Hitachi (China) Research and Hitachi (China) Research and China Mobile CoAP utilizes DNS to discovery the IP address of the CoAP server. However DNS is heavy for the most resource constrained end-points. In this case the assistance from CoAP proxy or research directory (RD) is needed for CoAP transaction. This specification proposes to define one new dhcp option for proxy/RD discovery for the most resource constrained end-points.