Proxy Operations in Group Communication for the Constrained Application Protocol (CoAP)

This document defines a specific realization of proxy intended for scenarios that use group communication for the Constrained Application Protocol (CoAP). Such a proxy processes a single request sent by a client typically over unicast and distributes the request to a group of servers, e.g., over UDP/IP multicast as the defined default transport protocol. Then, the proxy collects the individual responses from those servers and relays those responses back to the client, in a way that allows the client to distinguish the responses and their origin servers through embedded addressing information. This document updates RFC7252 with respect to caching of response messages at proxies.