AT&T Deploys LwM2M Based IoT Device – Top 3 Lessons for IoT Developers

by OMA | Monday, April 17, 2017

Posted by Basavaraj Patil, Lead Member of Technical Staff with AT&T Mobility

The Internet of Things (IoT) is one of the fastest growing segments in the communications sector today. IoT touches almost every vertical segment that can be imagined including automotive, industrial, and healthcare. The ecosystem includes devices, networks, protocols, platforms, applications, analytics and more. All of these drivers have resulted in the equivalent of the wild west and the ecosystem runs the risk of deploying competing solutions, the consequence of which is that we end up with systems that do not interoperate.

The Open Mobile Alliance’s (OMA) LightweightM2M (LwM2M) protocol is a standards centric approach that has the potential of harmonizing the IoT ecosystem especially in the context of device management. Today, a number of protocols used by devices to communicate sensor or telematics type of data include MQTT, AMQP, HTTP, etc. LwM2M can be used in many scenarios as an alternative to some of these protocols. The protocol design considers the fact that many devices used in the IoT ecosystem are resource constrained. LwM2M is built on CoAP which was standardized in the IETF as a solution to address the resource-constrained module/device space. This protocol is attractive to the IoT ecosystem because it is open, standards based, and offers the ability to reuse a large set of well-defined objects. In addition to OMA defining a standard set of objects, the LwM2M Object Registry is open and other organizations such as IPSO have also specified large collections of objects. This enables rapid development and deployment.

Industry forecasts for the number of devices that will be connected by 2020 will exceed 20 billion. One of the critical aspects when looking at such large numbers of devices deployed globally is the ability to manage them and update firmware and software remotely. LwM2M offers device management capability that can enable operators and enterprises to manage a large and diverse ecosystem of devices. The protocol is designed to accommodate various modes of operation (UQS), depending on the type of network that the device operates on. It also takes into account the fact that devices could have very long sleep cycles and hence cannot be always on or reachable.

At AT&T, we are in the process of launching an IoT device that uses LwM2M for FOTA and device management in the 2nd quarter of 2017 and have learned a number of things during the development and testing process. A few key learnings are:

  1. LwM2M is very different from OMA-DM in terms of behavior and underlying transport protocol. The use of UDP as transport requires keep-alive messages that are sent every 2 minutes or less to ensure firewalls maintain state and allow packets to traverse.  The protocol from a behavior standpoint is server driven. The server commands the client to perform various actions.
  2. The various binding modes that the protocol specifies, i.e U(DP), Q(ueue) and S(MS) are confusing. On a cellular network where an IoT device is operating, we would not expect it to be always connected to the server and keeping a UDP/DTLS connection up. Clients must support UQS mode on cellular networks in order to optimize radio resources and limit traffic.
  3. The Observe/Notify behavior required in a client in order to delegate responsibility to the client for monitoring and reporting resource values needs to be much more specific and more emphasis placed on testing this functionality in interop test events.

LwM2M as a protocol is fairly new and hence has not been extensively adopted yet. Client and server implementations are in many cases interpreting the specification differently, resulting in a lack of interoperability. OMA TestFests and reference implementations of the client and server will no doubt help. But in the meanwhile there are growing pains. The protocol itself holds a lot of promise given its flexibility and a large pool of pre-defined objects to meet most IoT use cases. The implementation of the protocol and clients in devices and modules is growing and with that we do expect to see rapid growth in usage as well. From a cellular service provider perspective, we perceive the OMA LwM2M protocol as ideally suited for the IoT ecosystem.

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