5.1 Required Features

This clause explicitly specifies the required features of the CoAP layer for oneM2M to properly bind oneM2M primitives into CoAP messages:

• The 4-byte binary CoAP message header is defined in section 3 of IETF RFC 7252 [1].
• Confirmable (CON), Non-confirmable (NON), Acknowledgement (ACK) and Reset (RST) messages shall be supported. The Reset message is used to send an error message in response to a malformed Confirmable message in CoAP layer.
• GET, PUT, POST and DELETE methods shall be supported, as shall the FETCH method defined in IETF RFC 8132 [6]. oneM2M primitives map to these methods.
• The CoAP Response Codes specified in clause 6.2.4 shall be supported for oneM2M Response Status Code parameter mapping.
• The Uri-Host, Uri-Port, Uri-Path, and Uri-Query shall be supported.
• The Content-Type Option shall be used to indicate the media types of the payload.
• Block-wise transfers feature may be supported to carry large payloads.
• The Caching feature may be supported.