RFC 7252

RFC 7252
Title	RFC 7252
Status	Proposed Standard
Published	June 2014
Authors	Carsten Bormann, Zhen Cao
Pages	38
Area	Internet protocols
Related	Constrained Application Protocol, CoAP, IETF

RFC 7252

RFC 7252 defines the Constrained Application Protocol (CoAP) as a web transfer protocol for constrained nodes and constrained networks. It specifies message formats, request/response interactions, URI mapping, and content negotiation intended for resource-limited devices in environments like Internet of Things deployments, IEEE 802.15.4 networks, and integration with Representational State Transfer paradigms. The document is an outcome of work within the Internet Engineering Task Force and ties to efforts in organizations such as the Internet Architecture Board and IETF Constrained RESTful Environments.

Background

CoAP was developed to bridge constrained devices in contexts such as Zigbee, 6LoWPAN, and Bluetooth Low Energy to web architectures championed by figures and groups like Roy Fielding and the World Wide Web Consortium. Early motivations trace to interoperability with protocols from ETSIng, IETF ROLL, and practical deployments involving vendors like ARM Holdings and research at institutions such as Fraunhofer Society and MIT. The protocol addresses requirements highlighted in meetings hosted by Internet Engineering Task Force working groups, driven by standardization bodies including the IAB and influenced by experiments in projects funded by agencies like the European Commission and programs at National Institute of Standards and Technology.

Specifications

RFC 7252 details message formats, including a compact binary header and options mechanism comparable in spirit to the mappings in Hypertext Transfer Protocol while tailored to small footprint stacks used by vendors such as TI and Silicon Labs. It defines methods analogous to HTTP verbs and content formats aligned with IANA registries and media type registrations advocated by the IETF Applications Area. The specification maps CoAP URIs to representations compatible with systems like Uniform Resource Identifier schemes and aligns with registries maintained by the Internet Assigned Numbers Authority. Compression and block-wise transfer features reference techniques used in protocols influenced by work at Carnegie Mellon University and ETH Zurich.

Protocol Operations

CoAP operations include confirmable and non-confirmable messaging, retransmission strategies, and observer patterns resembling publish/subscribe concepts used in systems by Eclipse Foundation projects and research at ABB. The protocol supports proxies, caching behaviors, and multicast similar to practices in Multicast Listener Discovery and routing protocols from groups such as IETF ROLL and Open Networking Foundation. Interactions are described for constrained devices deployed in scenarios involving companies like Siemens and Schneider Electric and integrated with platforms supported by Amazon Web Services and Microsoft Azure for IoT backends. Constrained endpoints implement message layer state machines with timers and congestion control influenced by recommendations from the Internet Engineering Task Force congestion control research community.

Security Considerations

RFC 7252 addresses security through DTLS bindings and considerations for object security approaches paralleling work by researchers at University of California, Berkeley and ETH Zurich. It outlines authentication, confidentiality, and integrity strategies interoperable with profiles such as those from the IETF Security Area and mechanisms developed by the Open Web Application Security Project community. Operational security concerns include key management and trust anchors similar to practices in Public Key Infrastructure deployments and guidelines from organizations like the National Institute of Standards and Technology. Threat models reference attack classes studied by academic groups at Stanford University and industry teams at Cisco Systems.

Implementations and Adoption

Implementations of the protocol appear in stacks from open-source projects like those hosted by the Eclipse Foundation and commercial products from manufacturers including Samsung Electronics, Bosch, and Panasonic. Community implementations stem from repositories and research labs at University of Strathclyde and INRIA and have been integrated into firmware for platforms by ARM Cortex-M vendors and modules from Espressif Systems. Adoption in standards and ecosystems includes alignment with frameworks from oneM2M, interoperability events run by Open Connectivity Foundation, and deployments in smart city initiatives coordinated with municipalities and companies such as IBM and Schneider Electric.

History and Revisions

The document evolved from earlier drafts and experimental deployments documented within IETF mailing lists and meetings chaired by contributors affiliated with institutions like Universität Bremen and Huawei Technologies. Revisions incorporated feedback from interoperability tests run at events organized by the IETF CoRE Working Group and industry consortia including the Zigbee Alliance and AllSeen Alliance. Subsequent extensions and related RFCs, produced after the original publication, address security profiles, group communication, and observability enhancements with participation from stakeholders such as Google, Apple Inc., and research centers like ETH Zurich.

Category:Internet protocols