring which is necessary for intermittently connected devices that only wake up infrequently.” How Project CHIP will address this requirement is being defined by the Project CHIP Working Group. Concerning Thread, a Thread Group member company has implemented “digital twinning” into its ecosystem’s technology.
Regarding what role the cloud plays in Project CHIP and “whether or not it will be a critical role in the design, or at least go further than Thread to define how to depend and/or interact with the cloud”, the same is true as above - this scope is part of the Project CHIP Working Group’s efforts.
Network
Network disconnections are a reality, especially with battery powered devices that stay in deep sleep to minimize power for a large percentage of the time they are on the network. Thread supports the notion of a sleepy end device (SED) which may sleep with its Tx/Rx off for an implementation-defined period of time which may span from seconds to days.
This stack illustrates Project CHIP will likely incorporate support for UDP over IP with some minimal end-to-end application layer reliability facility which should accommodate SEDs. A Thread Group member, Google, has experience and success with such constructs of UDP over IPv6 with Thread SEDs.
Certification
Thread has an active certification program that provides an official, independent proof-point of the product or component’s functional conformance to the Thread specification and interoperability performance with market-leading Thread reference implementations. Project CHIP certification will be determined by the Project CHIP Working Group. However, it is possible that Thread certification could become a prerequisite for Project CHIP as well as other app layers. Thread Group and Zigbee Alliance have several common test houses to provide a seamless certification experience, Bureau Veritas (7-Layers), DEKRA, TUV Rheinland, and UL.
Thread: Specific Questions
Network Expansion
Thread 1.1 currently limits the number of routers to 32, but each router can theoretically support up to 511 children, allowing for thousands of Thread devices in a single network.
Thread supports efficient any-to-any routing by employing a distance-vector routing protocol. A key parameter in the performance of any given distance-vector routing protocol is the number of routers. Thread made a concerted tradeoff in choosing the number of routers. Limiting the number of routers provides many benefits. It improves routing protocol efficiency, by limiting routing protocol state, communication overhead, and convergence time. It also improves multicast forwarding efficiency, by limiting the set of devices that participate in forwarding a multicast message.
A key part of the Thread infrastructure is the Border Router. See our recent blog on the role the Border Router plays in the network, how it works and example Border Routers available in the market today.
By supporting IP, Thread networks can be seamlessly integrated into a larger network composed of IP-based links (including Ethernet, Wi-Fi, Cellular, etc.). Thread Border Routers are IP routers that connect Thread networks to other IP-based networks. Similar to Wi-Fi access points, Thread Border Routers are application agnostic.
In order to communicate IPv6 messages between Thread devices and other devices on the LAN via Thread Border Routers, the IPv6 network needs to be properly configured (as with any IP-based network) for devices to communicate end-to-end. IPv6 global-scope addresses are necessary for communicating across different IPv6 links. Global-scope addresses may be Unique Local Address [RFC 4193] or globally routable on the public Internet. Global-scope addresses may be configured using IPv6 SLAAC or DHCPv6.
Thread 1.2 introduces a new feature that supports connecting multiple Thread networks into a single IPv6 subnet via Thread Backbone Routers attached to the same Ethernet or Wi-Fi link, similar to large Wi-Fi deployments with multiple access points. This allows for almost limitless scalability without jeopardizing network performance. It also provides the benefit of responsive and efficient routing topologies while supporting larger IPv6-based networks simultaneously. Devices can even roam between networks while keeping their domain IP address (See Thread 1.2 in Commercial White Paper).
Thread + One (or Many)
Thread is designed to carry IPv6 traffic on the network and, by extension, to egress IPv6 traffic out of and into the Thread mesh through simple IPv6 routing. Consequently, Thread works with Wi-Fi networks through the use of a Border Router that performs the simple IPv6 routing function. To the extent that the Wi-Fi network contains IPv4-only devices, the Border Router may have to perform and manage other functionality (for example, NAT64 and DNS64) to allow communication with such devices.
Thread also works with Bluetooth LE by defining point-to-point Bluetooth LE central/peripheral links as a new physical interface over which Thread traffic can be carried. As already described, Thread 1.2 supports Bluetooth LE for commissioning devices to a Thread network and to connect a smart device, via Bluetooth LE, with a Thread network for direct interactions on that network. More detailed information is available to Thread Group Contributor or higher members in the draft Thread 1.2 Bluetooth Extensions specification.
Thread: Low Power and Security
In addition to being based on the low power protocol IEEE 802.15.4, Thread has other energy-related functionality integrated (see Thread’s Value of Low Power White Paper). As a communication protocol, Thread is primarily responsible for managing power of the IEEE 802.15.4 radio and employs multiple low-power communication techniques from IEEE 802.15.4. Thread 1.1 uses IEEE 802.15.4 indirect transmissions that allows devices to achieve very low duty-cycles by periodically polling their parent to receive messages. Thread 1.2 (see Thread 1.2 Base Features White Paper) introduces the ability for sleepy end devices to use IEEE 802.15.4-2015 Coordinated Sampled Listening (CSL), allowing even lower duty-cycles and/or communication latency. Managing power of other system components is left to other components, including the application and/or operating system.
Security is a core component of Thread. Thread mesh networks are always secure, authentication is required for a device to join the network and all data that flows over the mesh network is encrypted with an always-rotating key that is unique to each mesh with no pre-shared, global state or secret. What is done with the application data is ultimately the responsibility of application developers and ecosystems.
Thread 1.2
Thread 1.2 is designed to improve the scalability of Thread networks, by making them more responsive, and capable of a higher network density. New, previously-described low power features further reduce the power consumption, channel utilization and communication latency of sleepy end devices. In addition, Thread 1.2 includes optional features with Commercial and Bluetooth LE Extensions to expand the use cases Thread can serve. The Thread 1.2 specification is available now to Thread Group members. Thread 1.2 certification is scheduled to be available mid-year, Bluetooth and Commercial Extensions certification available by the end of 2020.
Summary
Many great topics were covered by our moderator and panelists in the panel-session webinar and expanded upon through the audience questions captured in this blog. Thread Group sees the Project Connected Home over IP effort driven by the Zigbee Alliance as an accelerator for IoT adoption and another affirmation on the value of IP. Since Thread is available today, we envision work being done in the Project CHIP Working Group to include Thread to ensure Thread + Project CHIP will be ready when Project CHIP is available.
As we look forward, we encourage companies and organizations who are not part of Thread Group, to join (various membership options including one for academia) and work with other members to develop or monitor further enhancements to Thread, a low-power IP-based network technology, supporting new use cases related to and in addition to those targeted by Project CHIP. As a network layer technology that’s agnostic to the applications, future enhancements are open for any interested application.