Internet DRAFT - draft-bormann-core-overview
draft-bormann-core-overview
Network Working Group C. Bormann
Internet-Draft Universität Bremen TZI
Intended status: Informational J. Jiménez
Expires: 1 October 2020 Ericsson
30 March 2020
CoRE Working Group -- Overview
draft-bormann-core-overview-01
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 activities of the
CoRE WG as of end of March, 2020.
About This Document
This document is not intended for publication as an RFC. It provides
a snapshot of the current status of the WG, from the personal view of
the authors. The intention is to keep it updated, roughly once per
physical IETF meeting (or its digital replacement).
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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 1 October 2020.
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Copyright Notice
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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.
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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.
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 specification 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.ietf-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).
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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.
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]
[I-D.ietf-core-href]; 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.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,
<http://www.ietf.org/internet-drafts/draft-ietf-core-coap-
pubsub-09.txt>.
[I-D.ietf-core-coral]
Hartke, K., "The Constrained RESTful Application Language
(CoRAL)", Work in Progress, Internet-Draft, draft-ietf-
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core-coral-03, 9 March 2020, <http://www.ietf.org/
internet-drafts/draft-ietf-core-coral-03.txt>.
[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, <http://www.ietf.org/internet-drafts/draft-
ietf-core-echo-request-tag-09.txt>.
[I-D.ietf-core-groupcomm-bis]
Dijk, E., Wang, C., and M. Tiloca, "Group Communication
for the Constrained Application Protocol (CoAP)", Work in
Progress, Internet-Draft, draft-ietf-core-groupcomm-bis-
00, 30 March 2020, <https://www.ietf.org/internet-drafts/
draft-ietf-core-groupcomm-bis-00.txt>.
[I-D.ietf-core-href]
Hartke, K., "Constrained Resource Identifiers", Work in
Progress, Internet-Draft, draft-ietf-core-href-03, 9 March
2020, <http://www.ietf.org/internet-drafts/draft-ietf-
core-href-03.txt>.
[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, <http://www.ietf.org/internet-
drafts/draft-ietf-core-oscore-groupcomm-07.txt>.
[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, <http://www.ietf.org/internet-drafts/draft-
ietf-core-resource-directory-24.txt>.
[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,
<http://www.ietf.org/internet-drafts/draft-ietf-core-
senml-etch-07.txt>.
[I-D.ietf-core-senml-more-units]
Bormann, C., "Additional Units for SenML", Work in
Progress, Internet-Draft, draft-ietf-core-senml-more-
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units-06, 19 March 2020, <http://www.ietf.org/internet-
drafts/draft-ietf-core-senml-more-units-06.txt>.
[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, <http://www.ietf.org/internet-drafts/draft-
ietf-core-stateless-05.txt>.
[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,
<http://www.ietf.org/internet-drafts/draft-ietf-core-yang-
cbor-12.txt>.
[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, <http://www.ietf.org/internet-drafts/
draft-ietf-dots-signal-channel-41.txt>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/info/rfc6690>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>.
[RFC7390] Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for
the Constrained Application Protocol (CoAP)", RFC 7390,
DOI 10.17487/RFC7390, October 2014,
<https://www.rfc-editor.org/info/rfc7390>.
[RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015,
<https://www.rfc-editor.org/info/rfc7641>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
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[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/info/rfc7959>.
[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,
<https://www.rfc-editor.org/info/rfc8132>.
[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,
<https://www.rfc-editor.org/info/rfc8323>.
[RFC8428] Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
Bormann, "Sensor Measurement Lists (SenML)", RFC 8428,
DOI 10.17487/RFC8428, August 2018,
<https://www.rfc-editor.org/info/rfc8428>.
[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,
<https://www.rfc-editor.org/info/rfc8613>.
[RFC8768] Boucadair, M., Reddy.K, T., and J. Shallow, "Constrained
Application Protocol (CoAP) Hop-Limit Option", RFC 8768,
DOI 10.17487/RFC8768, March 2020,
<https://www.rfc-editor.org/info/rfc8768>.
Acknowledgements
Marco Tiloca provided comments on a draft of this document.
Authors' Addresses
Carsten Bormann
Universität Bremen TZI
Postfach 330440
D-28359 Bremen
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
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Jaime Jiménez
Ericsson
Phone: +358-442-992-827
Email: jaime@iki.fi
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