Network Working Group C. Bormann Internet-Draft Universitaet Bremen TZI Intended status: Informational J.J. Jimenez Expires: 24 September 2020 Ericsson 23 March 2020 CoRE Working Group -- Overview draft-bormann-core-overview-00 Abstract The IETF "Constrained RESTful Environments" (CoRE) Working Group standardizes application layer protocols that can be used by resource-constrained devices, as can be found in the Internet of Things (IoT). It is part of a cluster of about a dozen IETF WGs defining specifications for these environments. This short document provides an overview of the activies of the CoRE WG as of end of March, 2020. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 24 September 2020. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components Bormann & Jimenez Expires 24 September 2020 [Page 1] Internet-Draft CoRE Working Group -- Overview March 2020 extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Main Specification . . . . . . . . . . . . . . . . . . . . . 2 3. Security . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Operations and Management . . . . . . . . . . . . . . . . . . 3 5. Data Formats . . . . . . . . . . . . . . . . . . . . . . . . 4 6. Further Information . . . . . . . . . . . . . . . . . . . . . 4 7. Informative References . . . . . . . . . . . . . . . . . . . 4 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction The IETF "Constrained RESTful Environments" (CoRE) Working Group standardizes application layer protocols that can be used by resource-constrained devices, as can be found in the Internet of Things (IoT). It is part of a cluster of about a dozen IETF WGs that define networking (e.g., 6Lo), routing (e.g., ROLL), and security (e.g., ACE, LAKE, SUIT) for these environments. This cluster has been growing since 2005; ten years ago, on 2010-03-09, CoRE was added to it. 2. Main Specification The main specification of CoRE is the Constrained Application Protocol (CoAP) [RFC7252]. CoAP is for applications including constrained devices what HTTP is for general purpose applications. By using UDP as the transport protocol as opposed to HTTP's use of TCP, and by removing much of the baggage of of HTTP, CoAP can be run on quite simple platforms and with very little power use. Both protocols share the Representational State Transfer (REST) architecture, the same set of verbs (GET, PUT, POST, DELETE), and quite similar semantics. Since CoAP's approval in 2013, further specifications have been added to support the Observe pattern of change notifications from a server (low-complexity server-push) [RFC7641], to support larger transfers [RFC7959], to add verbs (FETCH, PATCH, and idempotent iPATCH [RFC8132]), and to enable the use of CoAP over TCP [RFC8323]. [RFC8768] recently added a way to detect and mitigate loops in a proxy configuration, motivated by the requirements of the Distributed Denial-of-Service Open Threat Signaling (DOTS [I-D.ietf-dots-signal-channel]) specification. Bormann & Jimenez Expires 24 September 2020 [Page 2] Internet-Draft CoRE Working Group -- Overview March 2020 Two further extensions are now in completion: reducing the need for per-request state in clients and proxies [I-D.ietf-core-stateless] (in IETF last call) and improving the security between multiple active requests [I-D.ietf-core-echo-request-tag], further reducing CoAP's exploitability in denial of service attacks (completed working-group last call). 3. Security Security has always been a critical enabler for IoT. Similar to the way the HTTP web uses TLS, CoAP was kicked off with a security architecture based on Datagram TLS (DTLS), which provides high levels of security, but does not support end-to-end security in a configuration that includes proxies. Object Security for CoRE (OSCORE) now provides end-to-end security over proxy paths that may include both CoAP and HTTP [RFC8613]. One interesting aspect of OSCORE is that it also supports group communication, as it occurs in multicasting requests to collect responses from a group of nodes. CoAP has supported multicast requests from the outset, and [RFC7390], Group Communication on top of IP multicast, provides additional specfication for this. As DTLS only supports unicast, without a security architecture RFC 7390 was published an experimental RFC. Work is now underway to revise this RFC [I-D.dijk-core-groupcomm-bis], which includes making use of the capabilities provided by OSCORE for group communication [I-D.ietf-core-oscore-groupcomm]. Work is now under way in the CoRE, ACE, and LAKE working groups to complement this basis with additional specifications making use of OSCORE and CoAP group communication. 4. Operations and Management IoT systems need to support a large number of nodes, which need to be configured and integrated into an IoT system. A discovery and self- description architecture based on web links has been the first product of the WG [RFC6690], which is now being complemented by a registration and discovery function (CoRE Resource Directory [I-D.ietf-core-resource-directory], in IESG processing). Constrained nodes also need management functions. While many IoT SDOs are integrating these right into their IoT data format specifications, the IETF has its own architecture for describing management information, YANG [RFC7950]. The "CORECONF" specifications that are in Working Group Last Call (including YANG- CBOR [I-D.ietf-core-yang-cbor]) make this widely used approach of providing management interfaces available in a highly efficient way that is applicable to constrained environments, as our complement to the established YANG protocols NETCONF and RESTCONF. Bormann & Jimenez Expires 24 September 2020 [Page 3] Internet-Draft CoRE Working Group -- Overview March 2020 5. Data Formats While CoAP can be used with many different data formats, a simple CoRE format for sensor and actuator data, Sensor Measurement Lists (SenML), was defined in [RFC8428]. Recently, a number of specifications have been readied in support of SenML that are now undergoing final processing by the RFC editor: Support for the RFC 8132 verbs [I-D.ietf-core-senml-etch], and modifications to the SenML units registry [I-D.ietf-core-senml-more-units] that make it more accessible as a basis for data format standards of other Standards Development Organizations (SDOs). A foundation for further data format specification that combines the web-linking approach of RFC 6690 with more modern data representation techniques is now being worked on under the name CoRAL [I-D.ietf-core-coral]; application specifications such as CoAP pubsub [I-D.ietf-core-coap-pubsub] are expected to pivot to this basis. 6. Further Information To follow and contribute to CoRE's work, please refer to the core status page (https://tools.ietf.org/wg/core/ (https://tools.ietf.org/wg/core/)) and join the core mailing list: _core@ietf.org_ via https://www.ietf.org/mailman/listinfo/core (https://www.ietf.org/mailman/listinfo/core). 7. Informative References [I-D.dijk-core-groupcomm-bis] Dijk, E., Wang, C., and M. Tiloca, "Group Communication for the Constrained Application Protocol (CoAP)", Work in Progress, Internet-Draft, draft-dijk-core-groupcomm-bis- 03, 9 March 2020, . [I-D.ietf-core-coap-pubsub] Koster, M., Keranen, A., and J. Jimenez, "Publish- Subscribe Broker for the Constrained Application Protocol (CoAP)", Work in Progress, Internet-Draft, draft-ietf- core-coap-pubsub-09, 30 September 2019, . [I-D.ietf-core-coral] Hartke, K., "The Constrained RESTful Application Language (CoRAL)", Work in Progress, Internet-Draft, draft-ietf- core-coral-03, 9 March 2020, . Bormann & Jimenez Expires 24 September 2020 [Page 4] Internet-Draft CoRE Working Group -- Overview March 2020 [I-D.ietf-core-echo-request-tag] Amsuess, C., Mattsson, J., and G. Selander, "CoAP: Echo, Request-Tag, and Token Processing", Work in Progress, Internet-Draft, draft-ietf-core-echo-request-tag-09, 9 March 2020, . [I-D.ietf-core-oscore-groupcomm] Tiloca, M., Selander, G., Palombini, F., and J. Park, "Group OSCORE - Secure Group Communication for CoAP", Work in Progress, Internet-Draft, draft-ietf-core-oscore- groupcomm-07, 9 March 2020, . [I-D.ietf-core-resource-directory] Shelby, Z., Koster, M., Bormann, C., Stok, P., and C. Amsuess, "CoRE Resource Directory", Work in Progress, Internet-Draft, draft-ietf-core-resource-directory-24, 9 March 2020, . [I-D.ietf-core-senml-etch] Keranen, A. and M. Mohajer, "FETCH & PATCH with Sensor Measurement Lists (SenML)", Work in Progress, Internet- Draft, draft-ietf-core-senml-etch-07, 9 March 2020, . [I-D.ietf-core-senml-more-units] Bormann, C., "Additional Units for SenML", Work in Progress, Internet-Draft, draft-ietf-core-senml-more- units-06, 19 March 2020, . [I-D.ietf-core-stateless] Hartke, K., "Extended Tokens and Stateless Clients in the Constrained Application Protocol (CoAP)", Work in Progress, Internet-Draft, draft-ietf-core-stateless-05, 12 March 2020, . [I-D.ietf-core-yang-cbor] Veillette, M., Petrov, I., and A. Pelov, "CBOR Encoding of Data Modeled with YANG", Work in Progress, Internet-Draft, draft-ietf-core-yang-cbor-12, 9 March 2020, . Bormann & Jimenez Expires 24 September 2020 [Page 5] Internet-Draft CoRE Working Group -- Overview March 2020 [I-D.ietf-dots-signal-channel] Reddy.K, T., Boucadair, M., Patil, P., Mortensen, A., and N. Teague, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification", Work in Progress, Internet-Draft, draft-ietf-dots-signal-channel- 41, 6 January 2020, . [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link Format", RFC 6690, DOI 10.17487/RFC6690, August 2012, . [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained Application Protocol (CoAP)", RFC 7252, DOI 10.17487/RFC7252, June 2014, . [RFC7390] Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for the Constrained Application Protocol (CoAP)", RFC 7390, DOI 10.17487/RFC7390, October 2014, . [RFC7641] Hartke, K., "Observing Resources in the Constrained Application Protocol (CoAP)", RFC 7641, DOI 10.17487/RFC7641, September 2015, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in the Constrained Application Protocol (CoAP)", RFC 7959, DOI 10.17487/RFC7959, August 2016, . [RFC8132] van der Stok, P., Bormann, C., and A. Sehgal, "PATCH and FETCH Methods for the Constrained Application Protocol (CoAP)", RFC 8132, DOI 10.17487/RFC8132, April 2017, . [RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K., Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained Application Protocol) over TCP, TLS, and WebSockets", RFC 8323, DOI 10.17487/RFC8323, February 2018, . Bormann & Jimenez Expires 24 September 2020 [Page 6] Internet-Draft CoRE Working Group -- Overview March 2020 [RFC8428] Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C. Bormann, "Sensor Measurement Lists (SenML)", RFC 8428, DOI 10.17487/RFC8428, August 2018, . [RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz, "Object Security for Constrained RESTful Environments (OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019, . [RFC8768] Boucadair, M., Reddy.K, T., and J. Shallow, "Constrained Application Protocol (CoAP) Hop-Limit Option", RFC 8768, DOI 10.17487/RFC8768, March 2020, . Acknowledgements Marco Tiloca provided comments on a draft of this document. Authors' Addresses Carsten Bormann Universitaet Bremen TZI Postfach 330440 D-28359 Bremen Germany Phone: +49-421-218-63921 Email: cabo@tzi.org Jaime Jimenez Ericsson Email: jaime.jimenez@ericsson.com Bormann & Jimenez Expires 24 September 2020 [Page 7]