Lightweight M2M (LwM2M)

OMA Lightweight M2M (LwM2M) is a protocol for machine to machine (M2M) or Internet of things (IoT) device management and service enablement. It was designed for sensor networks and the demands of a machine-to-machine (M2M) environment and specified at the Open Mobile Alliance (OMA) SpecWorks Device Management Working Group.

Protocol scope:

• Device management, including remote provisioning of security credentials, firmware updates, remote device diagnostics and troubleshooting.
• Service enablement, including sensor and meter readings, remote actuation and configuration of host devices.

Documents & Resources

Did you know?

The specifications are best source of informations! Don’t let yourself be overwhelmed. Open the table of contents and jump directly to the sections you need.

A good introduction is provided by the LwM2M v1.1 slides,

Documents:

• Lightweight Machine to Machine Technical Specification: Core (1.2.1 / 2022-12-09)
• Lightweight Machine to Machine Technical Specification: Transport Bindings (1.2.1 / 2022-12-09)
• Lightweight Machine to Machine Requirements (1.2 / 2020-11-10)

Useful links:

• OMA Technical Dashboard
  • Object and Resource Registry
  • Object schema v1.1 (LWM2M-v1_1.xsd)
• Introduction slides (LwM2M v1.1)

Architecture overview

The whole system is called LwM2M Enabler has two components. The LwM2M Server and the LwM2M Client. The LwM2M Device acts as a Client and the M2M service, platform or application acts as the Server.

Source: Technical Specification: Core v1.2.1

Interfaces

Four interfaces are designed between these two components.

• Bootstrap
• Client Registration
• Device management and service enablement
• Information Reporting

Note

The Bootstrap interface and server are not in the scope of this project!
We are going to register Clients with a pre-defined Server.

Each of these interfaces is related to a set of operations.

Operations

The operations can be classified into uplink operations and downlink operations. The uplink operatations are initiated by the device and the downlink operations are initiated by the server. They are mapped to protocol mechanisms in the LwM2M Transport specification.

Interface	Direction	Operation
Bootstrap	Uplink	Bootstrap-Request, Bootstrap-Pack-Request
Bootstrap	Downlink	Bootstrap-Write, Bootstrap-Read, Bootstrap-Discover, Bootstrap-Delete, Bootstrap-Finish
Client Registration	Uplink	Register, Update, De-register
Device Management and Service Enablement	Downlink	Create, Read, Read-Composite, Write, Delete, Execute, Write-Attributes, Write-Composite, Discover
Information Reporting	Downlink	Observe, Observe-Composite, Cancel Observation, Cancel Observation-Composite
Information Reporting	Uplink	Notify, Send

Resource Model

The LWM2M Enabler defines a simple resource model. Relationships between Resources, Objects, and the Client are illustrated in the following figure.

Source: Technical Specification: Core v1.2.1

• Each piece of information made available by the LWM2M Client is a Resource.
• Resources are logically organized into Objects.
• The Client may have any number of Resources, each of which belongs to an Object.
• Resources are defined per Object, and each Resource is given a unique identifier within that Object.
• Resources and Objects have the capability to have multiple instances of the Resource or Object, called Object Instance and Resource Instance.
• Each Object and Resource is defined to have one or more operations that it supports.