draft-ietf-core-multicast-notifications-proxy
Using Proxies for Observe Notifications as CoAP Multicast Responses
The Constrained Application Protocol (CoAP) allows clients to
"observe" resources at a server and to receive notifications as
unicast responses upon changes of the resource state. Instead of
sending a distinct unicast notification to each different client, a
server can alternatively send a single notification as a response
message over multicast, to all the clients observing the same target
resource. When doing so, the security protocol Group Object Security
for Constrained RESTful Environments (Group OSCORE) can be used to
protect multicast notifications end-to-end between the server and the
observer clients. This document describes how multicast
notifications can be used in network setups that leverage a proxy,
e.g., in order to accommodate clients that are not able to directly
listen to multicast traffic.