Sleepy CoAP Nodes
6LoWPAN networks rely on application protocols like CoAP to enable RESTful communications in constrained environments. Many of these networks make use of "Sleepy Nodes": battery powered devices that switch off their (radio) interface during most of the time to conserve battery energy. As a result of this, Sleepy Nodes cannot be reached most of the time. This fact prevents using normal communication patterns as specified in the CoRE group, since the server-model is not applicable to these devices. This document discusses and specifies an architecture to support Sleepy Nodes such as battery-powered sensors in 6LoWPAN networks with the goal of guiding and stimulating the discussion on Sleepy Nodes support for CoAP in the CoRE WG.