Thread provides extensive support for low-power operation using sleepy end nodes. As the name would suggest, these sleepy devices are meant to spend the majority of their time in a low-power sleep state. With Thread, sleepy devices are not required to check in with the network, enabling prolonged battery life. Messages for sleepy devices are buffered by their parents. Message transmission is triggered only after a sleepy device wakes up and polls its parent for any inbound messages.
Thread was architected with the specific goal of supporting networks of 250+ nodes. With this constraint, features and capabilities were adapted to maximize throughput and minimize resource requirements. In a Thread network, the maximum number of active routers is 32. A direct and important consequence of this is that routing information can be efficiently distributed across the network and all routers are able to maintain visibility of all routes within the network. As nodes are added to the network and the topology changes, the network adapts by exchanging Mesh Link Establishment (MLE) messages. Additional routers can be autonomously added if there are Router Eligible devices operating as end devices. Such Router Eligible end devices or REEDs, listen to routing messages and will petition the Leader of the network to become a router if determined necessary to improve the overall performance of the network.
Thread is a robust, self-healing mesh network that offers no single point of failure. If a router fails, the network will dynamically re-route traffic around the failed node. If a Leader fails, another router on the network will be autonomously elected the new Leader. Multiple border routers can be used to provide fail-safe redundancy for off-network communication.
The Thread Group has contracted a standard test harness to be used for certification of all Thread stacks as well as final Thread products. This test harness will be provided to all Thread member companies to allow high quality development and testing of software prior to Thread certification testing.
All Thread components (ICs, software stacks or modules) must be certified as Thread compliant before being used in an end product by a customer. All end product devices that want to carry the Thread logo must submit their devices for laboratory certification at an approved test lab.
Thread networks are built to be simple to use yet extremely secure. Thread uses AES-128 to protect all networking transactions at the MAC level and utilizes a combination of ECC and J-PAKE algorithms to securely add devices to a network (i.e. commissioning). Applications have the option to utilize standards-based IP security protocols (e.g., DTLS) to additionally secure application payloads.
The Thread network assumes that there is a commissioning device available for a user to designate to add new devices to the Thread network. Thread makes it possible to designate both off-network devices such as smart phones and computers and on-network Thread devices to become commissioners.
Off-network devices must first petition with a Thread Border Router to become a registered commissioner using a secure DTLS authentication handshake specified by Thread. Once registered, the Border Router then performs arbitration with the Leader on behalf of the commissioner candidate to become an authorized commissioner. On-network devices do not require registration, but may need to perform arbitration with the Leader to be authorized. (The Leader ensures that only one commissioner is active on the network at a time.) Once authorized, the active commissioner will be made known throughout the Thread network.
To join, a user instructs the commissioning device that a new devices is to be added and inputs a unique passphrase associated with the joining device. This passphrase is used to establishing a secure DTLS session to authenticate and authorize the joining device. Only then is the device provided access to the Thread network. Once the device is added to the network, the commissioning device is no longer active.
Thread makes its place in the IoT by providing a wide array of benefits that make the connected home, in particular, easier to design for, manage, secure and expand. Find out more at www.bitly.com/THREADWP.
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