Required Features

For realization of the LWM2M interfaces, only the basic binary CoAP message header, and a small subset of options are required. This section explicitly defines the features of the CoAP standard that are required for LWM2M.

• The 4-byte binary CoAP message header is defined in Section 3 of [CoAP]. This same base message is used for Request and Response interactions.
• Confirmable, Acknowledgement and Reset messages MUST be supported. The Reset message is used as a message layer error message in response to a malformed Confirmable message. Non-Confirmable messages MAY be used by a Client for sending Information Reporting notifications as per [Observe].
• GET, PUT, POST and DELETE methods MUST be supported. LWM2M Operations map to these methods.
• A subset of Response Codes MUST be supported for LWM2M response message mapping.
• The Uri-Path Option MUST be supported to indicate the identifier of the interface, Object Instance and Resource being requested.
• The Location-Path Option MUST be supported to indicate the handle of a registration for future update and delete operations.
• The Uri-Query Option MUST be supported.
• The Content-Type Option MAY be used to indicate the media type of the payload. A default value of plain/text is assumed, allowing this option to be elided for most payloads.
• The Token Option MAY be used to enable multiple requests in parallel with an endpoint, and MUST be supported for the Information Reporting interface.