6.1 Introduction

When AE or CSE binds oneM2M primitives to CoAP messages, or binds CoAP messages to oneM2M primitives, it is required that:

• AE shall host a CoAP client and should host a CoAP server; or
• CSE shall host both a CoAP client and a CoAP server.

In general a single oneM2M request primitive is mapped to a single CoAP request message, and a single oneM2M response primitive is mapped to a single CoAP response message. However, a single oneM2M request/response primitive is mapped to multiple CoAP request/response messages respectively when the CoAP block-wise transfer feature is used.

Mapping between CoAP message and oneM2M primitive shall be applied in the following cases:

• when the Originator sends a request primitive;
• when the Receiver receives a CoAP message(s);
• when the Receiver sends a response primitive;
• when the Originator receives a CoAP message(s).

The following sub-clauses specify how to map each oneM2M primitive parameter defined in oneM2M TS-0004 [2] to a corresponding CoAP message field to compose a CoAP request/response message.