Coap caching

The protocol supports the caching of responses in order to efficiently fulfill requests. Simple caching is enabled using freshness and validity information carried with CoAP responses. A cache could be located in an endpoint or an intermediary. Caching functionality is specified in Section 5.6.

Proxying is useful in constrained networks for several reasons, including to limit network traffic, to improve performance, to access resources of sleeping devices, and for security reasons. The proxying of requests on behalf of another CoAP endpoint is supported in the protocol. When using a proxy, the URI of the resource to request is included in the request, while the destination IP address is set to the address of the proxy. See Section 5.7 for more information on proxy functionality.

As CoAP was designed according to the REST architecture [REST], and thus exhibits functionality similar to that of the HTTP protocol, it is quite straightforward to map from CoAP to HTTP and from HTTP to CoAP. Such a mapping may be used to realize an HTTP REST interface using CoAP or to convert between HTTP and CoAP. This conversion can be carried out by a cross-protocol proxy ("cross-proxy"), which converts the Method or Response Code, media type, and options to the corresponding HTTP feature. Section 10 provides more detail about HTTP mapping.